System Description

WARNING: This page is about a different car, the 2004 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.

The DTC P2431 Secondary Air Injection (AIR) System Pressure Sensor Performance diagnostic monitors the accuracy of the sensor signal. The secondary AIR system helps reduce exhaust emissions. The system forces fresh filtered air into the exhaust stream in order to accelerate the catalyst operation. An electric air pump, the secondary AIR injection pump, provides filtered air on demand to the AIR shut off valve. The AIR shut off valve controls the flow of air from the AIR pump to the exhaust manifold. The AIR solenoid valve supplies the manifold vacuum that is used to operate the AIR shut off valve. A pressure sensor is used to monitor the air flow from the AIR pump. The PCM supplies the pressure sensor with a 5-volt reference, an electrical ground, and a signal return circuit that has a 5-volt bias. By comparing the measured pressure against the expected pressure the pressure sensor can detect faults in the AIR pump, AIR shut off valve, and the AIR solenoid valve. The pressure sensor can also detect leaks in the secondary AIR system plumbing.