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BASIC DIAGNOSTIC PROCEDURE Oldsmobile Eighty-Eight IX

3.3l/3.8l Pfi Tests W/codes 1 illustration ~375 words

BASIC DIAGNOSTIC PROCEDURE

Note. Most 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»(/oldsmobile/eighty-eight/ix-1986-1991/remont/testing-diagnostics/#33l38l-pfi-tests-wcodes) 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 «STANDARDIZED ECM TROUBLE CODE DEFINITION»(/oldsmobile/eighty-eight/ix-1986-1991/remont/testing-diagnostics/#33l38l-pfi-tests-wcodes) table in this article.
  3. If no trouble codes were displayed, proceed to «FIELD SERVICE MODE CHECK»(/oldsmobile/eighty-eight/ix-1986-1991/remont/testing-diagnostics/#33l38l-pfi-tests-wcodes__field-service-mode-check) for fuel injected systems.
  4. If no trouble is indicated by FIELD SERVICE MODE check and/or a driveability problem exists, refer to SYMPTOM DIAGNOSIS and/or «SCAN TESTER USAGE»(/oldsmobile/eighty-eight/ix-1986-1991/remont/testing-diagnostics/#33l38l-pfi-tests-wcodes__scan-tester-usage) in this article. The 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»(/oldsmobile/eighty-eight/ix-1986-1991/remont/testing-diagnostics/#33l38l-pfi-tests-wcodes__field-service-mode-check) check.

Scheme 1

Scheme 1: ENTERING OR EXITING DIAGNOSTIC MODE (NON-SCAN)
Scheme 1: ENTERING OR EXITING DIAGNOSTIC MODE (NON-SCAN)
  1. Turn ignition on. Do not start engine. "SERVICE ENGINE SOON" light should glow. Locate Assembly Line Data Link (ALDL) connector attached to ECM wiring harness. For exact location of ALDL, see appropriate figure under «COMPONENT LOCATION»(/oldsmobile/eighty-eight/ix-1986-1991/remont/testing-diagnostics/#33l38l-pfi-tests-wcodes) in this article. Insert jumper wire across terminal "B" (diagnostic "test" terminal), and terminal "A" (ground). (Scheme 1) CAUTION: Inserting spade lug (jumper lead) into terminals of ALDL connector grounds ALDL "test" terminal. Do not ground ALDL connector until after ignition is on (engine not running).
  2. "SERVICE ENGINE SOON" light should flash Code 12. Code 12 consists of "FLASH", pause, "FLASH", "FLASH" followed by a longer pause. Code 12 will be repeated 2 more times. If any other trouble codes are stored in ECM memory, they will be displayed in the same manner.
  3. To exit diagnostic mode, turn ignition off and remove jumper wire from ALDL connector.