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Home >> Cadillac >> 2007 >> Escalade EXT >> Repair and Diagnosis >> External Pages >> Different car >> Section 405 (Retained Accessory Power System) >> Diagnostic Information and Procedures >> Diagnostic System Check - Retained Accessory Power >> Test Description
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Test Description

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. 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. 3:  This step tests for valid system power moding in all ignition switch positions.
  3. 5:  The presence of DTCs which begin with "U" indicate some 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: Data Link Connector (DLC) Schematics in Data Link Communications
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 body control module.
Does the scan tool communicate with the body control module?		 Go to Step 3  Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications
3 
IMPORTANT: Open the driver door and leave it open during this test. This will disable the RAP power mode and eliminate this power mode from the power mode parameter list.
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 parameter in the diagnostic circuit check menu on the scan tool.
  2. Rotate the ignition switch through all positions while observing the class 2 power mode parameter.
Does the class 2 power mode 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 body control module display DTCs function on the scan tool.
Does the scan tool display any DTCs?		 Go to Step 5  Go to Step 7 
5  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 6 
6 Does the scan tool display DTC B1000 or B1440? Go to Diagnostic Trouble Code (DTC) List in Body Control System Go to Step 7 
7 Test the Courtesy Lamps for proper operation after closing and opening each door. Refer to Interior Lighting Systems Description and Operation in Lighting Systems.
Do the Courtesy Lamps operate properly?		 Go to Symptoms - Retained Accessory Power  Go to Symptoms - Lighting Systems in Lighting Systems
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