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
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests for voltage at the coil side of the AIR pump relay.
-
This step verifies that the PCM is providing ground to the AIR pump relay.
-
This step tests if a ground is constantly being applied to the AIR pump relay.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | |||
1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | |
2 | Are DTCs P0102, P0410, P0412, or P0443 set? | Go to Step 3 | Go to Step 4 |
3 |
Did you find and correct the condition? | Go to Step 18 | Go to Step 14 |
4 |
Does the AIR pump relay turn ON and OFF with each command? | Go to Step 5 | Go to Step 6 |
5 |
Did the DTC fail this ignition? | Go to Step 6 | Go to Intermittent Conditions |
Does the test lamp illuminate? | Go to Step 7 | Go to Step 13 | |
Does the test lamp turn ON and OFF when commanded with a scan tool? | Go to Step 11 | Go to Step 8 | |
Does the test lamp remain illuminated with each command? | Go to Step 10 | Go to Step 9 | |
9 |
Important: A short to voltage on the control circuit will allow the AIR pump to run continuously with the key in the OFF position. Test the AIR pump relay control circuit for an open or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 17 | Go to Step 12 |
10 |
Important: A short to ground on the control circuit will allow the AIR pump to run continuously with the ignition key in the ON position. Test the AIR pump relay control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 17 | Go to Step 16 |
11 | Test for an intermittent and for a poor connection at the AIR pump relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 18 | Go to Step 15 |
12 | Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 18 | Go to Step 16 |
13 | Repair the open or high resistance in the AIR pump relay ignition 1 voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 18 | -- |
14 | Repair the short to ground in the circuits that share the IGN 1 fuse or the shorted component on the same circuit. Did you complete the repair? | Go to Step 18 | -- |
15 | Replace the AIR pump relay. Did you complete the replacement? | Go to Step 18 | -- |
16 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | Go to Step 17 | -- |
17 |
Does the AIR pump turn ON when commanded with a scan tool? | Go to Step 18 | Go to Step 2 |
18 |
Did the DTC fail this ignition? | Go to Step 2 | Go to Step 19 |
19 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | System OK | |
