P12A6

DTC P12A4-P12A6

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.

DTC Descriptors
DTC P12A4
- Fuel Pump Enable Circuit Low Voltage

DTC P12A5
- Fuel Pump Enable Circuit High Voltage

DTC P12A6
- Fuel Pump Enable Circuit Performance

Diagnostic Fault Information





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

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.

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.

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 B DTCs.

Conditions for Clearing the DTC

DTCs P12A4-P12A6 and 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 (LS3) ([1][2]Electrical Diagrams) Engine Controls Schematics (LS7) ([1][2]Electrical Diagrams) Engine Controls Schematics (LS9) ([1][2]Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing For Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference

Control Module References (Programming and Relearning) 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

1. Ignition OFF, disconnect the X2 harness connector at the FPCM relay.
2. Connect a test lamp between the enable circuit terminal 2 and B+.
3. Ignition ON, the test lamp should turn ON.

• 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.

4. If all circuits test normal, replace the FPCM relay.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Fuel Pump Flow Control Module Replacement (Service and Repair)
* Fuel Pump Flow Control Module Relay Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for FPCM replacement, setup, and programming