P1A93

DTC P1A93 or P1A94

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 P1A93
- 14 Volt Power Module Stuck Off

DTC P1A94
- 14 Volt Power Module Stuck On

Circuit/System Description

The starter/generator control module (SGCM) monitors auxiliary power module (APM) On/Off, DC - DC direction is commanded On but converter is Off to check the status of the 14 volt power module. The SGCM also monitors to detect if the APM On when it is not commanded On causing a large current output. If a fault is detected, the appropriate DTC will set.

Conditions for Running the DTC

P1A93, P1A94

The engine is running.

Conditions for Setting the DTC

P1A93

In normal charge mode, 12-volt output voltage - 12-volt command voltage is greater than 0.2 volt for 1 second.

P1A94

DC-DC direction is Off, but converter remains On and APM current is greater than +/-20 amps for 1 second.

Action Taken When the DTC Sets

P1A93, P1A94
* Stop PWM (MGU shutdown)
* APM PWM off
* Battery disconnection (disconnect SW on/off)

Conditions for Clearing the DTC

P1A93, P1A94

Clears 30 seconds after cycle wake-up signal.

Diagnostic Aids

P1A93
* Electrical failure in SGCM, open circuit or open fuse
* FET breakdown

P1A94

FET breakdown

Reference Information
Schematic Reference

Hybrid Controls Schematics (Hybrid Controls Schematics)
Connector End View Reference

Component Connector End Views (Connector End Views By Name)
Description and Operation

Starter/Generator Description and Operation (Description and Operation)
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)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Testing

Warning

To help avoid personal injury, be careful when working in the vicinity of the battery energy control module. Internal components will still be live, 36V potential, even when the cover has been opened or removed.

Note: If DTC is history, refer to Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)

1. Gain access to the UBEC B+ terminal.
2. Verify the difference between the scan tool Desired APM Voltage value and the actual voltage on the UBEC B+ terminal is greater than 0.2V.

• If less than specified value, test the B+ circuit for a short to ground or an open/high resistance. If the circuit test normal, replace the SGCM.

3. Gain access to the 12 volt 175 amp SGCM maxi fuse.
4. Test for B+ at 175 amp maxi fuse.

• If less than specified value, test the supply voltage circuit for a short to ground or an open/high resistance.

5. Check the B+ connections at the UBEC and underhood auxiliary BEC B+ terminals.
6. With a scan tool, clear the DTC.
7. Ignition OFF, wait 30 seconds.
8. Ignition ON, operate the vehicle within the Conditions for Running the DTC.

• If the DTC resets and all circuits test normal, replace the SGCM.

Repair Instructions

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

Control Module References (Programming and Relearning) for SGCM replacement, setup, and programming