• Perform the Diagnostic System Check prior to using this diagnostic procedure:Diagnostic System Check - Vehicle
• Review the description of Strategy Based Diagnosis:Strategy Based Diagnosis
• An overview of each diagnostic category can be found here:Diagnostic Procedure Instructions

Symptom Byte Information:Symptom Byte List

The device serves as a voltage stabilizer for several vehicle systems by compensating the voltage drop that the starter motor causes while starting the engine.

For an overview of the component/system, refer to:Stop/Start System Description and Operation

• Ignition » On / Vehicle » In Service Mode
• Ignition Voltage=Greater than 11 V

Message Counter Incorrect=If 10 counts—For greater than 3 s

• DTC P156D=Type B DTC

• DTC P156D=Type B DTC

Starting and Charging Schematics

Master Electrical Component List

Stop/Start System Description and Operation

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Control Module References

1. Ignition » On / Vehicle » In Service Mode
2. Verify there are no other DTCs set, except for DTC P156D.
• If any other DTCs are set

  Refer to:Diagnostic Trouble Code (DTC) List - Vehicle

• If only DTC P156D is set
3. Replace the component:T19 Power Supply Transformer
4. Verify the DTC does not set.
• If the DTC sets » Replace the component:K20 Engine Control Module
• If the DTC does not set
5. All OK.

• Perform the Diagnostic Repair Verification after completing the repair:Diagnostic Repair Verification
• For control module replacement, programming, and setup refer to:Control Module References