Brakes - Clarification On ABS Trouble Codes

89chevy07

GMC NUMBER: 89-T45


GROUP: 5 - Brakes

DATE: April, 1989


CORPORATE
NUMBER: 965006
SUBJECT: CLARIFICATION ON REAR WHEEL ANTI-LOCK (RWAL) TROUBLE CODES

MODELS: 1988-89C/K AND 1989 S/T AND M-VANS
Some confusion may exist about how to read the trouble codes for the RWAL system on the models listed above. After grounding diagnostic terminal ""A", the brake light will begin its flashing sequence.

IMPORTANT: The brake light must be on before grounding "A". If the brake light is not on, and terminal "H" is ground "A", you will induce a false Code 9 in the system.
The following is an example of how to read a Code 4:
Begin the count with the long flash. Continue counting the next three short flashes. The next flash will be a long flash which starts the sequence over again.

IMPORTANT: Sometimes the first count sequence will be incomplete. However, subsequent counts will be accurate.

EXAMPLE: CODE 4

FIRST LONG SHORT SHORT SHORT LONG SHORT
FLASH FLASH FLASH FLASH FLASH FLASH

1 2 3 4 1 2

START END START