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 CircuitDTC 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 |
|---|---|---|---|
Fuel Pump Relay Control | P0628 | P0627 | P0629 |
Circuit/System Description
The engine control module (ECM) supplies voltage to the fuel pump control module when the ECM detects that the ignition is ON. The voltage signal from the ECM to the FPCM remains active for 2 seconds, unless the engine is in Crank or Run. While this signal is being received, the FPCM closes the ground switch of the fuel pump and also supplies a varying voltage to the fuel pump module in order to maintain the desired fuel pressure.
Conditions for Running the DTC
P0627 and P0629
| • | The ignition voltage is between 10-18.1 volts. |
| • | The ECM has commanded the fuel pump OFF. |
| • | The above conditions are met for greater than 1 second. |
| • | The DTCs run continuously once the above conditions are met. |
P0628
| • | The ignition voltage is between 10-18.1 volts. |
| • | The ECM has commanded the fuel pump 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 C DTCs.
Conditions for Clearing the DTC
DTCs P0627, P0628, and P0629 are Type C DTCs.
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
Note: Repair all U-codes before performing this diagnostic.
- Ignition OFF, disconnect the harness connector at the K27 FPCM.
- Install a test lamp between the fuel pump control circuit terminal 13 and ground. Verify the test lamp turns ON and OFF as the ignition is turned ON.
- Ignition ON, verify that a test lamp does not stay illuminated between the fuel pump control circuit terminal 13 and ground.
- If all circuits test normal, test or replace the K27 FPCM.
| ⇒ | If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 ECM. |
| ⇒ | If the test lamp stays illuminated, test the control circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for ECM or FPCM replacement, setup, and programming
