System Description
The secondary air injection (AIR) system aids in the reduction of hydrocarbon emissions during a cold start. The system forces fresh filtered air into the exhaust stream in order to accelerate the catalyst operation. An electric air pump, the AIR pump, provides filtered air on demand to the AIR control solenoid valve/pressure sensor assembly. The AIR control solenoid valve/pressure sensor assembly controls the flow of air from the AIR pump to the exhaust manifold. The AIR valve relay supplies the current needed to operate the AIR control solenoid valve/pressure sensor assembly. A pressure sensor is used to monitor the air flow from the AIR pump. The powertrain control module (PCM) supplies the internal pressure sensor with a 5-volt reference, an electrical ground and a signal circuit.
The AIR diagnostic uses 3 phases to test the AIR system:
- DTCs P0411 and P2430 run during Phase 1
- DTCs P2430 and P2440 run during Phase 2
- DTC P2444 runs during Phase 3
In all 3 phases, testing is accomplished by comparing the measured pressure against the expected pressure. The PCM detects faults in the AIR pump, AIR control solenoid valve/pressure sensor assembly and the exhaust check valve. The pressure sensor is also used to detect leaks and restrictions in the secondary AIR system plumbing.
DTC P2440-The AIR control/shut-off valve stuck open diagnostic monitors system airflow. This diagnostic test detects insufficient system pressure due to a malfunctioning AIR control solenoid valve/pressure sensor assembly or AIR valve relay, a malfunctioning AIR pump relay or a restricted or leaking system. When the PCM detects AIR system pressure is too low, DTC P2440 sets. DTC P2440 runs during Phase 2.
- Phase 2
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The PCM commands the AIR pump ON and the AIR control/shut-off valve closed.
- The AIR system pressure is sufficient and DTC P2440 passes. DTC P2440 AIR diagnostic proceeds to Phase 3.
- The AIR system pressure is not sufficient. DTC P2440 AIR diagnostic fails, testing is stopped and DTC P2440 sets.