Retrieving Codes (Non-Scan)

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. Most ALDL connectors are located under dash on driver's side of vehicle. For exact location of ALDL, see appropriate COMPONENT LOCATIONS illustration in SYSTEM/COMP TESTS article. Turn ignition on. 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. Codes will not flash if this is done. See FIELD SERVICE MODE in BASIC TESTING article.

Fig 1: ALDL Connector Terminal Identification
Courtesy of GENERAL MOTORS CORP.
SERVICE ENGINE SOON light should begin to flash codes. Each code will be repeated 3 times. If codes are not flashed, perform DIAGNOSTIC CIRCUIT CHECK in BASIC TESTING article. To exit diagnostic mode, turn ignition off and remove jumper wire from ALDL connector.