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Diagnostic Procedures

NOTE: DO NOT perform this test if no driveability condition exists.
NOTE: Search for applicable bulletins before proceeding with the diagnosis.
NOTE: DO NOT turn OFF ignition when performing this diagnostic test procedure.
NOTE: DO NOT clear the DTCs unless the diagnostic instructs you to do so.
NOTE: If there is a condition with the starter system, diagnose starter system. See appropriate STARTERS article in STARTING & CHARGING SYSTEMS.
NOTE: Ensure battery is fully charged and cables are clean and tight.
NOTE: Ensure PCM grounds are clean, tight, and in proper location.
  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. NOTE: If using a Tech 2 scan tool, obtain the information using the Class 2 Message Monitor feature.
  2. Turn ignition on, with engine off. Using scan tool, attempt to establish communication with the Body Control Module (BCM), Electronic Brake Control Module (EBCM), Instrument Panel Cluster (IPC), Powertrain Control Module (PCM) and Sensing and Diagnostic Module (SDM). Does scan tool communicate with all the control modules? If yes, go to next step. If no, perform SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE 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 HARD START in appropriate TROUBLE SHOOTING - NO CODES article.
  4. Using scan tool, select the DTC display function for the BCM, EBCM, IPC, PCM, SDM and VTD. 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 SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. If no, go to next step.
  7. Were any of PCM DTCs P0601, P0602 or P1621 set? If yes, go to DTC P0601-P0607, P1600, P1621, P1627, P1680, P1681 OR P1683: CONTROL MODULE READ ONLY MEMORY . If no, go to next step.
  8. Does scan tool display DTC P0562, P0563, P0621 or P0622? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  9. Is customer's concern with the transmission? If yes, see appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS or MANUAL 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. Check for the following symptoms: Hard start, surges/chuggles, lack of power, sluggishness/sponginess, detonation/spark knock, hesitation, sag, stumble, cuts out, misses, poor fuel economy, poor fuel fill quality, rough idle, unstable idle, incorrect idle, stalling, dieseling, run-on, backfire, Malfunction Indicator Light (MIL) inoperative, or MIL always on. Did you find and correct the condition? If yes, system is okay. If no, problem is intermittent. See INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
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