Secondary Air Injection FAQ for Toyota & Lexus Owners

If your Toyota or Lexus has thrown a secondary air injection code, gone into limp mode, or sounds like a vacuum cleaner on a cold start; we are glad you found Hewitt Technologies. The following is a collection of answers to the most frequently asked SAIS questions. Below we provide explanation of system, most common codes, what it costs to fix, and if a Hewitt Technologies Bypass Kit is the right solution for you. Hewitt Technologies is the creator of the original and most trusted SAIS bypass kits for Toyota and Lexus vehicles. Our products our proudly made in the USA (Lexington, SC) since our founding in 2014. Can’t find your question? Call (844) 307-7671, Monday to Friday 8:30 am to 5:00 pm ET we actual enjoy talking to our customers. Or submit a contact form.

Jump to: The basics · Fault codes · Symptoms and safety · Fixes and cost · Legality and emissions · Fitment and products · Installation and after · Buying from Hewitt

The basics

What is the Secondary Air Injection System (SAIS) on a Toyota or Lexus?

The Secondary Air Injection is an emissions control system that pumps fresh air into the exhaust for a short time after a cold start. It’s sole purpose is to promote combustion of unburned carbon prior to catalytic convertor heating up to operating temperature. Toyota and Lexus fitted it to their larger trucks and SUVs between 2005 – 2024 model years, across Tundras, Sequoias, Tacomas, 4Runners, FJ Cruisers, Land Cruisers, GXs and LXs.

It is a supporting system, not a primary one: it assists the catalytic converters by providing ambient air to oxygen depleted exhaust. Unlike the older belt-driven smog pumps, it does not run all the time. It runs once, for well under two minutes, at a cold-soak start, meaning the first start after the engine has been off for seven hours or more. The SAIS consists of electric air pump(s), air switching valve(s), pressure sensor(s), and air injection control driver(s). It is not a question of “If” the SAIS is going fail but “When”. This failure prone system is the weak link in an otherwise very reliable vehicle.  Longer explanation: What is the Secondary Air Injection System?

What does the secondary air injection pump do, and when does it run?

The air pump pushes outside air into the exhaust manifolds for roughly 20 to 90 seconds after a cold-soak start, while the engine is running rich and the catalytic converters are still cold. The air switching valves open to let that air in, then close to keep hot exhaust out of the pump and sensors.

You will usually hear it: a whir or whoosh from the engine bay for the first half-minute or so on a cold morning is normal. The system does not run on warm restarts. Flex Fuel 5.7L trucks and all 2014 and newer vehicles also run the pumps briefly at shutdown to clear condensation out of the system, and so do 2012 and 2013 5.7L Tundras and Sequoias that received Toyota updated ECM calibration. That shutdown cycle matters when you choose a bypass kit: only the Gen 2 kits handle it (see “Which kit fits my vehicle?”).

Where are the secondary air injection pump and valves located?

This will vary based on engine size and model year. Below you will find a list of engine sizes along with model year ranges. The corresponding links will provide engine layouts.

Which Toyota and Lexus models have a secondary air injection system?

Toyota and Lexus began implementing the Secondary Air Injection System beginning in model year 2005. Primarily installed on their larger V8 engines on the Tundra, Sequoia, Land Cruiser, 4Runner V8, GX470, GX460, LX470 and LX570. The system is less common but can also can be found on select years of V6 and four-cylinder models including Tundra, Tacoma, 4Runner and FJ Cruiser.

Hewitt Bypass kits are compatible with the following Year / Model / Engie Sizes:

• 4.7L V8 (2UZ-FE): Tundra 2005–2009, Sequoia 2005–2009, 4Runner 2005–2009, Land Cruiser 2006–2007, Lexus GX470 2005–2009, Lexus LX470 2006–2007
• 5.7L V8 (3UR-FE): Tundra 2007–2021, Sequoia 2008–2022, Land Cruiser 2008–2021, Lexus LX570 2008–2021
• 4.6L V8 (1UR-FE): Tundra 2010–2019, Sequoia 2010–2012, Lexus GX460 2010–2023
• 4.0L V6 (1GR-FE): Tundra 2007–2014, Tacoma 2012–2015, 4Runner 2013–2024, FJ Cruiser 2013–2014
• 2.7L four-cylinder (2TR-FE): Tacoma 2005–2023, 4Runner 2010–2011, Hilux 2005–2025 (non-US)

Within the V6 and four-cylinder ranges, some trucks were built without the system depending on their emissions certification, so use the Search by Vehicle tool on this site to confirm your exact year, model and engine. We are also working on compiling layout for International models that differ from North American market. If you do not see your vehicle your vehicle listed please do not hesitate to give us a call.

Fault codes

P2440 and P2442: what does “air switching valve stuck open” mean, on Bank 1 or Bank 2?

P2440 means the ECM sees exhaust pressure at the Bank 1 air switching valve when the valve should be closed, so it reports the valve stuck open; P2442 is the same fault on the Bank 2 valve. P2440 is the single most common SAIS code on the Toyota Tundra, Tacoma, Sequoia and 4Runner, and the stuck-open codes are the ones that most often put the truck in limp mode. Valve Stuck Open codes can also mask a pressure sensor that is damaged or not reading within specification.

A valve that is physically stuck open can expose the pressure sensor to hot exhaust or moisture, which can damages the pressure sensors over time. For this reason it is important to address the codes quickly, repeatedly clearing of codes and continued driving will result in need for additional Bypass Kit equipment. Four-cylinder trucks, which have a single bank, only ever report P2440; engines with two valves can set either code. A Gen 1 or Gen 2 bypass kit with the block-off plates installed clears both codes and keeps them off, and the plates matter most here, because they seal a leaking valve away from the pressure sensor. Full write-ups: P2440 explained and P2442 explained.

P2441 and P2443: what does “air switching valve stuck closed” mean, on Bank 1 or Bank 2?

P2441 means the ECM saw no pressure change at the Bank 1 air switching valve when it commanded the valve open, so it reports the valve stuck closed; P2443 is the same fault on Bank 2. Despite the name, these codes usually have nothing to do with the valve: about 80 percent of the failures Hewitt sees start with a worn air pump that can no longer build pressure, which the ECM reads as a valve that did not open.

A worn pump often announces itself first with the vacuum-cleaner noise on cold starts, and once its motor fails electrically P0418 or P0419 appears as well. Because a closed valve keeps exhaust out of the system, these codes do not carry the sensor-damage risk of the stuck-open codes. Engines with a single bank only report P2441. A Gen 1 or Gen 2 bypass kit with the block-off plates installed clears both codes and keeps them off; if the pump has already died electrically, the Gen 2 handles that on its own and a Gen 1 needs one Pump Proxy Pack per code. 

P2445 and P2447: “air pump stuck off” on Bank 1 or Bank 2

P2445 means the ECM commanded the Bank 1 air pump on at a cold start and the pressure sensor did not see it run; P2447 is the same for Bank 2. The usual cause is a pump whose impeller or motor has worn out, or a blown air pump fuse.

Check the air pump fuse before condemning the pump. If the motor itself has failed you will often see P0418 or P0419 alongside. A Hewitt bypass kit clears P2445 and P2447 when they appear only at cold start; a blown fuse or a damaged pressure sensor has to be dealt with at the same time for the kit to work. One exception to know about: on some 2005 and 2006 4.7L vehicles, starting the engine at or below freezing and then driving above 50 mph in that same drive cycle can set P2445 through an ECM glitch, with or without a bypass kit, and even with a brand-new factory system. Toyota’s fix was a reflash campaign that is no longer available. The workaround is to start, let the temperature gauge move off cold, shut down and restart before driving over 50 mph, or simply clear the code when it happens. Details are on the codes page.

P2444 and P2446: “air pump stuck on”

P2444 (Bank 1) and P2446 (Bank 2) mean the ECM detected pressure at the air injection pressure sensor when the pump was supposed to be off. The pump is rarely running by itself; more often a switching valve that is leaking exhaust is pressurizing the sensor, or the pump’s relay or driver circuit has failed closed.

These codes are much less common than the stuck-off codes and usually appear with a valve-stuck-open code, which points at the valve. A Gen 2 bypass kit addresses them because it replaces the air injection drivers and stops the system being commanded at all; the block-off plates isolate the leaking valve. If P2444 or P2446 persists after a kit and plates are installed, suspect a damaged pressure sensor (see “Do I need the pressure sensor add-on?”).

P2431, P2432, P2433, P2436, P2437, P2438 and P106B: the pressure sensor codes

These codes mean one of the air injection pressure sensors is reading out of range: P2431 to P2433 for the Bank 1 sensor, P2436 to P2438 for Bank 2, and P106B when the two SAIS sensors and the evaporative pressure sensor disagree about atmospheric pressure. They are caused by sensor damage, not by the pump or valves, and they are the fastest-growing SAIS codes on 2010 and newer Tundras and Sequoias.

The sensors sit inside the air switching valves on 2007 and newer vehicles, close to the exhaust. A valve that stays stuck open for long enough lets hot, moist exhaust reach the sensor and damages it. A bypass kit alone cannot clear these codes: the ECM still needs working pressure sensors. Add a pressure sensor add-on to the kit, which replaces the damaged sensor’s signal without replacing the expensive valve: the Pressure Sensor Jumper, Replacement Harness or Replacement Double for Gen 1 kits, or the Gen 2 pressure sensor add-on (PSO). P106B has a catch: its test only runs once no valve codes are present, so it can appear for the first time after a bypass kit has cleared everything else. Comparing the freeze-frame data for the three sensors shows which one is wrong.

P0418 and P0419: air pump relay circuit codes

P0418 means an open or short circuit in the Bank 1 air pump circuit and P0419 the same on Bank 2. In practice they mean the air pump motor has failed electrically, or its fuse has blown, or the wiring has been damaged (rodents are a regular culprit).

These are the codes that follow the “vacuum cleaner” noise once the pump motor finally gives up. The Gen 2 bypass kit clears P0418 and P0419 on its own, because it replaces the air injection drivers that monitor the pump circuits. The Gen 1 kits cannot, unless you add one Pump Proxy Pack per code; the pack plugs in at the air injection driver and stands in for the dead pump, so the old pump can stay where it is.

P0412, P0415, P0416 and P0417: switching valve circuit codes

These are electrical codes for the air switching valve solenoids: P0412 is an open or short in the Bank 1 valve’s solenoid circuit, P0415 the same for Bank 2, and P0416 and P0417 report the Bank 2 valve circuit open or shorted. Unlike P2440 to P2443 they say nothing about whether the valve is moving; the ECM simply cannot complete the circuit to the solenoid coil.

The usual cause is a failed solenoid coil, or corrosion, chafing or rodent damage in the harness between the air injection driver and the valve. The Gen 2 bypass kit clears these codes by itself. The Gen 1 kits need one Valve Solenoid Pack per code, which plugs in at the driver connector and lets the driver see what it thinks is a healthy solenoid, so the valve under the intake manifold on a 4.7L never has to come out.

P1613, P1614, P1441, P1442, P1444, P1445 and the other SAIS codes

P1613 and P1614 mean the air injection control driver itself has failed (Bank 1 and Bank 2); P1441, P1442, P1444 and P1445 are the stuck-open and stuck-closed codes for the No. 2 air switching valve on each bank, found on vehicles with two valves per side.

The driver codes are common on the 5.7L and 4.6L trucks, which carry two drivers. Because the Gen 2 kit replaces the drivers outright, it addresses P1613 and P1614; the Gen 1 kits work through the factory driver and do not. The P144x valve codes behave like P2440 to P2443 and are cleared by either kit with the block-off plates installed. You may also meet P0410, P0411, P0491 or P0492, the generic “secondary air flow” codes used by other manufacturers; they are uncommon on the Toyota and Lexus engines Hewitt supports, which report the specific codes above, so if your scanner shows one, read the codes again with a Toyota-capable tool. The complete list, grouped by what clears it, is on the codes page.

Which side of the engine is Bank 1 and which is Bank 2?

Bank 1 is the cylinder bank that contains cylinder number one. On the Toyota and Lexus V8s that is the passenger side of the engine in a US vehicle, so Bank 1 codes such as P2440, P2441 and P2445 point at the passenger-side valve and pump, and Bank 2 codes such as P2442, P2443 and P2447 point at the driver’s side.

Four-cylinder and V6 engines with a single valve only report Bank 1. Toyota’s own parts labels do not say “Bank 1” or “Bank 2”; the air pumps on the 5.7L and 4.6L V8s even share a single part number for both positions, with the bank distinction coming from the wiring, not the hardware. On a 4.7L the “No. 1” and “No. 2” switching valves are different part numbers. The installation instructions for each engine show which connector is which.

Symptoms and safety

What is limp mode, and can I keep driving with a SAIS code?

Limp mode is the fail-safe the ECM drops into when a monitored system fails: throttle is limited to about 50 percent, Vehicle Stability Control and Traction Control are switched off, the engine runs on baseline fuel maps instead of live sensor data, and the transmission may shift oddly. On these trucks it is most often triggered by a valve-stuck-open code (P2440, P2442, P1441 or P1444), and C1201 is stored alongside to record that VSC and TRAC were disabled.

The SAIS itself does no harm to the engine when it fails; it only works for a minute or so after a cold start. The danger is limp mode: a Tundra that will not go over 35 to 40 mph and has no stability control is unsafe on a highway. If you are stuck somewhere, clearing the code with a scanner or by disconnecting the battery for about five minutes gets you home, because the system only runs again at the next cold-soak start. Treat that as a way to get home, not a fix: every time the system runs with a stuck valve, hot exhaust reaches the pressure sensors, and repeated clearing is how a cheap repair turns into a sensor replacement too.

Why does my Toyota sound like a vacuum cleaner for 30 seconds when I start it cold?

That is the secondary air injection pump, and the noise means it is failing. A healthy pump makes a soft whoosh for the first 20 to 45 seconds of a cold start; a loud vacuum-cleaner or electric-motor grind is the pump vanes rubbing the housing or the motor bearings going.

For most owners this is the first sign of trouble, before any code appears. It rarely lasts long: once the noise starts, the pump motor usually fails completely within days or weeks and sets P0418 or P0419, sometimes with P2445 or P2447. Fitting a bypass kit while the pump is still electrically alive is cheaper, because a dead pump motor needs the Gen 2 kit or a Gen 1 kit plus a Pump Proxy Pack. If you hear this sound and have no codes yet, you are in the best position you will be in.

Can a failed air pump or stuck switching valve damage the engine?

No. The secondary air injection system is connected only to the exhaust, so a failed pump or a stuck valve cannot damage the engine, transmission or catalytic converters. The only parts at risk are the system’s own pressure sensors.

When a switching valve is physically stuck open or leaking, hot, moisture-laden exhaust flows back to the pressure sensor built into the valve and eventually damages it. The 2007 to 2009 Tundra 4.7L and every 2010 and newer vehicle are the most susceptible because their sensors sit closer to the exhaust. A damaged sensor turns a bypass-kit repair into a bypass kit plus a pressure sensor add-on, which is why Hewitt recommends installing the kit and the block-off plates as soon as the first code appears rather than clearing codes for a season. The engine, meanwhile, is fine; limp mode is a safety limiter, not a sign of mechanical damage.

How do I tell whether the pump, a valve or a pressure sensor has failed?

Start with the code and a simple test. About 80 percent of the failures Hewitt sees are the air pump wearing out, which shows up as valve-stuck-open codes, the vacuum-cleaner noise, or P2445/P2447, and eventually P0418/P0419 when the motor fails electrically.

The test: clear the codes after the first start of the day, when the system has already run. If the truck stays clear all day and the code returns on the next cold start, the pump is the cause and a standard bypass kit without add-ons will handle it. A valve-stuck-open code that will not clear with the engine off, or that returns after a kit and block-off plates are installed, means a damaged pressure sensor. A pressure sensor circuit code (P2431 to P2438) or correlation code (P106B) also means sensor damage. P0412, P0415, P0416 and P0417 point at the valve solenoid wiring; P1613 and P1614 at the driver module. If you have freeze-frame data, the pressure readings for the two SAIS sensors and the evap sensor tell you which sensor is lying. Hewitt’s support line can usually tell you what you need from the codes and a few questions before you order.

Fixes and cost

How much does it cost to repair or replace the secondary air injection system at a Toyota or Lexus dealer?

Dealer quotes for an SAIS repair on a Toyota or Lexus V8 typically run $2,000 to $3,000 for parts and labor, and go higher when both air pumps and the switching valves are replaced together. On the 4.7L engines the pump and main valve sit under the intake manifold, so most of the bill is labor.

The parts are not cheap either: factory air pumps are several hundred dollars each and the 5.7L and 4.6L V8s need two, and the valve assemblies are in the same range. Owners regularly report dealer and independent-shop quotes of $2,300 to $3,500, and much higher in Canada. Replacing the parts also does not change the design that failed, so a new pump can fail the same way. Cheap aftermarket pumps and valves fail faster still and are often replaced two or three times under their own warranty. A Hewitt bypass kit with block-off plates costs a fraction of a dealer repair, installs in an afternoon, and carries a limited lifetime warranty. A side-by-side comparison is in the kit comparison post.

What are my options: Dealer Repair vs Replacement Parts vs Bypass Kit?

There are four routes. A dealer repair with factory parts fixes the fault but costs $2,000 to $3,000 and leaves the same failure-prone design in place. Replacing the parts yourself saves the labor but still means several hundred dollars per part and, on a 4.7L, pulling the intake manifold. A bypass kit stops the system running and clears the codes permanently. Block-off plates on their own are not a fix.

Aftermarket pumps and valves are the route Hewitt warns against most: they fail in weeks or months, and an aftermarket pump that no longer makes pressure keeps setting codes even after a bypass kit is fitted. The block-off plates are part of the kit, not an alternative to it; without the module the ECM still runs and tests the system at every cold start and will keep reporting faults. For most owners the decision is which kit, not whether: Gen 1 for mechanical codes on 2005 to 2013 vehicles, Gen 2 for everything, including electrical codes, Flex Fuel, 2014 and newer, and reflashed trucks. See “Which kit fits my vehicle?” below.

What is a SAIS bypass kit, and how does it work?

A Hewitt SAIS bypass kit is a small electronic module and harness that stops the secondary air injection system from being run or, on the Gen 2, emulates a healthy system to the ECM, so the check engine light, limp mode and the SAIS codes go away and stay away. It plugs into the factory wiring, and the kit includes stainless block-off plates that seal the switching valves from the exhaust.

The Gen 1 kits (V36 and V54) prevent the system from operating at the cold-soak start, which clears the mechanical codes; the factory driver still monitors the electrical parts, so electrical codes need an add-on. The Gen 2 kits replace the air injection control drivers and emulate the whole system, so they clear mechanical and electrical codes, work with Flex Fuel and 2014 and newer vehicles that run the pumps at shutdown, and the SAIS readiness monitor shows complete after the first successful cycle. Nothing is removed from the engine unless you want to remove it. Hewitt designed and builds the kits in Lexington, South Carolina, assembles them by hand, and covers the modules with a limited lifetime warranty. They are sold for off-road, competition and emissions-exempt use only.

What do the block-off plates do, and do I need them?

The block-off plates are 316 stainless steel plates that bolt between each air switching valve and the exhaust, sealing the SAIS and its pressure sensors off from exhaust gas. If a valve is physically stuck open or leaking, they are required; in every other case they are strongly recommended, and they ship with every kit.

Without the plates, a valve that is fine today can start leaking later, send exhaust to the pressure sensor, and put the truck straight back into limp mode even though the system is bypassed. Installing them is the one step owners find fiddly, which is why the question comes up so often; the engine-specific plate instructions are on the instructions page and the plates are cut to fit each engine. If you decide not to install them right away, keep them in the glove box so they are there when you need them. Block-off plates product page.

Is there a Toyota recall or warranty extension for the secondary air injection system?

There is no safety recall. Toyota and Lexus have run warranty enhancement and service campaigns that covered SAIS parts on some models and years, but they were limited by time and mileage and most vehicles are now outside them.

Lexus ran Special Service Campaign JLG in 2019 covering air injection pumps and switching valves on 2010 to 2013 GX460s, and Toyota extended SAIS coverage on certain 2007 to 2013 Tundra and Sequoia V8s Toyota also issued a limited service campaign reflash for 2012 and 2013 5.7L Tundras and Sequoias setting P2441 and P2443 in freezing weather. The P2445 cold-weather reflash for 2005 and 2006 4.7L vehicles is no longer available. A dealer can check your VIN for any open campaign; if there is none, or your truck has aged out, a bypass kit is the economical route.

Legality and emissions

Is bypassing the SAIS legal, and will my truck pass emissions or inspection?

Federal and most state laws make it illegal to disable or render inoperative any emissions control device on a vehicle used on public roads, and the secondary air injection system is one. Hewitt bypass kits are sold for off-road, competition and emissions-exempt vehicles only; no other use is intended or implied, and it is the owner’s responsibility to know the rules where the vehicle is registered.

On the technical side: the SAIS is a supplementary system, and in many inspection programs its readiness monitor is not one of the monitors that must read complete. With a Gen 2 kit installed the SAIS monitor reports complete after the first successful emulated cycle; with a Gen 1 kit it may not. The kit does not touch the catalytic converters, oxygen sensors or evaporative system, and it has no effect on fuel trims, power or fuel economy, because the SAIS only ever ran for the first minute after a cold start. What it does remove is that cold-start function itself, which is why the kits are restricted to emissions-exempt use. Read the full disclaimer before ordering.

Fitment and products

Which kit fits my vehicle: Gen 1 (V36 or V54), Gen 2, or Gen 2 3-Valve?

The Gen 2 Plug & Play fits every 5.7L, 4.6L, 4.0L and 2.7L vehicle plus the 2007 to 2009 Tundra and 2008 to 2009 Sequoia 4.7L; the Gen 2 3-Valve fits every other 4.7L (2005 to 2006 Tundra, 2005 to 2007 Sequoia, all 4Runner V8, GX470, LX470, Land Cruiser). The Gen 1 V36 fits most 2005 to 2007 models and the Gen 1 V54H most 2008 to 2012 and select 2013 models, for mechanical codes only.

If you have any electrical code (P0412, P0415, P0416, P0417, P0418, P0419, P1613, P1614), a Flex Fuel 5.7L, a 2014 or newer vehicle, or a 2012 to 2013 5.7L that may have been reflashed, the Gen 2 is the kit. Use the Search by Vehicle tool for an exact match, or read the kit comparison. Product pages: Gen 2 Plug & Play, Gen 2 3-Valve, Gen 1 V36H, Gen 1 V36W, Gen 1 V54H.

Do I need the pressure sensor add-on (PSJ, PSR, PSRW, PSRH or PSO)?

You need a pressure sensor add-on only if a pressure sensor is damaged: that is, you have a pressure sensor circuit code (P2431 to P2438), the correlation code P106B, or a valve-stuck-open code that will not clear with the engine off or that comes back after the kit and block-off plates are installed. If your codes are purely mechanical and clear normally, the kit alone is enough.

Every solution still needs the ECM to see working pressure sensors; the add-ons replace a damaged sensor’s signal without replacing the expensive air switching valve it lives in. For Gen 1 kits: the Pressure Sensor Jumper (PSJ) is the cheapest, routing the good sensor’s signal in place of the damaged one on two-valve vehicles; the Pressure Sensor Replacement Harness (PSRH) and Replacement Double (PSRHD) add genuine Toyota sensors on a plug-and-play harness. For Gen 2 kits, the Gen 2 pressure sensor add-on (PSO) does the same job. For the 2005 to 2009 4.7L engines with a single sensor under the intake manifold, the Pressure Sensor Replacement Wired (PSRW) wires a new sensor in at the ECM so the manifold stays on. Hewitt uses only genuine Toyota sensors (part 89421-71010); aftermarket sensors cause problems. Not sure? Call with your codes and freeze-frame data and Hewitt will tell you before you order.

What are the Pump Proxy Pack and Valve Solenoid Pack add-ons for?

They are Gen 1 add-ons that let a Gen 1 kit clear the electrical codes it cannot clear on its own: the Pump Proxy Pack (PPP) for P0418 and P0419, and the Valve Solenoid Pack (VSP) for P0412 and P0415. Gen 2 kits do not need them, because the Gen 2 replaces the air injection drivers that monitor those circuits.

The Pump Proxy Pack plugs in at the air injection driver on the driver-side inner fender and stands in for a pump whose motor has failed, so the dead pump can stay in place instead of coming out from under a 4.7L intake manifold. One pack is needed per code. The Valve Solenoid Pack plugs in line at the driver connector and gives the driver what it reads as a healthy valve solenoid circuit, so the valve and its wiring do not have to be replaced or traced; again one per code. There is also a made-to-order Air Switching Valve Proxy that combines a solenoid pack with a pressure sensor replacement when both the solenoid and the sensor in one valve have failed. If you have several electrical codes, the Gen 2 kit is usually the simpler and cheaper answer.

Does the kit work with aftermarket intakes, headers, superchargers, tuners or remote starters?

Yes, with one exception. The Gen 2 kits connect only to the ECM and the pressure sensors, so they have no known compatibility issues with intakes, headers, superchargers, turbos, tuners or remote starters. The Gen 1 kits (V36 and V54) work with everything Hewitt has seen except inline “performance chips” that splice into the MAF/IAT sensor; those must be removed before a Gen 1 is installed.

Aftermarket intakes are fine with a Gen 1 as long as the MAF/IAT sensor sits in roughly the stock location; Hewitt can make a longer harness for a small upcharge if not. Headers are a common reason to fit a bypass kit even without an SAIS fault: headers with the air injection tube and flange are rare and expensive, so owners fit the kit and run headers without the air tube, sometimes with a spacer plate to block the air injection ports in the cylinder heads.

Can I remove the SAIS parts after the kit is installed?

With a Gen 2 kit, yes: you can remove everything except the air switching valves. With a Gen 1 kit, no, unless you add proxies for what you remove, because the factory driver keeps monitoring the pump and valve circuits.

The Gen 2 replaces the air injection drivers, so the pumps, hoses and driver modules can come out and nothing will miss them. The air switching valves have to stay on every kit because the pressure sensors the ECM still needs are built into them on 2007 and newer vehicles; if you want the valves gone too, fit external replacement sensors (the pressure sensor add-ons) in their place. Most owners leave everything in place, fit the block-off plates, and forget about it, which is also the cleanest way to keep the truck looking stock.

Install and post installation

How is the kit installed, how long does it take, and where are the instructions?

The kit plugs into the factory harness at the air injection driver on the inner fender and at the switching valve, intake air temperature and coolant temperature connectors, and the block-off plates bolt in at each switching valve; no splicing on the plug-and-play kits. Most owners finish a Gen 2 install in one to three hours with basic hand tools.

The sequence is: disconnect the battery, mount the module, connect the harness, fit the plates, reconnect, clear the codes and start the truck. The plates are the slowest step on most engines. The Gen 1 V36W wired kit is a six-wire hookup at the IAT/MAF harness for owners comfortable soldering; the V36H and V54H are plug-and-play plus one starter relay wire; the Gen 2 3-Valve for 4.7L engines has some wiring and Hewitt recommends professional installation. Illustrated, engine-specific PDF instructions for every kit, plate set and add-on are on the instructions page, and a printed copy ships with the kit.

Will the codes clear after I install the kit, and how do I reset the check engine light?

Yes. After the install, clear the codes with an OBD-II scanner or by disconnecting the negative battery terminal for about five minutes. Once cleared, the SAIS codes do not return because the system no longer runs (Gen 1) or completes every cycle (Gen 2).

Expect a rough idle or a brief stall on the first start after a battery disconnect; the ECM relearns its fuel trims within a few minutes of idling and driving. Any permanent codes still stored clear on their own at the next cold-soak start, when the Gen 2 completes the emulated cycle. C1201 clears with the SAIS codes. Two things can appear afterwards and both mean a damaged pressure sensor rather than a kit problem: a valve-stuck-open code that returns with the plates fitted, or P106B appearing for the first time, because its test only runs once the valve codes are gone. See “Do I need the pressure sensor add-on?” If you do not own a scanner, Hewitt sells iCarsoft OBD-II tools that read Toyota and Lexus codes.

Will a dealer ECM reflash or software update affect the kit?

A Gen 2 kit works on every vehicle regardless of any reflash. A Gen 1 V54H can be made incompatible by one specific update: Toyota’s limited service campaign for 2012 and 2013 5.7L Tundras and Sequoias that set P2441 or P2443 in freezing weather.

That campaign reflashed the ECM to run the air pumps at shutdown, like the Flex Fuel trucks, to purge moisture from the valves. A Gen 1 kit can only stop the system at start-up, so a reflashed truck will still run the system at shutdown and set codes. Reflashed vehicles are supposed to carry a Toyota modification sticker with the new calibration file under the hood, but the stickers are rarely applied. If there is any chance a 2012 or 2013 5.7L has had the update, buy the Gen 2 and avoid the question.

The kit is installed but a code is back. What do I check?

First note which code it is and whether it appeared after a cold-soak start, because the code tells you the cause. A valve-stuck-open code (P2440, P2442, P1441, P1444) with the block-off plates installed means a damaged pressure sensor and needs a pressure sensor add-on. P0418 or P0419 on a Gen 1 means the pump motor has failed electrically and needs a Pump Proxy Pack; P0412 or P0415 on a Gen 1 needs a Valve Solenoid Pack.

Other cases: P106B appearing for the first time after the install is the correlation test finally running, and again points at a sensor. P2445 on a 2005 or 2006 4.7L in freezing weather, set as you pass 50 mph, is the ECM glitch described under P2445 and is not the kit. P011B (intake and coolant temperature correlation) usually means a 2005 to 2007-spec Gen 1 module on a 2008 or newer vehicle; current V5 and later Gen 1 units avoid it. Aftermarket SAIS parts fitted before the kit can keep setting codes because they no longer produce the pressure the ECM expects. A code that cannot be cleared at all usually means the pressure sensor, driver, relay or wiring is damaged, not the pump. Call (844) 307-7671 with the vehicle, the codes and the freeze-frame data and Hewitt will tell you which it is.

Buying from Hewitt

Shipping, delivery time, returns and the warranty on the kit

Orders usually ship within one business day from Lexington, South Carolina, by USPS Priority Mail on free-shipping items or FedEx where selected, and Hewitt ships internationally. Bypass modules carry a limited lifetime warranty: if a module fails under normal use, Hewitt repairs or replaces it free for as long as the original buyer owns the vehicle.

The warranty is non-transferable and covers defects and failures under normal use; troubleshooting is done with Hewitt’s support team first, and the customer covers return shipping for inspection. Damage from improper installation, physical damage or alterations is not covered, and scan tools carry the manufacturer’s warranty, not Hewitt’s. Returns are accepted on new, unopened items in original packaging within 14 days of purchase with a Return Merchandise Authorization number, less a 15 percent restocking fee; scan tools are not returnable. Hewitt has no authorized third-party sellers, so a kit bought on another marketplace carries no Hewitt warranty or support. Full terms: policies and return policy.

Have a Question or Don’t Know What You Need?

Give us a Call Toll Free: 1-844-307-7671