P0418

CIRCUIT DESCRIPTION
The powertrain control module (PCM) commands the AIR pump relay ON by supplying a ground to the control circuit of the AIR pump relay. The AIR pump relay supplies high current to the AIR pump supply voltage circuit. Voltage is supplied to the AIR pump relay though the ignition 1 voltage circuit, protected by a fuse. When the PCM commands the AIR pump relay ON, the voltage on the control circuit should be low or near 0 volts. When the PCM commands the AIR pump relay OFF, the voltage potential of the circuit should be high, near battery voltage. The PCM monitors the voltage and supplies the ground to the relay by means of an internal driver. If the PCM detects a voltage other than what is expected, DTC P0418 sets.

CONDITIONS FOR RUNNING THE DTC
- The engine is running.
- The system voltage is between 8-16 volts.

CONDITIONS FOR SETTING THE DTC
- The PCM detects an improper voltage level on the output circuit that controls the AIR pump relay.
- The condition exists for at least 10 seconds.

ACTION TAKEN WHEN THE DTC SETS
- The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
- The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
- The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
- Clear the MIL and the DTC with a scan tool.

TEST DESCRIPTION

Steps 1-6:

Steps 7-11:

Steps 12-17:

Steps 18-19:

The numbers below refer to the step numbers on the diagnostic table.
6. This step tests for voltage at the coil side of the AIR pump relay.
7. This step verifies that the PCM is providing ground to the AIR pump relay.
8. This step tests if a ground is constantly being applied to the AIR pump relay.