Diagnostic Aids

If Tech 1 scan tester cannot communicate with ACM, check Data Link Connector (DLC) for open ground circuit. Check DLC terminals for tightness and good connection. Check Tech 1 scan tester connector pins for damage. Verify Tech 1 scan tester operates properly by using it on another vehicle. Check ABS ground and communication from DLC.

Fig 1: CODE I Schematic

Courtesy of GENERAL MOTORS CORP.

Fig 2: CODE I Flow Chart

Courtesy of GENERAL MOTORS CORP.