Testing & Diagnosis: Notes

WARNING: This page does not describe the selected car, but rather 151 other vehicles, including the 1992 GMC Yukon, 1992 GMC Vandura Special, 1992 GMC Vandura, 1992 GMC Suburban, and 1992 GMC Sonoma. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Ensure brake warning light is on before trying to retrieve trouble code. If light is not on, grounding ALDL connector will lead to false CODE 9.

System can be diagnosed through trouble codes. To activate trouble codes, connect a jumper wire between terminals "A" and "H" on ALDL connector and observe flashing on brake warning light. Sequence should be one long flash followed by short flashes (i.e. one long flash followed by 4 short flashes indicates CODE 5).
System will repeat code as long as ALDL connector is grounded. Long flash after short flashes indicates repeat of code. If there is more than one failure, only the first failure code will be stored and displayed. See TROUBLE SHOOTING CHARTS .
On C and K Series trucks with dual rear wheels, a "chirping" noise may occur when applying brakes. This is a mechanical problem, not RWAL. To correct, remove brake drums and spray two coats of Graphite Compound (12345268) onto brake linings. Allow compound to dry between coats.

NOTE: If ECU connector retaining clip is broken when unplugging connector, service clips are available from manufacturer.