GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Holden 🢒 2008 🢒 WM Sedan 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC P0627, P0628, or P0629

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

DTC Descriptor

DTC P0627: Fuel Pump Relay Control Circuit

DTC P0628: Fuel Pump Relay Control Circuit Low Voltage

DTC P0629: Fuel Pump Relay Control Circuit High Voltage

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Battery Voltage - Relay Switch

1

2

--

--

Fuel Pump Supply Voltage

1

2

3

--

Fuel Pump Relay Control

P0628

P0627

P0629

--

Fuel Pump Ground

--

P0627

--

--

  1. The fuel pump fuse opens and the engine cranks but does not run.
  2. The engine cranks but does not run.
  3. The fuel pump operates continuously and the battery will discharge.

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 ECM 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 ECM 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.

Conditions for Running the DTC
    • The ignition is ON, with the engine OFF.
    • The ignition voltage is greater than 10.5  volts.
    • The ECM has commanded the fuel pump relay ON and OFF at least once during the ignition cycle.
    • The above conditions are met for more than 1 second.
    • The DTCs runs continuously once the above conditions are met.

Conditions for Setting the DTC

DTC P0627

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

DTC P0628

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

DTC P0629

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

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

Connector End View Reference

Component Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, command the Fuel Pump Relay ON and OFF with a scan tool. You should hear an audible click.

Circuit/System Testing
  1. Ignition OFF, disconnect the fuel pump relay.
  2. Connect a test lamp between the control circuit of the fuel pump relay and a known ground.
  3. Ignition ON, command the fuel pump ON and OFF with a scan tool. The test lamp should turn ON and OFF as commanded.
    4. ⇒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 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 circuit/connections test normal, replace the ECM.
  4. If all circuits/connections test normal, test or replace the fuel pump relay.

Component Testing
  1. Measure for 70-110 ohms of resistance between terminals 85 and 86 of the fuel pump relay.
    2. ⇒If the resistance is not within the specified range, replace the fuel pump relay.
  2. Measure for infinite resistance between the following terminals of the fuel pump relay:
    3. • 30 and 86
    • 30 and 87
    • 30 and 85
    • 85 and 87
    ⇒If continuity is detected, replace the fuel pump relay.
  3. Connect a 5-A fusible link wire from the positive terminal of the battery to relay terminal 85. Connect a jumper wire from the negative terminal of the battery to relay terminal 86. Measure for less than 2 ohms between terminals 30 and 87 of the relay.
    4. ⇒If the resistance measures more than 2 ohms, replace the fuel pump relay.

Repair Instructions

Perform the Diagnostic Repair Verification.

    •  Relay Replacement
    •  Engine Control Module Replacement for engine control module replacement, setup and programming.