P0418

DTC P0418

CIRCUIT DESCRIPTION
The secondary air injection (AIR) pump relay controls high current to the AIR pump. The AIR pump relay armature is held in the open position by spring tension. 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) supplies the ground path to the relay coil control circuit by an internal integrated circuit called an output driver module (ODM). One of the ODM output circuits is configured to operate as a low side driver for the AIR pump relay. 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 a short to ground on the control or the 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, diagnostic trouble code (DTC) P0418 will set.

DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC P0418 Secondary Air Injection (AIR) Pump Control Circuit

CONDITIONS FOR RUNNING THE DTC
- The engine is running.
- The system voltage is between 8-16 volts.
- This DTC runs on a 100 ms loop. DTC P0418 runs continuously once the above conditions are met.

CONDITIONS FOR SETTING THE DTC
- The PCM detects a low voltage on the AIR pump relay control circuit with the key ON and the AIR pump relay commanded OFF.
- The condition exists for at least 15 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 (MI L) 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 1-8:

Steps 9-18:

The numbers below refer to the step numbers on the diagnostic table.
7. This step verifies that the PCM is providing ground to the AIR pump relay when the command is ON.
8. This step tests if a ground is constantly being applied to the AIR pump relay control circuit.
9. This step tests for a short to voltage on the AIR pump relay control circuit. This will allow the AIR pump to run continually with the key in the OFF position.
10. This step tests for a short to ground on the AIR pump relay control circuit. This will allow the AIR pump to operate continually with the key in the ON position.