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 MANUALSCHEVROLET2009TAHOE BASE, 4.8 CREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT VARIANT/TRIMSECTION 21 (HYBRID COOLING SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESDTC P0A81CIRCUIT/SYSTEM TESTING
2009 Chevrolet Tahoe Base, 4.8 C
Circuit/System Testing
2009 Chevrolet Tahoe Base, 4.8 CSECTION Circuit/System Testing
WARNING: This page is about a different variant/trim than selected.
- Identify how to disable high voltage.
- Identify how to test for the presence of high voltage.
- Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed.
- Ignition OFF, disable the high voltage at the drive motor generator battery. Refer to High Voltage Disabling .
- Remove the drive motor generator battery case upper cover, front cover, and right side cover.
- Disconnect the harness connector at the battery vent fan motor.
- Connect a test lamp between the ignition circuit terminal 2 and ground.
- Ignition OFF, connect the 12 V battery.
- Ignition ON, command the battery pack vent fan speed to 60 percent. The test lamp should illuminate after a 5-7 second delay.
- If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
- Verify a test lamp illuminates between B+ and the ground circuit terminal 3.
- If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
- Ignition OFF, connect the harness connector at the battery vent fan motor.
- Disconnect X2 harness connector at the GBCM.
- Verify a test lamp illuminates between the vent fan relay control circuit terminal 7 and ground.
- If the test lamp does not illuminate, test the control circuit for an open/high resistance. If the circuit tests normal, replace the generator battery vent fan relay.
- Connect a 3 A fused jumper wire between the vent fan motor relay control circuit terminal 7 and ground.
- Ignition ON, test for 4.8-5.2 V between the signal circuit terminal 2 and ground.
- If the voltage is not within the specified range, test the signal circuit for a short to voltage, short to ground, or an open/high resistance. If the circuit tests normal, replace the generator battery vent fan.
- If all circuits test normal, replace the drive motor generator battery control module.
WARNING:
Always perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed.
The High Voltage Disabling procedure will perform the following tasks:
Failure to follow the procedures exactly as written may result in serious injury or death.
The High Voltage Disabling procedure will perform the following tasks:
Failure to follow the procedures exactly as written may result in serious injury or death.
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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.