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 MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 807 (DATA LINK COMMUNICATIONS SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESDTC U1000 AND U1255: NODE ALIVE MESSAGE HAS NOT BEEN RECEIVED FROM AN UNIDENTIFIED MODULETEST DESCRIPTION
2003 Chevrolet TrailBlazer 4.2 S, 4WD
Test Description
2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Test Description
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2003 GMC Yukon XL, 2003 GMC Yukon, 2003 Chevrolet Tahoe, 2003 Chevrolet Suburban, and 2003 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
The numbers below refer to the step numbers on the diagnostic table.
- 1. DTC U1001 - U1254 Lost Communications with XXX with a history status may indicate the cause of U1000 or U1255.
- 2. The modules not communicating are the likely cause of U1000 or U1255. The modules that are available on the class 2 serial data circuit are listed in the Circuit Description.
- 6. The modules which was not communicating due to a poor connection to the class 2 serial data circuit may have set DTC U1001 - U1254 Lost Communications with XXX for those modules that it was monitoring.
- 9. The modules which can communicate indicate the module which cannot communicate. You must clear the serial data communication DTCs from these modules to avoid future misdiagnosis.
- 12. If all modules are communicating, the module which set U1000 or U1255 may have done so due to some other condition.
- 14. The module which set U1000 or U1255 is the likely cause of the malfunction.
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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.