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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1638 (RETAINED ACCESSORY POWER SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESDIAGNOSTIC SYSTEM CHECK - RETAINED ACCESSORY POWERTEST 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 7 other vehicles, including the 2002 GMC Yukon XL, 2002 GMC Yukon, 2002 Chevrolet Tahoe, 2002 Chevrolet Suburban, and 2002 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. 2:  Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.
  2. 4:  This step is checking for DTCs in the BCM.
  3. 5:  This step is checking for RAP specific DTCs.
Diagnostic System Check - Retained Accessory Power

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
2 
  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to establish communication with the body control module.
Does the scan tool communicate with the BCM?		 Go to Step 3  Go to SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE
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 Class 2 Power Mode on the Scan Tool. Refer to the Serial Data Power Mode table within the BODY CONTROL SYSTEM DESCRIPTION AND OPERATION , for a list of the power mode states that correspond to each ignition switch position.
Does the Class 2 Power Mode parameter reading match the ignition switch position for all the selected positions?		 Go to Step 4  Go to POWER MODE MISMATCH
4  Select the BCM display DTCs function on the scan tool.
Does the scan tool display any DTCs?		 Go to Step 5  Go to the Symptoms list in the appropriate service category
5  Does the scan tool display B1477 or B1478? Go to Diagnostic Trouble Code (DTC) List  Go to Symptoms - Retained Accessory Power 
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.