Buick Regal: DTC P157A

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 P157A

Sensor Supply Voltage Relay Feedback Circuit High Voltage

Circuit/System Description

There is 1 Sensor Supply Voltage Relay Feedback circuit supplied to the K111 Fuel Pump Driver Control Module from the K20 Engine Control Module.

Conditions for Running the DTC

P157A

The DTC runs continuously when Ignition OFF.

Conditions for Setting the DTC

P157A

The ECM detects that the voltage level difference is greater than 11 V between the Wake Up/Enable Voltage and battery supply voltage circuits for greater than 1 s.

Action Taken When the DTC Sets

DTC P157A is a Type B DTC.

Conditions for Clearing the DTC

DTC P157A is a Type B DTC.

Diagnostic Aids

The sensor bus relay may also be labeled the sensor supply voltage relay, sensor bus relay control circuit, or sensor supply voltage feedback circuit.

Reference Information

Schematic Reference

• Engine Controls Wiring Schematics (LGX)
• Power Distribution Wiring Schematics

Connector End View Reference

Component Connector End View Index

Component View Reference

Powertrain Component Views

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Electrical Center Identification Views
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

NOTE: An open on this circuit may cause DTC U18A2 to set. If any other DTC is set, diagnose that DTC first.

1. Ignition ON, observe the scan tool DTC information. Verify DTC P157A is not set.

• If DTC P157A is set

Refer to Circuit/System Testing.

• Go to next step: If DTC P157A is set

2. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

• If the DTC sets

Refer to Circuit/System Testing.

• Go to next step: If the DTC does not set

3. All OK.

Circuit/System Testing

1. Ignition Off, disconnect the harness connector at the K111 Fuel Pump Driver Control Module.

2. Ignition On.

3. Test for greater than 11 V between control circuit terminal 2 at the K111 Fuel Pump Driver Control Module harness connector and ground.

• If 11 V or greater

Replace the K111 Fuel Pump Driver Control Module

• Go to next step: If less than 11 V

4. Ignition Off, disconnect the harness connector: X3 at the K20 Engine Control Module.

5. Test for less than 1 V between control circuit terminal 2 at the K111 Fuel Pump Driver Control Module harness connector and ground.

• If 1 V or greater, repair the short to voltage on the circuit
• Go to next step: If less than 1 V

6. Test for infinite resistance between control circuit terminal 2 at the K111 Fuel Pump Driver Control Module harness connector and ground.

• If less than infinite resistance, repair the short to ground on the circuit
• Go to next step: If infinite resistance

7. Test for less than 2 Ω between test points: terminal X3-3 at the Engine Control Module harness and terminal 2 at the K111 Fuel Pump Driver Control Module harness.

• If 2 Ω or greater, repair the open/high resistance in the circuit
• Go to next step: If less than 2 Ω

Go to next step: Replace the K20 Engine Control Module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Engine Wiring Harness Junction Block Replacement (LTG) or Engine Wiring Harness Junction Block Replacement (LGX).
• Relay Replacement (Attached to Wire Harness) or Relay Replacement (Within an Electrical Center)
• Control Module References for engine control module replacement, programming, and setup.

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