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Diagnostic Procedures

NOTE: Do not perform this diagnostic if there is not a driveability concern, unless another procedure directs you to this diagnostic. Before you proceed with diagnosis, search for applicable service bulletins. Unless a diagnostic procedure instructs you, do NOT clear the DTCs. If there is a condition with the starting system, see appropriate STARTERS article in STARTING & CHARGING SYSTEMS. Ensure the battery has a full charge. Ensure the battery cables are clean and tight. Ensure the PCM grounds are clean, tight, and in the correct location.
  1. Install a scan tool. Does the scan tool turn ON? If yes, go to next step. If no, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
  2. Turn ON the ignition, with the engine OFF. Attempt to establish communication with the listed control modules. If you are using a Tech 2, obtain the information using the Class 2 Message Monitor feature:
    • PCM.
    • Vehicle Theft Deterrent (VTD).
    • Instrument Panel (IP) cluster.
    • Electronic Brake Control Module (EBCM).

    Does the scan tool communicate with all the listed control modules? If yes, go to next step. If no, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.

  3. Attempt to start the engine. Does the engine start and idle? If yes, go to next step. If no, see ENGINE CRANKS BUT DOES NOT RUN in appropriate TROUBLE SHOOTING - NO CODES article.
  4. Select the DTC display function for the following control modules: PCM, VTD, IP Cluster and EBCM. Does the scan tool display any DTCs? If yes, go to next step. If no, go to step  9.
  5. With a scan tool, select Captured Info in order to store the powertrain DTC information. When complete, go to next step.
  6. Does the scan tool display DTCs which begin with a "U"? If yes, see appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. If no, go to next step.
  7. Does the scan tool display DTC P0601 or P0602? If yes, see DTC P0601-P0607, P1600, P1621, P1627, P1680, P1681 & P1683: PCM MEMORY  under DIAGNOSTIC TESTS. If no, go to next step.
  8. Does the scan tool display DTC P0560 or P0620? If yes, see appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS. If no, see DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  9. Is the customer's concern with the automatic transmission? If yes, see appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. If no, go to next step.
  10. Is the customer's concern with Inspection and Maintenance (I/M) testing? If yes, see INSPECTION/MAINTENANCE SYSTEM CHECK  under INSPECTION/MAINTENANCE PROCEDURES.
  11. Review 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, unstable, or incorrect idle and stalling, dieseling, run-on and backfire. See appropriate TROUBLE SHOOTING - NO CODES article. Did you find and correct the condition? If yes, system is okay. If no, see INTERMITTENT CONDITIONS .
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