| Table 1: | SGCM to MGU Terminal Reference |
| Table 2: | MGU to SGCM Specification |
| Table 3: | SGCM to MGU Specification |
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 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 sensor cable short to ground, short to voltage or open. |
| • | Possible MGU or SGCM fault. |
| • | Possible wiring harness fault. |
Reference Information
Schematic Reference
Connector End View Reference
Hybrid Controls Connector End Views
Electrical Information Reference
Scan Tool Reference
Circuit/System Testing
Caution: To help avoid personal injury, additional precautions must be taken prior to working on the generator control module or the generator starter. After removing the 36V battery cables from the generator battery, remove both engine wiring harness connectors from the generator control module. Wait at least 5 minutes and then remove the generator control module cover. Verify voltage levels at all 36V, 12V, and 3-phase connections, are less than 3 volts using a DMM before proceeding.
- Disconnect the MGU C2 and the SGCM C2 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 check these circuits for short to ground.
- Reconnect SGCM connector C2.
- Test the circuits in the MGU to SGCM Specification Table to ground as indicated below.
- Reconnect the MGU C2 connector and disconnect the SGCM C2 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, repair the 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 | C2/7 | -- | less than 1 ohm |
C | C2/6 | -- | less than 1 ohm |
D | C2/4 | -- | less than 1 ohm |
E | C2/17 | -- | less than 1 ohm |
F | C2/20 | -- | less than 1 ohm |
G | C2/19 | -- | less than 1 ohm |
H | C2/5 | -- | less than 1 ohm |
MGU Connector/Terminal | Signal Name | Minimum Resistance | Maximum Resistance |
|---|---|---|---|
Measurements made to ground. SGCM connected and MGU disconnected. | |||
D | REZ- | 1.6 K ohms | 2 K ohms |
H | REZ+ | 1.6 K ohms | 2 K ohms |
C | REZ3 | Over 1 M ohm | - |
B | REZ4 | Over 1 M ohm | -- |
E | REZGS (GND) | -- | less than 5 ohms |
G | REZ1 | Over 1 M ohm | -- |
F | C2/5 | Over 1 M ohm | -- |
SGCM Connector/Terminal | SGCM Connector/Terminal | Minimum Resistance | Maximum Resistance |
|---|---|---|---|
MGU connected and SGCM disconnected. | |||
C2/4 | C2/5 | 20.1 ohms | 26.7 ohms |
C2/6 | C2/19 | 32.4 ohms | 43.0 ohms |
C2/7 | C2/20 | 32.9 ohms | 43.5 ohms |
C2/4 | C2/6 | Over 1 M ohm | -- |
C2/4 | C2/7 | Over 1 M ohm | -- |
C2/6 | C2/7 | Over 1 M 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 |
