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 P1A93: 14 Volt Power Module Stuck OffDTC 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 wakeup signal.
Diagnostic Aids
P1A93
| • | Electrical failure in SGCM, open circuit or open fuse |
| • | FET breakdown |
P1A94
FET breakdown
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Starter/Generator Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
Caution: To help avoid personal injury, be careful when working in the vicinity of the generator battery disconnect control module. Internal components will still be live, 36V potential, even when the cover has been opened or removed.
- Gain access to the 12 volt 175 amp SGCM maxi fuse. Refer to Generator Control Module Cover Replacement
- Test for B+ at 175 amp maxi fuse.
- With a scan tool, clear the DTC.
- Ignition OFF, wait 30 seconds.
- Ignition ON, operate the vehicle within the Conditions for Running the DTC.
| ⇒ | If less than specified value, test the supply voltage circuit for a short to ground or an open/high resistance. |
| ⇒ | If the DTC resets, replace the SGCM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for SGCM replacement, setup, and programming
