GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Daewoo 🢒 2009 🢒 W200 🢒 DTC 🢒 DTC P0627, P0628, or P0629

DTC P0627, P0628, or P0629 W/LY7

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 Descriptors

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 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.

Conditions for Running the DTC
    • The engine speed is greater than 80 RPM.
    • The ignition voltage is 10-18 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 less than 1 second.
    • The DTCs runs continuously once the above conditions are met.

Conditions for Setting the DTC

P0627

The ECM detects the voltage on the fuel pump relay control circuit is within a predetermined range when the control circuit is commanded OFF. The condition exists for greater than 4 seconds, or a cumulative time of 30 seconds.

P0628

The ECM detects the fuel pump relay control circuit voltage is less than 2.21 volts when the control circuit is commanded ON. The condition exists for greater than 4 seconds, or a cumulative time of 30 seconds.

P0629

The ECM detects the fuel pump relay control circuit voltage is greater than 2.21 volts when the control circuit is commanded OFF. The condition exists for greater than 4 seconds, or a cumulative time of 30 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

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
  1. Ignition ON, command the Fuel Pump Relay ON and OFF with a scan tool. You should hear an audible click.
  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.
  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 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. 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 ON and OFF with a scan tool. The test lamp should turn ON and OFF as commanded.
    6. ⇒If the test lamp does not turn ON when commanded, repair the open/high resistance in ground circuit of the fuel pump relay.
  6. If all circuits/connections test normal, test or replace the fuel pump relay.

Component Testing
  1. Test for 135-185 Ω between terminals 85 and 86 of the fuel pump relay.
    2. ⇒If not within the specified range, replace the fuel pump relay.
  2. Test 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 20 A fused jumper 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. Test for less than 2 Ω between terminals 30 and 87 of the relay.
    4. ⇒If greater than the specified range, replace the fuel pump relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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

DTC P0627, P0628, or P0629 w/LLT

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 Descriptors

DTC P0627: Fuel Pump Control Circuit

DTC P0628: Fuel Pump Control Circuit Low Voltage

DTC P0629: Fuel Pump Control Circuit High Voltage

Circuit/System Description

The engine control module (ECM) supplies voltage to the fuel pump flow control module (FPCM) when the ECM detects that the ignition is on. The voltage from the ECM to the FPCM remains active for 2 seconds, unless the engine is in crank or run. While this voltage is being received, the FPCM supplies a varying voltage to the fuel tank pump module in order to maintain the desired fuel rail pressure.

Conditions for Running the DTC
    • The engine speed is greater than 80 RPM.
    • The ignition voltage is 10-18 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 less than 1 second.
    • The DTCs runs continuously once the above conditions are met.

Conditions for Setting the DTC

P0627

The ECM detects the voltage on the fuel pump control enable circuit is within a predetermined range when the control circuit is commanded OFF. The condition exists for greater than 4 seconds, or a cumulative time of 30 seconds.

P0628

The ECM detects the fuel pump control enable circuit voltage is less than 2.21 volts when the control circuit is commanded ON. The condition exists for greater than 4 seconds, or a cumulative time of 30 seconds.

P0629

The ECM detects the fuel pump control enable circuit voltage is greater than 2.21 volts when the control circuit is commanded OFF. The condition exists for greater than 4 seconds, or a cumulative time of 30 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.

Diagnostic Aids

Using the Failure Records data may help locate an intermittent condition. If you cannot duplicate the DTC, the information in the Failure Records can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can help determine how many ignition cycles that the diagnostic test reported a pass and/or a fail.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Fuel System Description

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, observe the DTC information with a scan tool. DTC P069E should not be set.

⇒If the DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis of FPCM DTCs.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.