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 920 (DATA LINK COMMUNICATIONS SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESSCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICETEST DESCRIPTION
2003 Chevrolet TrailBlazer 4.2 S, 4WD
Test Description
2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Test Description
WARNING: This page is about a different car, the 2003 GMC Sonoma, 2003 GMC Jimmy, 2003 Chevrolet S10 Pickup, and 2003 Chevrolet Blazer. 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.
- 2. A partial loss of communication in the class 2 serial data circuit uses a different procedure than a total loss of communication of the class 2 serial data circuit.
- 4. The following DTCs may be retrieved with a history status. These DTCs are not the cause of the present condition.
- U 1300
- U 1301
- U 1305
- 6. A State of Health DTC with a history status may be present along with a U1000 or U1255 with a current status. This indicates that the malfunction occurred when the ignition was on.
- 10. Normal class 2 serial data communication cannot take place until the body control module (BCM) sends the appropriate power mode message. If the BCM does not send a wake-up message, other modules on the class 2 serial data circuit may not communicate.
- 12. Normal class 2 serial data communication cannot take place until the body control module (BCM) sends the appropriate power mode message. If the BCM does not send a wake-up message, other modules on the class 2 serial data circuit may not communicate.
- 17. If there are no current DTCs that begin with the letter "U", the communication concern has been repaired.
- 18. The communication concern may have prevented diagnosis of the customer complaint.
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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.