1994 Buick Roadmaster BaseFACTORY OEM SERVICE PROCEDURE

Code 68, A/C Relay Circuit Shorted

When PCM detects A/C has been requested, PCM will activate A/C clutch relay. When relay is activated, voltage should be present at both A/C compressor clutch and A/C clutch status terminal at PCM. If PCM detects voltage on A/C status line when A/C has not been commanded on, Code 68 will set. A short to voltage anywhere on A/C status line, or stuck relay contacts, will set Code 68. When Code 68 is set, PCM does not turn on SERVICE ENGINE SOON light.

NOTE: Test numbers refer to numbers on diagnostic chart.
  1. Code 68 sets if voltage is detected on A/C status line for more than 20 seconds after PCM has disengaged A/C relay.
  2. This step will isolate ignition feed portion of circuit from clutch circuit.
  3. If Code 68 reappears at this step, PCM is internally shorted to voltage.
Fig 1: Code 68 Schematic (5.7L) A/C Relay Circuit Shorted
G94A37150
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Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
  • β€’ You are missing required tools, torque specs, or safe lifting equipment.
  • β€’ You are not confident in the next step or safety outcome.