P0629

DTC P0627-P0629

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.

DTC Descriptors
DTC P0627
- Fuel Pump Relay Control Circuit Open

DTC P0628
- Fuel Pump Relay Control Circuit Low Voltage

DTC P0629
- Fuel Pump Relay Control Circuit High Voltage

Diagnostic Fault Information





Circuit/System 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 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.

Conditions for Running the DTC

P0627 and P0629
* The engine speed is greater than 80 RPM.
* The ignition voltage is between 10-18.1 V.
* The ECM has commanded the fuel pump relay OFF.
* The above conditions are met for greater than 1 second.
* The DTCs run continuously once the above conditions are met.

P0628
* The engine speed is greater than 80 RPM.
* The ignition voltage is between 10-18.1 V.
* The ECM has commanded the fuel pump relay ON.
* The above conditions are met for greater than 1 second.
* The DTC runs continuously once the above conditions are met.

Conditions for Setting the DTC

P0627

The ECM detects the fuel pump relay control circuit is open.

P0628

The ECM detects the fuel pump relay control circuit is shorted to ground.

P0629

The ECM detects the fuel pump relay control circuit is shorted to voltage.

The DTCs set when the above conditions are met for more than 4 seconds or a cumulative of 50 seconds.

Action Taken When the DTC Sets

DTCs P0627, P0628, and P0629 are Type B DTCs.

Conditions for Clearing the DTC

DTCs P0627, P0628, and P0629 are Type B DTCs.

Reference Information
Schematic Reference

Engine Controls Schematics ([1][2]Electrical Diagrams)
Connector End View Reference

* Component Connector End Views (Connector Views)
* Electrical Center Identification Views (Application and ID)

Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information
Special Tools

J 43244 - Relay Puller Pliers

Circuit/System Verification

1. Ignition ON, command the fuel pump relay ON and OFF with a scan tool. Listen/feel for relay to click and for fuel pump to turn ON and OFF.
2. Attempt to start the engine. Observe the DTC information with a scan tool. DTC P0627, P0628, or P0629 should not set.
3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

1. Ignition OFF, disconnect the fuel pump relay using the J 43244 - Pliers.
2. Connect a test lamp between the control circuit terminal 86 of the fuel pump relay and ground.
3. Ignition ON, command the fuel pump relay ON and OFF with a scan tool. The test lamp should turn ON and OFF as commanded.

• If the test lamp remains OFF all the time, test for a short to ground or an open/high resistance on the control circuit. If the circuit/connections test normal, replace the ECM.
• If the test lamp remains ON all the time, test for a short to voltage on the control circuit. If the circuit/connections test normal, replace the ECM.

4. Ignition OFF, connect a test lamp between the fuel pump relay control circuit terminal 86 and the ground circuit terminal 85 of the fuel pump relay.
5. Ignition ON, command the fuel pump relay ON and OFF with a scan tool. The test lamp should turn ON and OFF as commanded.

• If the test lamp does not turn ON when commanded, repair the open/high resistance in the ground circuit of the fuel pump relay.

6. Ignition ON, test for 2-3 V on the control circuit terminal 86 of the fuel pump relay.

• If not within the specified range, replace the ECM.

7. If all circuits/connections test normal, test or replace the fuel pump relay.

Component Testing

1. Ignition OFF, disconnect the fuel pump relay.
2. Test for 135-185 ohm between terminals 85 and 86.

• If the resistance is not within the specified range, replace the relay.

3. Test for infinite resistance between the following terminals:

* 30 and 86
* 30 and 87
* 30 and 85
* 85 and 87

• If not the specified value, replace the relay.

4. Install a 15 A fused jumper wire between relay terminal 85 and 12 V. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohm between terminals 30 and 87.

• If greater than the specified range, replace the relay.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Control Module References (Programming and Relearning) for ECM replacement, setup, and programming