| Table 1: | SGCM to MGU Terminal Reference Table |
| Table 2: | MGU to SGCM Specification Table |
| Table 3: | SGCM to MGU Specification Table |
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 Descriptor
DTC P0A4B: Starter/Generator Position Sensor CircuitCircuit/System Description
The motor generator unit (MGU) position sensor is used for determining motor control of the MGU. The motor control consists of the angular position and speed of the MGU. The rotor is bolted on the MGU shaft, the stator is bolted on the MGU bracket and the sensor circuit is soldered on the motor control board in the starter/generator control module (SGCM). The SGCM monitors the position sensor circuit to detect a converter error (loss of speed signal or tracking).
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
R/D converter error (loss of signal or tracking) for 100 ms
Action Taken When the DTC Sets
Stop PWM (MGU shutdown)
Conditions for Clearing the DTC
Clears 30 seconds after cycle wake up signal.
Diagnostic Aids
| • | Possible internal sensor short to ground, short to voltage or open/high resistance. |
| • | Possible MGU or SGCM fault |
| • | Possible wiring harness short to ground, short to voltage or open/high resistance. |
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
- Disconnect the MGU X2 and the SGCM X2 connectors. Refer to Generator with Starter Replacement and Generator Control Module Replacement.
- Test the circuits in the SGCM to MGU Terminal Reference Table as indicated below. Also test these circuits for short to ground.
- Reconnect SGCM connector X2.
- Test the circuits in the MGU to SGCM Specification Table to ground as indicated below.
- Reconnect the MGU X2 connector and disconnect the SGCM X2 connector. Refer to Generator with Starter Replacement and Generator Control Module Replacement.
- Test the circuits in the SGCM to MGU Specification Table as indicated below.
| ⇒ | If any of the circuits are not within specification, check for an open/high resistance or short to ground. |
| ⇒ | If any of the circuits are not within the specified range, replace the SGCM. |
| ⇒ | If all circuits test normal, replace the MGU. |
MGU Connector/Terminal | SCGM Connector/Terminal | Minimum Resistance | Maximum Resistance |
|---|---|---|---|
Harness Continuity Test | |||
B | X2/7 | -- | less than 1 ohm |
C | X2/6 | -- | less than 1 ohm |
D | X2/4 | -- | less than 1 ohm |
E | X2/17 | -- | less than 1 ohm |
F | X2/20 | -- | less than 1 ohm |
G | X2/19 | -- | less than 1 ohm |
H | X2/5 | -- | less than 1 ohm |
MGU Connector/Terminal | Signal Name | Minimum Resistance | Maximum Resistance |
|---|---|---|---|
Measurements made to ground. SGCM connected and MGU disconnected. | |||
D | REZ- | 1.6k ohms | 2k ohms |
H | REZ+ | 1.6k ohms | 2k ohms |
C | REZ3 | Over 1 M ohm | -- |
B | REZ4 | Over 1 M ohm | -- |
E | REZGS (GND) | -- | less than 5 ohm |
G | REZ1 | Over 1 M ohm | -- |
F | X2/5 | Over 1 M ohm | -- |
SGCM Connector/Terminal | SGCM Connector/Terminal | Minimum Resistance | Maximum Resistance |
|---|---|---|---|
MGU connected and SGCM disconnected. | |||
X2/4 | X2/5 | 20.1 ohms | 26.7 ohms |
X2/6 | X2/19 | 32.4 ohms | 43.0 ohms |
X2/7 | X2/20 | 32.9 ohms | 43.5 ohms |
X2/4 | X2/6 | Over 1 meg ohm | -- |
X2/4 | X2/7 | Over 1 meg ohm | -- |
X2/6 | X2/7 | Over 1 meg ohm | -- |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Generator with Starter Replacement for MGU replacement |
| • | Control Module References for SGCM replacement, setup, and programming |
