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Retrieving Codes

NOTE: Perform procedures for appropriate FUNCTIONAL TEST under TROUBLE SHOOTING CHARTS .
  1. If using Tech 1 for retrieving codes, go to step 3). If using ANTI-LOCK light for retrieving codes, turn ignition on. Using a jumper wire, connect terminal "H" to terminal "A" in Data Link Connector (DLC). See Fig 1. System will repeat trouble code(s) as long as DLC terminals are connected.
    NOTE: The DLC may also be referred to as the Assembly Line Data Link (ALDL) connector. These 2 terms may be used interchangeably.
  2. Trouble codes will be displayed by a flashing ANTI-LOCK warning light. As an example, Code 25 would be displayed by ANTI-LOCK warning light flashing 2 times, followed by a pause, then flashing 5 more times. See 4WAL FAULT CODES  table for diagnosis. If no fault codes are present, see 4WAL SYMPTOM DIAGNOSIS  table.
  3. Turn ignition off. Connect Tech 1 to DLC. Access 4WAL brake trouble codes using Tech 1. Repair trouble codes in order they appear. See 4WAL FAULT CODES  table for diagnosis. If no fault codes are present, see 4WAL SYMPTOM DIAGNOSIS  table.
Fig 1: Identifying DLC Terminals
G90H06369Courtesy of GENERAL MOTORS CORP.
4WAL SYMPTOM DIAGNOSIS

Symptom See
Functional Test
2WD Figure
4WD Figure
ANTI-LOCK Light On Figure
ANTI-LOCK Light Off (1) Figure
Brake Pedal Pulses (1) Figure
Wheel Pull During Hard Braking (1) Figure
(1) These conditions must exist with no fault codes stored
4WAL FAULT CODES

DTC See
21 Figure
22 Figure
23 Figure
25 Figure
26 Figure
27 Figure
29 Figure
35 Figure
36 Figure
37 Figure
38 Figure
41-54 Figure
65 Or 66 Figure
67 Or 68 Figure
71-74 Figure
81 Figure
86 Figure
88 Figure