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Check Engine Light for Secondary Air Injection System on 2021 GX 460

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James R. · rep 0 · May 22, 4:42 AM · 1 replies · solved · Question

Vehicle: 2021 Lexus GX 460 Premium

Hello fellow Lexus owners,

I'm experiencing an issue with my 2021 Lexus GX 460 Premium. The check engine light recently illuminated, and when I scanned it, I got codes P0418 and P0419, which point to the secondary air injection system. Specifically, P0418 is for the 'Secondary Air Injection System Relay 'A' Circuit' and P0419 for 'Secondary Air Injection System Relay 'B' Circuit'.

The car seems to be driving fine, with no noticeable performance issues or strange noises, but the light is definitely on. I've read that this system is mainly for emissions during cold starts. Is this a common problem for the GX 460, especially the newer models?

What's typically involved in fixing this? I'm hoping it's just a relay or a fuse, but I'm prepared for something more involved if necessary. Any advice from those who've dealt with this would be great!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:42 AM

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Hi John,

Codes P0418 and P0419 on your 2021 Lexus GX 460 indicate a problem with the secondary air injection (SAI) system, specifically related to the control circuits for the air pump relays. This is a relatively common issue on many Toyota/Lexus trucks and SUVs.

Common Causes:

  1. Failed Air Pump: The electric air pump itself, which injects air into the exhaust during cold starts to help warm up the catalytic converters faster, can fail. This is often due to moisture ingress or motor wear.
  2. Stuck Air Switching Valves: The SAI system uses a pair of valves (often called 'switching valves' or 'check valves') that direct the airflow. These valves can become stuck open or closed due to carbon buildup or internal failure, leading to incorrect pressure readings or airflow.
  3. Faulty Relays: Since your codes specifically mention relay circuits (P0418, P0419), the relays that power the air pump are prime suspects. These can fail electrically.
  4. Wiring Issues: Less common, but damaged or corroded wiring to the air pump or relays can also cause these codes.
  5. Carbon Buildup: In some cases, excessive carbon buildup in the exhaust ports where the SAI system injects air can restrict flow and trigger codes, though this is more common with valve-related codes (P0410, P0412).

When to See a Shop:

  1. Diagnosis is Key: While the car might drive fine, the check engine light means your vehicle isn't passing emissions. A professional diagnosis is crucial to determine if it's the pump, valves, relays, or wiring. They can test the components individually.
  2. Specialized Tools: Accessing and testing the SAI components, especially the valves, often requires specific tools and knowledge of the system's operation.
  3. Emissions Compliance: If you live in an area with emissions testing, this issue will prevent your vehicle from passing. It's best to address it before your next inspection is due.
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