Secondary Air Injection System Air Flow/Pressure Sensor Circuit Range/Performance Bank 1
The Powertrain Control Module (PCM) detected that the signal from the Secondary Air Injection (SAI) system air flow or pressure sensor for Bank 1 is out of the expected range or performing poorly. This indicates the sensor is providing erratic or implausible readings compared to the commanded state of the SAI pump and valves.
This code primarily affects the vehicle's emissions control system and will cause an emissions test failure. It is generally safe to drive with this code in the short term, but it should be repaired to ensure proper emissions compliance.
Common symptoms
- Illuminated Check Engine Light (MIL)
- Failed state emissions test
- Increased tailpipe emissions during cold starts
- Possible slight hesitation on cold engine start
- Unusual noise from the secondary air injection pump if a physical leak is present
Likely causes
- Defective secondary air injection pressure/flow sensor
- Damaged, corroded, or loose wiring and connectors in the sensor circuit
- Vacuum leaks or damaged hoses in the secondary air injection system
- Faulty secondary air injection pump or check valve
- Carbon buildup restricting the secondary air injection ports
- Faulty Powertrain Control Module (PCM) (rare)
What to check before replacing parts
Visually inspect the secondary air injection system hoses and sensor wiring.
Look for: Look for cracked, disconnected, or brittle vacuum/air hoses, as well as frayed wires or corroded connectors at the pressure sensor.
Monitor the SAI pressure sensor data using a scan tool.
Look for: Look for the sensor voltage or pressure reading to fluctuate erratically or remain fixed when the SAI pump is commanded on and off.
Test the SAI pressure sensor circuit with a multimeter.
Look for: Verify the presence of a 5-volt reference signal and a good ground at the sensor connector; lack of either indicates a wiring or PCM issue.
Test the operation of the secondary air injection pump and check valve.
Look for: Ensure the pump generates strong airflow when commanded on and that the check valve opens properly without allowing exhaust gas to flow backward into the pump.
Inspect the secondary air injection ports for carbon buildup.
Look for: Look for clogged passages in the exhaust manifold or cylinder head that would restrict airflow, causing abnormal pressure readings at the sensor.
This page explains the generic P2431 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
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