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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1545 (CELLULAR COMMUNICATION SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESDIAGNOSTIC SYSTEM CHECK - CELLULAR COMMUNICATIONTEST 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 2002 Oldsmobile Bravada, 2002 GMC Envoy XL, 2002 GMC Envoy, and 2002 Chevrolet TrailBlazer. 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. 2:  Lack of communication may be due to a partial malfunction or a total malfunction of the class 2 serial data circuit. The specified procedure will determine the condition.
  2. 5:  The presence of DTCs which begin with "U" indicate some other system control module is not communicating.
Diagnostic System Check - Cellular Communication

Step Action Yes No
1 Install a scan tool.
Does the scan tool power up?		 Go to Step 2  Go to SCAN TOOL DOES NOT POWER UP in Data Link Communications
2 
  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to establish communication with the Vehicle Communication Interface Module (VCIM).
Does the scan tool communicate with the VCIM?		 Go to Step 3  Go to SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 Device (W/O Immobilizer) in Data Link Communications
3
IMPORTANT: The engine may start during the following step. Turn OFF the engine as soon as you have observed the Crank power mode.
  1. Access the Class 2 Power Mode in the Diagnostic Circuit Check on the scan tool.
  2. Rotate the ignition switch through all positions while observing the ignition switch power mode parameter.
Does the ignition switch parameter reading match the ignition switch position for all switch positions?		 Go to Step 4  Go to POWER MODE MISMATCH in Body Control System
4 Select the display DTCs function on the scan tool.
Does the scan tool display any DTCs?		 Go to Step 5  Go to OnStar Symptom Diagnosis 
5  Does the scan tool display any DTCs which begin with a "U"? Go to Step 6  Go to Step 7 
6 Does the scan tool display DTC U1500? Go to Diagnostic Trouble Code (DTC) List  Go to DIAGNOSTIC TROUBLE CODE (DTC) LIST in Data Link Communications
7 Does the scan tool display DTC B1000, B1004, B1007, or B1009? Go to DIAGNOSTIC TROUBLE CODE (DTC) LIST in Body Control System Go to Step 8 
8 Does the scan tool display DTC B1327 or B1328? Go to DIAGNOSTIC TROUBLE CODE (DTC) LIST in Engine Electrical Go to Diagnostic Trouble Code (DTC) List 
RENDER: 1.0x

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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.