What it means
The ECU detects a general fault in the secondary air injection system air flow or pressure sensor circuit. The diagnostic cannot verify proper SAI operation.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The SAI system sends air into the exhaust during certain operating conditions, and its bank 1 air-flow or pressure sensor reports whether the air is moving as expected. P2431 sets when the signal is within an electrical range but does not match the system's expected response, so the control module cannot confirm proper SAI operation.
Common causes
Most likely first.
- Defective SAI sensor
- SAI sensor wiring fault
Symptoms
- Check-engine light on
- Rough cold start
- Reduced power or increased emissions
How to diagnose it
- Use freeze-frame data and live sensor readings to compare bank 1 SAI pressure or flow before and during a commanded pump operation.
- Inspect the bank 1 sensor connector and harness for damage, corrosion, loose pins, or poor contact that could skew an otherwise plausible signal.
- Check the SAI hoses, passages, and check valve on bank 1 for leaks, restriction, or sticking that could make sensor response differ from expectation.
- Test the sensor signal and circuit continuity while commanding the pump, comparing results with the manufacturer's specification.
- If the air path and wiring are sound, assess the bank 1 sensor for drift or failure and replace it only if confirmed.
Common fixes
- Repair a leaking or restricted bank 1 SAI hose or passage.
- Restore a loose, corroded, or damaged sensor connector or harness.
- Replace a sticking SAI check valve or other confirmed air-path fault.
- Replace the bank 1 air-flow or pressure sensor if its response is outside specification.
Can I keep driving?
If the engine runs normally, limited driving is generally possible, but the fault can increase emissions and cause rough cold starts. Avoid delaying repair if the vehicle loses power or runs poorly.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.