Gen 2: 3 Valve Secondary Air Injection System Bypass Kit (Partially Plug & Play)

(1 customer review)


The Gen 2 Bypass Kit is the most comprehensive unit and our recommended solution. It enables you to clear the Check Engine Light, Limp Mode and error codes related to both mechanical and electrical SAIS faults. Bypass kit will also include Block off Plate(s). Professional installation recommended.

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Hewitt Tech Generation 2 Secondary Air Injection System Bypass Kit (Plug & Play/Wired)*
The Hewitt Tech (HT) Gen 2 (3 Valve) Bypass Kit is for specific vehicles with 4.7L engines. On these vehicles the entire SIAS is located underneath the manifold. To make the Gen 2 Bypass kit compatible with this particular engine layout, HT had to develop the 3 Valve version. The functionality is the same but the installation of the Standard and 3 Valve version of the Gen 2 will vary. That said, the Gen 2 is still our most comprehensive bypass kit and for this reason is our recommended solution. It emulates the operation of the SAIS by replacing the Air Injection Drivers (AID). It enables you to clear the Check Engine Light, Limp Mode and error codes related to mechanical and electrical SAIS faults. Additionally, the SAIS system monitor will even show as complete/ready. The Gen 2 (3 Valve) is only compatible with specific Toyota and Lexus vehicles model years ’05 – ‘09. This includes vehicles that have had the ECM flashed with updated calibration file. The installation of the 3 Valve version of the Gen 2 Bypass is Plug & Play as well as Wired. The Plug & Play portion of the harness connects to the AID and Vacuum Switching Valve (VSV) factory harness. The Wired portion is ran through the fire wall and tapped into the factory harness at the ECM. The kit will come with tap connectors but we recommend soldering for best connectivity. The Gen 2 does include Block Off Plate(s) but will NOT need installation of the Starter Relay Wire. HT bypass kits are made with automotive grade materials and designed to blend in with the factory wiring harness. This allows for a very clean factory looking installation. Easy to follow step by step installation instructions are included with vehicle specific illustrations and wiring diagram. If you are not comfortable with soldering or tapping into the factory harness at the ECM, we recommend professional installation.

It is Important to understand that HT SAIS Bypass kits are engineered to work with Factory or OEM SAIS components. That said, aftermarket SAIS components can cause fault codes to be present after installation of the bypass kit. This typically means you will need HT Kit Addon(s) in order to clear SAIS codes that are still present.

The following are Trouble codes the Gen 2 Bypass Kit typically addresses**:

Mechanical Codes

P1441 – Switching Valve No.2 Stuck Open Bank 1
P1442 – Switching Valve No.2 Stuck Close Bank 1
P1444 – Switching Valve No.2 Stuck Open Bank 2
P1445 – Switching Valve No.2 Stuck Close Bank 2
P2440 – Switching Valve Stuck Open Bank 1
P2441 – Switching Valve Stuck Closed Bank 1
P2442 – Switching Valve Stuck Open Bank 2
P2443 – Switching Valve Stuck Closed Bank 2
P2445 – Pump Stuck OFF Bank 1***
P2447 – Pump Stuck Off Bank 2

Electrical Codes

P0412 – SAIS Switching Valve ‘A’ Circuit Malfunction Bank 1
P0415 – SAIS Switching Valve ‘B’ Circuit Malfunction Bank 2
P0418 – SAIS Circuit/Relay ‘A’ Circuit Malfunction Bank 1
P0419 – SAIS Circuit/Relay ‘B’ Circuit Malfunction Bank 2

The following are Trouble codes NOT addressed by the Gen 2 Bypass. These will require kit addon(s) in order to clear.

Pressure Sensor Codes

P2431 – Air Flow / Pressure Sensor Circuit Range / Performance Bank1
P2432 – Air Flow / Pressure Sensor Circuit Low Bank 1
P2433 – Air Flow / Pressure Sensor Circuit High Bank 1
P2436 – Air Flow / Pressure Sensor Circuit Range / Performance Bank 2
P2437 – Air Flow / Pressure Sensor Circuit Low Bank 2
P2438 – Air Flow / Pressure Sensor Circuit High Bank 2
P106B – Pressure Sensor Correlation / Evap. Pressure Sensor

These codes typically indicate a damaged Pressure Sensor which is usually caused by an Air Switching Valve being stuck open for an extended period of time. Functioning Pressure Sensors are needed for both Gen 1 and Gen 2 Bypass kits. Compatible Pressure Sensor addon required in order to clear.

GEN 2 Plug & Play (3 Valve) BYPASS KIT INCLUDES:

  • 1 x SAIS Bypass Module – Plug & Play Connections (AID)
  • 1 x SAIS Bypass Harness – Plug & Play Connections (ASV) Wired Connections (ECM)
  • 2 x Secondary Exhaust Valve Block Off Plates (Engine Specific)
  • Stainless Steel Mounting Hardware
    • 2 x Stainless Steel Screws
    • 2 x Stainless Steel 10 mm Hex Nuts
  • Installation Accessories
    • 2 x Plugs for Factory AID Wiring Harness
    • 3 x 3MTM Scotclok Tap Connectors (two Points of Contact)
    • 4 x ‘3 Inch Zip Ties
  • 1 x Printed Copy – Detailed Bypass Module Installation Instructions
  • 1 x Printed Copy – Block Off Plate Instructions (Engine Specific)


  • Bypass Module:
    • Custom Molded Black Duroplastic High Temp Enclosure – UL 94 V-0 Flame Resistance
    • Black Epoxy Potted for environmental and shock protection.
  • Bypass Wiring Harness:
    • Straight forward Plug & Play connections compatible with Factory components.
    • High Quality Automotive Engine Compartment Grade TXL Wiring
  • Block Off Plates:
    • 16 gauge (1/16 inch) 316 Stainless Steel Block Off Plate Construction for Lifetime Use
    • Water Jet Cut for Precision and Smoother Edges, Guaranteed to Fit Your Engine
  • Assembled 100% by hand in the USA!
  • Limited Life-Time Warranty


The Gen 2 Bypass kit is the best solution to address or prevent Secondary Air Injection issues. Unlike the Gen 1 Bypass kits which only manipulates the operation of the SAIS, the Gen 2 Bypass kit fully emulates it. Why is this an advantage? First, the Gen 2 can cover both Mechanical and Electrical SAIS fault codes. This limits the potential need of kit addons in the future. Second, the Gen 2 is compatible with Toyota’s most recent ECM flashes and recalibrations. This includes ECM programming for Flex Fuel models. Lastly, since the Gen 2 is emulating the SAIS system this means monitors will show as ready and complete even if the entire system is removed from the vehicle. The Gen 2 allows you remove the Air Pump(s), plumbing, Air Injection control drivers – and by adding Pressure Sensors Replacement Wired (PSRW), you can also remove the air switching valves.

When designing the Gen 2, it was critical the bypass seamlessly integrate with factory components and blend in under the hood. As a result, all connections for Gen 2 kit were engineered to be Plug & Play. This is another major advantage over the Gen 1 units because you do not have to worry about splicing into the factory harness or running a Starter Relay Wire to the fuse box. Additionally, HT had the protective enclosure costume molded to imitate the factory Air Injection Drivers. This allows you to mount directly to existing brackets. This in combination with the Plug & Play harness makes for a very professional and factory looking installation.

The included Air Switching Valve Block-off Plates are an integral part of the bypass kit. The Block Off Plates are the only way to isolate the Air Switching Valves and protect the related Pressure Sensor(s) from damage caused by exhaust. Open Air Switching Valves and Pressure Sensors exposed to exhaust are the primary cause of Limp Mode and SAIS failure.

It is important to understand that installing a HT bypass will prevent your Air Pumps and Air Switching Valves from operating. However, it will not close the Air Switching Valves or keep them closed in the future. That said, choosing not to install the Block Off Plates leaves the SAIS vulnerable because exhaust may leak into open valves and damage the Pressure Sensors. As noted above, both Gen 1 & 2 HT bypass kits require kit addons to clear SIAS Pressure Sensor codes. Do yourself a favor, avoid future frustrations and costs; install the Block Off Plates.

If you are having a hard time determining which is the best solution for your vehicle, please do not hesitate to give us a call or send an email. Hewitt is here to help!


*Professional installation is recommended. Gen 2 (3 Valve) kit installation requires tapping directly into the factory harness at the ECM.  For best connectivity, soldering wire connections is recommended.

**The vehicles fuses, Pressure Senor(s), factory wiring harness and Engine Control Module (ECM) must be in good working condition for bypass kit to operate properly.

***There is a known “Cold Weather Glitch” on some older 4.7L engines. If the vehicle is tripping a P2445 and it is caused by this glitch; the Hewitt Technologies SAIS Bypass Kit will not resolve the issues. Please visit our Error Codes page or give us a call to learn more.


It is illegal to remove, dismantle or otherwise cause to be inoperative any pollution control device required by federal, state, or local emissions law. Our bypass kits are sold for off-road, competition or other emissions exempt vehicles only. No other applications are intended or implied. By installing or using this SAIS Bypass Kit the vehicle owner and installer acknowledge and assumes ALL risks associated with its use.

Additional information

Weight 1 lbs
Dimensions 8 × 7 × 2 in

2005, 2006, 2007, 2008, 2009, 2010, 2011


Lexus, Toyota


Tundra, Sequoia, 4Runner, Land Cruiser, GX 470, LX 470



1 review for Gen 2: 3 Valve Secondary Air Injection System Bypass Kit (Partially Plug & Play)

  1. Gail Fitzgerald

    After a lot of research & info from Hewitt Tech, I purchased the Gen II. After install, the troublesome issue was resolved and the truck is back on the road, registered & compliant.

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