• | 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. |
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 | -- | -- |
|
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.
• | 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 when the conditions above are met. |
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 of 30 seconds.
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 of 30 seconds.
The ECM detects the fuel pump relay control circuit voltage is greater than 2.74 volts when the control circuit is commanded OFF. The condition exists for greater than 4 seconds, or a cumulative of 30 seconds.
• | DTCs P0627 and P0628 are Type C DTCs. |
• | DTC P0629 is a Type B DTC. |
• | DTCs P0627 and P0628 are Type C DTCs. |
• | DTC P0629 is a Type B DTC. |
• | When disconnecting electrical connectors or removing fuses and relays from a fuse block, always inspect the component electrical terminals for corrosion and the correct orientation in the fuse block. Test the mating electrical terminals for tightness. |
• | If the condition is intermittent, move the related harnesses and connectors, with the engine operating, while monitoring the scan tool circuit test status parameters for the component. The circuit test status parameter changes from OK or Not Run to Fault if there is a condition with the circuit or a connection. |
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Control Module References for scan tool information
⇒ | 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. |
⇒ | If the test lamp does not turn ON when commanded, repair the open/high resistance in ground circuit of the fuel pump relay. |
⇒ | If not within the specified range, replace the ECM. |
⇒ | If not within the specified range, replace the fuel pump relay. |
• | 30 and 86 |
• | 30 and 87 |
• | 30 and 85 |
• | 85 and 87 |
⇒ | If less than the specified value, replace the fuel pump relay. |
⇒ | If greater than the specified range, replace the fuel pump relay. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Control Module References for engine control module replacement, setup, and programming |