Retrieving Codes (Non-Scan): Notes

Turn ignition on with engine off. 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 and codes will not flash. See FIELD SERVICE MODE in BASIC TESTING article.

Fig 1: Identifying ALDL Diagnostic Connector Terminals
Courtesy of GENERAL MOTORS CORP.
SERVICE ENGINE SOON light should flash codes. Each code is flashed 3 times. If codes DO NOT flash, perform DIAGNOSTIC CIRCUIT CHECK in BASIC TESTING article. To exit diagnostic mode, turn ignition off and remove jumper wire from ALDL connector.