CLARIFICATION ON (RWAL) TROUBLE CODES. GMC Truck S15 Pickup - 4WD 1988

For 1990-2009 cars

# CLARIFICATION ON (RWAL) TROUBLE CODES

SOME CONFUSION MAY EXIST ABOUT HOW TO READ THE TROUBLE CODES FOR THE RWAL SYSTEM ON THE MODELS LISTED ABOVE.

AFTER GROUNDING DIAGNOSTIC TERMINAL "H" TO "A", THE BRAKE LIGHT WILL BEGIN ITS FLASHING SEQUENCE.

#### IMPORTANT: THE BRAKE LIGHT MUST BE ON BEFORE GROUNDING "H" TO "A". IF THE BRAKE LIGHT IS NOT ON, AND TERMINAL "H" IS GROUNDED TO "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. THIS SEQUENCE WILL REPEAT AS LONG AS TERMINAL "H" IS GROUNDED TO "A".

#### 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 * *********************************************************************

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.

COPYRIGHT 1989 GMC TRUCK DIVISION, GENERAL MOTORS CORPORATION. ALL RIGHTS RESERVED.