Circuit Description
The secondary air injection (AIR) pump relay controls the high current flow to the AIR pump. this allows the powertrain control module (PCM) driver to control only the low current that is used by the relay coil. Ignition 1 voltage is directly supplied to the AIR pump relay coil. The PCM controls the relay by supplying a ground to the control circuit of the AIR pump relay. When the PCM commands the relay ON, the voltage of the control circuit should be low, near 0 volts. When the PCM commands the relay OFF, the voltage potential of the circuit should be high, near the battery voltage. If the PCM monitor detects a voltage other than expected, 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. |
| • | The above condition exists 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
AIR Pump Relay Terminal Identification | |||
|---|---|---|---|
Front of Vehicle | |||
Left Side of Vehicle | Ignition | B+ | Right Side of Vehicle |
Pump Supply | Control | ||
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 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, P0412, P0443, P0449, P0740, P0785, P1860 also set? | Go to Step 13 | Go to Step 3 |
3 |
Does the AIR pump relay turn ON and OFF with each command? | Go to Step 4 | Go to Step 5 |
4 |
Does the DTC fail this ignition? | Go to Step 5 | Go to Intermittent Conditions |
Does the test lamp illuminate? | Go to Step 6 | Go to Step 12 | |
Does the test lamp turn ON and OFF? | Go to Step 10 | Go to Step 7 | |
Does the test lamp remain illuminated when the scan tool was commanded ON and OFF? | Go to Step 9 | Go to Step 8 | |
8 |
Important: The AIR pump may be damaged if the control circuit is shorted to voltage. Test the AIR pump relay control circuit for a short to voltage or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 11 |
9 |
Important: The AIR pump may be damaged if the control circuit is shorted to ground. 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 14 | Go to Step 17 |
10 | Test for an intermittent and for a poor connection at the AIR pump relay connector. 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 |
11 | 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 17 |
12 | Repair the open circuit in the ignition 1 voltage circuit of the AIR pump relay. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 18 | -- |
13 |
Did you complete the repair? | Go to Step 18 | -- |
14 |
Does the AIR pump turn ON and OFF when commanded with a scan tool? | Go to Step 18 | -- |
15 |
Did you complete the replacement? | Go to Step 18 | -- |
16 | Replace the AIR relay. Did you complete the replacement? | Go to Step 18 | -- |
17 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | Go to Step 18 | -- |
18 |
Important: The scan tool status for this DTC will not report a pass. The scan tool will only display if the diagnostic test fails. The repair is not complete if the scan tool indicates that the diagnostic test ran and failed.
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 | |
