Circuit Description
The engine control module (ECM) provides ignition voltage to the coil side of the fuel pump relay whenever the engine is cranking or running. The control module enables the fuel pump relay as long as the engine is cranking or running, and ignition system reference pulses are received. If no ignition system reference pulses are received, the control module turns OFF the fuel pump.
The fuel pump relay control circuit is equipped with a feedback circuit that is pulled up to 2.5 volts within the ECM. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage. If the ECM detects the control circuit voltage is more than a predetermined voltage when the circuit is commanded OFF, this DTC sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0629 Fuel Pump Relay Control Circuit High Voltage
Conditions for Running the DTC
| • | The engine speed is 0 RPM. |
| • | The ignition is ON, with the engine OFF. |
| • | The ignition 1 voltage is more than 10.5 volts. |
| • | The above conditions are met for more than 1 second. |
| • | DTC P0629 runs continuously once the above conditions are met. |
Conditions for Setting the DTC
| • | The ECM detects that the fuel pump relay control circuit is shorted to a voltage. |
| • | The condition exists for less than 4 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 4 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
| • | Use the J 35616-A/BT-8637 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector. |
| • | The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to Engine Controls Component Views . |
| • | If the condition is intermittent, move the related harnesses and connectors while monitoring the circuit status for the component in the Output Driver Module (ODM) data list with a scan tool. The circuit status parameter changes from OK to Fault if there is a condition with the circuit or a connection. |
| • | For an intermittent condition, refer to Intermittent Conditions . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step verifies that the control module is providing voltage to the fuel pump relay.
-
This step tests for an open in the ground circuit to the fuel pump relay.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 |
Important: Additional DTCs may set when using the Fuel Pump output control.
Does the fuel pump relay turn ON and OFF with each command? | Go to Step 3 | Go to Step 4 |
3 |
Did the DTC fail this ignition? | Go to Step 4 | Go to Diagnostic Aids |
Does the test lamp turn ON and OFF when commanded? | Go to Step 5 | Go to Step 6 | |
Does the test lamp turn ON and OFF when commanded? | Go to Step 7 | Go to Step 9 | |
6 | Test the control circuit of the fuel pump relay for a short to voltage or an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 12 | Go to Step 8 |
7 | Test for shorted terminals and for poor connections at the fuel pump relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 12 | Go to Step 10 |
8 | Test for shorted terminals and for poor connections at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 12 | Go to Step 11 |
9 | Repair the open ground circuit of the fuel pump relay. Refer to Wiring Repairs . Did you complete the repair? | Go to Step 12 | -- |
10 | Replace the fuel pump relay. Did you complete the replacement? | Go to Step 12 | -- |
11 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 12 | -- |
12 |
Did the DTC fail this ignition? | Go to Step 2 | Go to Step 13 |
13 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | System OK | |
