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 MANUALSCHEVROLET2006CHEVY EXPRESS G2500, VAN CARGO, 6.6 2REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1534 (DATA COMMUNICATION SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESDTC U1821CIRCUIT/SYSTEM TESTING
2006 Chevrolet Chevy Express G2500, Van Cargo, 6.6 2
Circuit/System Testing
2006 Chevrolet Chevy Express G2500, Van Cargo, 6.6 2SECTION Circuit/System Testing
WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
- 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 .
- Ignition OFF, disconnect harness connector X4 of the accessory DC power control module.
- Test for less than 1.0 ohm between the accessory DC power control module connector terminal and ground.
- If greater than the specified value, test the ground circuit for an open/high resistance.
- Ignition ON, disconnect harness connector X3 of the accessory DC power control module.
- Verify that a test lamp illuminates between the accessory DC power control module connector terminal A and ground.
- If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
- Ignition OFF, disconnect harness connector X1 of the accessory DC power control module and the drive motor generator power inverter module.
- Test for less than 1.0 ohm at the accessory DC power control module connector and drive motor generator power inverter module connector between the following connector serial data terminals.
- Accessory DC power control module terminal 1 and drive motor generator power inverter module terminal 24
- Accessory DC power control module terminal 2 and drive motor generator power inverter module terminal 25
- If greater than the specified value, test the serial data circuits for an open/high resistance.
- Test for infinte resistance between the accessory DC power control module terminal 2 and accessory DC power control module terminal 1.
- If less than the specified value, test the serial data circuits for a short between the circuits.
- If all circuits test normal, replace the accessory DC power 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.