LEMON Manuals: Even more car manuals for everyone
Home >> Pontiac >> 1987 >> Grand Prix LE, 5.0 H >> Repair and Diagnosis >> Engine Performance >> System >> 4.3L TBI Tests W/Codes >> Basic Diagnostic Procedure

Basic Diagnostic Procedure

NOTE: Most computerized engine control problems are the result of mechanical breakdowns, poor electrical connections or damaged vacuum hoses. Before considering the computer system as a possible cause of problems, ignition high tension wires, fuel supply, electrical connections and vacuum hoses should be checked. Failure to do so may result in lost diagnostic time.

Diagnosis of the computerized engine control system should be performed in the following order:

  1. Make sure that all engine systems not related to the computer system are operating properly. Do not proceed with testing unless all other problems have been repaired.
  2. Perform appropriate DIAGNOSTIC CIRCUIT CHECK for that system. If trouble codes were displayed (other than Code 12), decide whether codes are "hard" or "intermittent" trouble codes. "Hard" codes will cause the "SERVICE ENGINE SOON" light to illuminate continuously while engine is running. See ECM TROUBLE CODE DEFINITIONS table in this article.
  3. If no trouble codes were displayed, proceed to appropriate FIELD SERVICE MODE CHECK.
  4. If no trouble is indicated by the FIELD SERVICE MODE CHECK procedures and/or a driveability problem exists, refer to TROUBLE SHOOTING in the CEC TESTS W/O CODES article in the ENGINE PERFORMANCE section and/or SCAN TESTER USAGE in this article. Comments there will send you to the proper component charts or tell you the most likely system/component to check.
  5. After any repairs are made, clear any trouble codes and perform the FIELD SERVICE MODE check again.
scientia non olet · About LEMON Manuals