Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET2008CHEVY EXPRESS G2500, VAN CARGO, 6.6 6REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 845 (HYBRID CONTROL SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESDTC P0A4BCIRCUIT/SYSTEM TESTING
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6
Circuit/System Testing
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6SECTION Circuit/System Testing
WARNING: This page is about a different car, the 2007 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
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 starter/generator control module (SGCM) connector C2. Refer to Generator Control Module Replacement .
- Test the circuits in the SGCM to MGU Specification Table from the C2 connector to ground.
- If all of the circuits are within the minimum or maximum values specified, replace the SGCM.
- Disconnect the MGU 10-pin connector. Refer to Generator with Starter Replacement .
- Test the circuits in the SGCM to MGU Terminal Reference Table for an open, short to ground or high resistance.
- If all circuits test normal, replace the MGU.
SGCM to MGU Specifications
| SGCM Connector/Terminal | Signal Name | Minimum Resistance | Maximum Resistance |
|---|---|---|---|
| C2/4 | REZ- | 1.6 K ohm | 2 k ohm |
| C2/5 | REZ+ | 1.6 K ohm | 2 k ohm |
| C2/6 | REZ3 | Over 1 meg ohm | - |
| C2/7 | REZ4 | Over 1 meg ohm | - |
| C2/17 | REZGS (GND) | - | less than 5 ohm |
| C2/18 | REZGS (GND) | - | less than 5 ohm |
| C2/19 | REZ1 | Over 1 meg ohm | - |
| C2/20 | REZ2 | Over 1 meg ohm | - |
SGCM to MGU Terminal Reference
| MGU 10 Pin Connector/Terminal | SCGM Connector/Terminal | Minimum Resistance | Maximum Resistance |
|---|---|---|---|
| B | C2/7 | - | less than 1 ohm |
| C | C2/6 | - | less than 1 ohm |
| D | C2/4 | - | less than 1 ohm |
| E | C2/17 and 18 | - | 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 |
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.