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Vehicle On-Board Diagnostic System Check

NOTE: Use this check as the starting point for any Body Control Module (BCM) complaint. BCM is a very reliable component, and is not likely the cause of malfunction. Most malfunctions are caused by faulty wiring, connectors or components. If DTC P1300 or P1301 is set in any control module, diagnosis these codes first before performing any other testing procedure.
  1. Connect scan tool to Data Link Connector (DLC). Turn ignition on. If scan tool powers up, go to next step. If scan tool does not power up, go to TEST A: SCAN TOOL DOES NOT POWER UP under SYSTEM TESTS in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
  2. Attempt to establish communication with Body Control Module (BCM), Sensing and Diagnostic Module (SDM), Powertrain Control Module (PCM) and Electronic Brake/Traction Control Module (EBTCM). Read and record any Diagnostic Trouble Codes (DTCs) that may be set in any of the modules. If scan tool communicates with BCM, go to step  4 . If scan tool does not communicate with BCM, go to next step.
  3. If scan tool communicates with SDM, go to DTC U1064: LOST COMMUNICATIONS WITH BODY CONTROL MODULE under DIAGNOSTIC TESTS in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. If scan tool does not communicate with SDM, go to TEST B: NO COMMUNICATION ON CLASS 2 DATA LINK under SYSTEM TESTS in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
  4. If any BCM DTCs exist, perform appropriate test. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. If no BCM DTCs exist, go to next step.
  5. If any PCM DTCs exist that begin with a "U", diagnosis these DTCs first. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. If any other PCM DTCs exist, perform appropriate test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS  table. If no PCM DTCs exist, go to next step.
  6. If vehicle is equipped with an anti-lock brake system, go to next step. If vehicle is not equipped with an anti-lock brake system, go to step  8 .
  7. If any EBTCM DTCs exist, repair anti-lock brake system. See appropriate ANTI-LOCK article in BRAKES. If no EBTCM DTCs exist, go to next step.
  8. If vehicle starts and runs, test is complete. Repair charging system by symptom. See CHARGING SYSTEM TEST  under ON-VEHICLE TESTING. If vehicle does not start and run, repair by symptom. See appropriate TROUBLE SHOOTING - NO CODES article in ENGINE PERFORMANCE.
DIAGNOSTIC TROUBLE CODE DEFINITIONS

DTC Description
P0562  System Voltage Out Of Range-Low
P0563  System Voltage Out Of Range-High
P0621  Generator "L" Terminal Circuit Low Voltage
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