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DTC P0628 or P0629 (LLU)

DTC P0628 or P0629 (LLU)

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 P0628 00

Fuel Pump Relay Control Circuit Low Voltage

DTC P0629 00

Fuel Pump Relay Control Circuit High Voltage

Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performance
Control Circuit

P0628 00

-

P0629 00

-

Ground

-

-

-

-



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's relay control circuit is equipped with a feedback circuit that receives voltage within the ECM. By monitoring the voltage in the feedback circuit the ECM can determine whether the control circuit is open, short-circuited to ground or short-circuited to a voltage.

Conditions for Running the DTC


• The ignition is ON or the engine is running.

• The ignition voltage is between 11-18 V.

• These DTCs run continuously once the above conditions are met.


Conditions for Setting the DTC

P0628 00

The ECM detects the fuel pump relay control circuit is shorted to ground for greater than 1 s.

P0689 00

The ECM detects the fuel pump relay control circuit is shorted to voltage for greater than 1 s.

Action Taken When the DTC Sets


• DTCs P0628 00, and P0629 00 are Type D DTCs.

• Depending on the condition, the engine may not start.


Conditions for Clearing the DTC

DTCs P0628 00, and P0629 00 are Type D 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

Note

If you were sent here from engine cranks but does not run proceed to Circuit/System Testing.



1. Ignition ON, command the Fuel Pump Relay ON and OFF with a scan tool. You should hear and feel an audible click with the KR23A Fuel Pump Relay.

2. Ignition ON, check the diagnostic trouble code (DTC) information with a scan tool. DTC P0628 00 or P0629 00 should not be 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, remove the KR23A Fuel Pump Relay, from the underhood fuse block.

2. Test for less than 5 Ω between the ground circuit terminal 86 and ground

3. If greater than the specified range, test the ground circuit for an open/high resistance

4. Connect a test lamp between the control circuit terminal 85 and ground.

5. Ignition ON, command the Fuel Pump Relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

6. If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module.

7. If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.

8. If all circuits test normal, test or replace the KR23A Fuel Pump Relay.


Component Testing


Relay Test

1. Ignition OFF, disconnect the KR23A Fuel Pump Relay.

2. Measure for 70-110 Ω between terminals 85 and 86 of the KR23A Fuel Pump Relay.

3. If the resistance is not within the specified range, replace the KR23A Fuel Pump Relay.

4. Measure for infinite resistance between following terminals of the KR23A Fuel Pump Relay:

• Terminals 30 and 86

• Terminals 30 and 87

• Terminals 30 and 85

• Terminals 85 and 87

• If continuity is detected, replace the KR23A Fuel Pump Relay.

5. Connect a 20 A fused jumper wire from the positive terminal of the battery to KR23A Fuel Pump Relay terminal 85. Connect a jumper wire from the negative terminal of the battery to KR23A Fuel Pump Relay terminal 86. Measure for less than 5 Ω between KR23A Fuel Pump Relay terminal 30 and KR23A Fuel Pump Relay socket terminal 87.

6. If the resistance measures more than 5 Ω, replace the KR23A Fuel Pump Relay.


Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.


• Relay Replacement (Attached to Wire Harness)

• Control Module References for Engine Control Module replacement, setup, and programming