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Diagnostic Procedures

DO NOT perform this test if no driveability condition exists. Search for applicable Technical Service Bulletins (TSB) before proceeding with the diagnosis. DO NOT turn OFF ignition when performing this diagnostic test procedure. DO NOT clear the DTCs unless the diagnostic instructs you to do so. If there is a condition with the starter system, diagnose starter system. See appropriate STARTERS article in ELECTRICAL. Ensure the battery has a full charge. Ensure the battery cables are clean and tight. Ensure the ECM grounds are clean, tight, and in the correct location. Ensure the resistance between the ECM housing and the battery negative cable is less than 2 ohms.

  1. Install scan tool. Does scan tool turn ON? If yes, go to next step. If no, perform SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
  2. Turn ignition on, with engine off. Using scan tool, attempt to establish communication with the Engine Control Module (ECM) and Transmission Control Module (TCM). Does scan tool communicate with all the control modules? If yes, go to next step. If no, perform SCAN TOOL DOES NOT COMMUNICATE WITH KEYWORD DATA LINE in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
  3. Attempt to start engine. Does engine start and idle? If yes, go to next step. If no, go to NO-START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES - 3.2L CTS article.
  4. Using scan tool, select the DTC display function for the ECM and TCM. Does scan tool display any DTCs? If yes, go to next step. If no, go to step  9.
  5. With scan tool, select Captured Info in order to store the powertrain DTC information. When complete, go to next step.
  6. Does scan tool display DTCs which begin with a "U"? If yes, go to appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. If no, go to next step.
  7. Does scan tool display DTCs P0601, P0602, P0603, P0604 or P0606? If yes, go to DTC P0601-P0607, P1600, P1621, P1627, P1680, P1681, P1683 & P2610: ECM MEMORY . If no, go to next step.
  8. Does scan tool display DTCs P0560, P0562, P0563, P0625, P0626, P2500 or P2501? If yes, see appropriate GENERATORS & REGULATORS article in ELECTRICAL. If no, see DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  9. Is customer's concern with the automatic transmission? If yes, see appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. If no, go to next step.
  10. Is customer's concern with the Inspection/Maintenance (I/M) testing? If yes, go to INSPECTION/MAINTENANCE SYSTEM CHECK  under INSPECTION/MAINTENANCE PROCEDURES. If no, go to next step.
  11. Diagnose by symptom. See SYMPTOMS in TROUBLE SHOOTING - NO CODES - 3.2L CTS article. If no problem is found, go to INTERMITTENT CONDITIONS .
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