P0418

DTC P0418

CIRCUIT DESCRIPTION
The secondary air injection (AIR) pump relay controls the high current flow to the AIR pump. Ignition voltage is supplied to the AIR pump relay coil when the ignition is ON. Battery positive voltage is supplied to the armature contacts at all times. The powertrain control module (PCM) controls the relay by supplying a ground path to the relay coil control circuit by an internal integrated circuit called an output driver module (ODM). The low side driver also incorporates a fault detection circuit that is continuously monitored by the PCM. The voltage on the control circuit should be battery voltage when the ignition is ON and the AIR pump relay is at rest. If the fault detection circuit measures a low voltage under this condition it is an indication of an open or short to ground on the control or ignition 1 circuits. An open AIR pump relay coil fault may also be present. If the PCM detects low voltage on the AIR pump relay control circuit when the AIR pump relay is commanded OFF or a high voltage when the AIR pump relay is commanded ON, DTC P0418 sets.

CONDITIONS FOR RUNNING THE DTC
- The engine speed is more than 400 RPM.
- The system voltage is between 6-18 volts.

CONDITIONS FOR SETTING THE DTC
- The PCM detects that the commanded state of the driver and the actual state of the control circuit do not match.
- All the above conditions exist for a minimum of 5 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.





DIAGNOSTIC AIDS

TEST DESCRIPTION

Steps 1-10:

Steps 11-19:

The numbers below refer to the step numbers on the diagnostic table.
5. This step tests for voltage at the coil side of the relay.
6. 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.