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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1599 (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 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. 1:  This step verifies that the retained accessory power (RAP) power mode function is malfunctioning by checking functions internally enabled by the BCM.
  2. 4:  The body control module (BCM) sends class 2 messages to other control modules via the serial data link, allowing them to operate in RAP power mode. 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.
  3. 5:  This step is checking for DTCs in the BCM.
  4. 6:  The presence of DTCs which begin with "U" indicate that other module is not communicating. The specified procedure will compile all the available information before tests are performed.
Diagnostic System Check - Retained Accessory Power

Step Action Yes No
Schematic Reference: Retained Accessory Power (RAP) Schematics 
Connector End View Reference: MASTER ELECTRICAL COMPONENT LIST in Wiring Systems
1 
  1. Turn key to the ON position.
  2. Close all vehicle doors.
  3. Turn key to the OFF position.
  4. Attempt to operate all of the following functions that are equipped on the vehicle:
    • Sunroof (Trailblazer, Envoy, Bravada)
    • Right and left rear power windows (Trailblazer, Envoy, Bravada)
    • Right and left rear quarter power vent windows (Bravada)
Does RAP function properly for one or more of the above accessories?		 Go to CONTROL MODULE REFERENCES in Body Control Systems for the applicable Diagnostic Systems Check for the system that does not operate Go to Step 2 
2 Install a scan tool.
Does the scan tool power up?		 Go to Step 3  Go to SCAN TOOL DOES NOT POWER UP 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 
  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to communicate the BCM.
Does the scan tool communicate with the BCM?		 Go to Step 5  Go to SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 Device (W/O Immobilizer) in Data Link Communications.
5  Select the body control module display DTCs function on the scan tool.
Does the scan tool display any DTCs?		 Go to Step 6  Go to Symptoms - Retained Accessory Power 
6  Does the scan tool display any DTCs which begin with a "U"? Go to DIAGNOSTIC TROUBLE CODE (DTC) LIST in Data Link Communications Go to Step 7 
7 Compare the DTCs listed below to the scan tool:
Are any of the DTCs shown on the scan tool?		  
Go to DIAGNOSTIC TROUBLE CODE (DTC) LIST		 Go to Step 8 
8 Does the scan tool display DTC B1445? Go to DTC B1445  Refer to CONTROL MODULE REFERENCES in Body Control Systems for the applicable sub-section/DTC procedure
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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.
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