P12A7
DTC P12A7
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 Descriptor
DTC P12A7
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Fuel Pump Phase U-V-W Circuit
Diagnostic Fault Information
Circuit/System Description
The FPCM Relay communicates with the FPCM via serial data. The FPCM Relay diagnostics are reported out via the FPCM. The FPCM Relay controls the brush-less, 3-phase fuel pump by providing variable, continuous PWM speed control. The nominal current supplied to the fuel pump is 15 amps, with a maximum limit of 25 Amps.
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
* The DTC sets when performing a diagnostic that monitors the state of health of the FPCM relay output circuits. The fuel pump control module categorizes fuel pump operation into one of three states: Indeterminate, Running or Faulted and then communicates the result to the FPCM over the serial data communication (CAN) circuits.
* The above condition is present for greater than 12.5 milliseconds.
Action Taken When the DTC Sets
DTCs P12A7 are Type B DTCs.
Conditions for Clearing the DTC
DTCs P12A7 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 DiagramsEngine Controls Schematics (LS7) [1][2]Electrical DiagramsEngine Controls Schematics (LS9) [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views 5 Bow Lowered Switch (CM7)
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 Control Module References for scan tool information
Circuit/System Verification
Ignition ON, command the fuel pump ON and OFF using the scan tool FPCM output control. The fuel pump should turn ON and OFF.
Circuit/System Testing
1. Ignition OFF, disconnect the X469 harness connector at the LH fuel tank jumper.
2. Ignition OFF, test for less than 1 ohms between the ground circuit terminal G and ground.
• If greater than the specified value, test the low reference circuit for an open/high resistance.
3. Ignition OFF, connect a test lamp between control circuit terminal A and ground. Ignition ON, command the fuel pump ON and OFF using the FPCM scan tool. The test lamp should turn ON and OFF, as commanded.
• If the test lamp is always ON, test circuit for a short to voltage. If the circuit tests normal, replace the FPCM relay.
• If the test lamp is always OFF, test circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the FPCM relay.
4. Ignition OFF, connect a test lamp between control circuit terminal B and ground. Ignition ON, command the fuel pump ON and OFF using the FPCM scan tool. The test lamp should turn ON and OFF, as commanded.
• If the test lamp is always ON, test circuit for a short to voltage. If the circuit tests normal, replace the FPCM relay.
• If the test lamp is always OFF, test circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the FPCM relay.
5. Ignition OFF, connect a test lamp between control circuit terminal C and ground. Ignition ON, command the fuel pump ON and OFF using the FPCM scan tool. The test lamp should turn ON and OFF, as commanded.
• If the test lamp is always ON, test circuit for a short to voltage. If the circuit tests normal, replace the FPCM relay.
• If the test lamp is always OFF, test circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the FPCM relay.
6. Disconnect the harness connector at the fuel pump.
7. Ignition OFF, test for less than 1 ohms between the ground circuit terminal 3 and ground.
• If greater than the specified value, test the ground circuit for an open/high resistance.
8. If all circuits test normal, perform the Fuel System Diagnosis. Refer to Fuel System Diagnosis (LS9) Fuel System DiagnosisFuel System Diagnosis (LS3 or LS7) Fuel System Diagnosis
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Fuel Pump Flow Control Module Replacement Fuel Pump Flow Control Module Replacement
* Fuel Pump Flow Control Module Relay Replacement Fuel Pump Flow Control Module Relay Replacement
* Control Module References Control Module References for FPCM replacement, setup, and programming