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Retrieving Codes (Non-Scan)

NOTE: For information on retrieving codes using a "Scan" tester, refer to owners manual supplied with "Scan" tester.
  1. Turn ignition on. DO NOT  start engine. SERVICE ENGINE SOON light should glow. Locate Assembly Line Data Link (ALDL) connector attached to control module wiring harness. Most ALDL connectors are located under dash on driver's side of vehicle. For exact location of ALDL, see appropriate COMPONENT LOCATIONS illustration in the article I - SYSTEM/COMPONENT LOCATIONS in the ENGINE PERFORMANCE section. Turn ignition on with engine not running. Insert jumper wire from terminal "B" (diagnostic test terminal) to terminal "A" (ground) of ALDL connector. See Fig 1 .
    NOTE: Inserting jumper wire into test and ground terminals of ALDL connector with engine running will cause fuel injected vehicles to enter field service mode. Flashes of the SERVICE ENGINE SOON light will not indicate codes if this is done. See FIELD SERVICE MODE in BASIC TESTING article in this section.
    Fig 1: ALDL Connector Terminal Identification
    G90B01199Courtesy of GENERAL MOTORS CORP.
  2. SERVICE ENGINE SOON light should begin to flash codes. Each code will be repeated 3 times. If codes are not flashed or SERVICE ENGINE SOON light does not illuminate, perform DIAGNOSTIC CIRCUIT CHECK in BASIC TESTING article in this section. To exit diagnostic mode, turn ignition off and remove jumper wire from ALDL connector.
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