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 P12A4: Fuel Pump Enable Circuit Low VoltageDTC P12A5: Fuel Pump Enable Circuit High Voltage
DTC P12A6: Fuel Pump Enable Circuit Performance
Diagnostic Fault Information
Circuit | Short to Ground | Open or High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Fuel Pump PWM Control | P12A0 | P12A0 | P12A1 | P12A2 |
Fuel Pump Enable Control | P12A4 | P12A4 | P12A5 | P12A6 |
Circuit/System Description
The engine control module (ECM) supplies voltage to the fuel pump 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 provides a control enable input circuit to the FPCM relay to turn the 3-phase fuel pump ON and OFF. The control enable input circuit is switched to ground to turn ON the pump. The FPCM also sends a 400 HZ PWM on a signal circuit to the FPCM relay to control the fuel pump speed by varying the duty cycle of this signal.
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
DTC P12A4
| • | The DTC sets when the FPCM relay enable circuit low diagnostic is to determine if the state of the FPCM relay enable circuit is low (active) when it should be high (inactive). To make such a determination, the voltage level of the FPCM relay enable circuit as sensed by the FPCM output circuit is evaluated. |
| • | The above condition is present for greater than 12.5 milliseconds. |
DTC P12A5
| • | The DTC sets when the FPCM relay enable circuit high diagnostic is to determine if the state of the FPCM relay Enable circuit is high (inactive) when it should be low (active). To make such a determination, the voltage level of the FPCM relay enable circuit as sensed by the FPCM output circuit is evaluated. |
| • | The above condition is present for greater than 12.5 milliseconds. |
DTC P12A6
| • | The DTC sets when the FPCM relay enable circuit rationality diagnostic is to detect inconsistencies between the FPCM relay sensed state of the FPCM relay enable circuit and the FPCM commanded state of the FPCM relay enable circuit. |
| • | The above condition is present for greater than 12.5 milliseconds. |
Actions Taken When the DTC Sets
DTCs P12A4 -- P12A6 and are Type A DTCs.
Conditions for Clearing the DTC
| • | The condition responsible for setting the DTC no longer exists. |
| • | A history DTC will clear after 100 malfunction-free ignition cycles have occurred. |
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
Connector End View Reference
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Fuel Pump Flow Control Module Scan Tool Information for scan tool information
Circuit/System Verification
Ignition ON, command the fuel pump ON and OFF using the scan tool ECM output control. The fuel pump should turn ON and OFF.
Circuit/System Testing
- Ignition OFF, disconnect the X2 harness connector at the FPCM relay.
- Connect a test lamp between the enable circuit terminal 2 and B+.
- Ignition ON, the test lamp should turn ON.
- If all circuits test normal, replace the FPCM relay.
| ⇒ | If the test lamp is OFF, test the enable circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the FPCM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for FPCM replacement, setup, and programming |
