Cause
Faulty secondary air switching valve
The valve deciding when pumped air reaches the exhaust. Stuck open, it feeds air past the oxygen sensors continuously — they cannot tell that oxygen from oxygen that survived combustion, so they report a lean mixture that does not exist and the module over-fuels until the engine genuinely runs rich. A vacuum leak hunt finds nothing, because the unmetered air is in the exhaust.
Typically a moderate job.
Codes this can cause (18)
Codes where this is a likely explanation first, rather than merely a possible one.
- P0412 Secondary Air Injection System Switching Valve A Circuit Malfunction Likely for this code Low
- P0415 Secondary Air Injection System Switching Valve B Circuit Malfunction Likely for this code Low
- P2259 Secondary Air Injection System Control B Circuit Low Likely for this code Moderate
- P2260 Secondary Air Injection System Control B Circuit High Likely for this code Moderate
- P2440 Secondary Air Injection System Switching Valve Stuck Open Bank 1 Likely for this code High
- P2441 Secondary Air Injection System Switching Valve Stuck Closed Bank 1 Likely for this code Moderate
- P2442 Secondary Air Injection System Switching Valve Stuck Open Bank 2 Likely for this code High
- P2443 Secondary Air Injection System Switching Valve Stuck Closed Bank 2 Likely for this code Moderate
- P2448 Secondary Air Injection System High Air Flow Bank 1 Likely for this code Moderate
- P2449 Secondary Air Injection System High Air Flow Bank 2 Likely for this code Moderate
- P0410 Secondary Air Injection System A Moderate
- P0411 Secondary Air Injection System A Incorrect Flow Detected Moderate
- P0491 Secondary Air Injection System Insufficient Flow — Bank 1 Low
- P0492 Secondary Air Injection System Insufficient Flow — Bank 2 Low
- P2431 Secondary Air Injection System Air Flow Pressure Sensor Circuit Range/Performance Bank 1 Moderate
- P2436 Secondary Air Injection System Air Flow Pressure Sensor Circuit Range/Performance Bank 2 Moderate
- P2444 Secondary Air Injection System Pump Stuck On Bank 1 High
- P2446 Secondary Air Injection System Pump Stuck On Bank 2 High
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