For 1990-2009 cars

# ANTI-LOCK BRAKE SYSTEM (ABS) LIGHT ON

#### SUBJECT: ANTI-LOCK BRAKE SYSTEM (ABS) LIGHT ON - DIAGNOSTIC TROUBLE CODES (DTC'S) 42 AND 86 SET (REPLACE HYDRAULIC MODULATOR)

#### MODELS: 1993-95 BUICK SKYLARK 1993-95 CHEVROLET BERETTA, CORSICA, CAVALIER 1993-95 OLDSMOBILE ACHIEVA 1993-95 PONTIAC GRAND AM 1993-94 PONTIAC SUNBIRD 1995 PONTIAC SUNFIRE

#### CONDITION:

SOME OWNERS MAY COMMENT THAT THE ANTI-LOCK BRAKE SYSTEM (ABS) LIGHT REMAINS ON. DIAGNOSTIC TROUBLE CODES (DTC'S) 42 AND 86 WILL BE SET. DTC'S WILL USUALLY SET 5 TO 8 DRIVE CYCLES IN A ROW AND THEN BECOME HISTORY CODES.

#### CAUSE:

DTC'S WILL BE SET DUE TO A MOMENTARY DELAY WITHIN THE ABS HYDRAULIC MODULATOR.

#### CORRECTION:

#### IMPORTANT: IF DTC 42 IS CURRENT DTC, THE DIAGNOSTIC TROUBLE TREE IN SECTION 5E1 OF THE SERVICE MANUAL WILL LEAD TO REPLACEMENT OF THE MOTOR PACK. IF THE FOLLOWING DIAGNOSIS DOES NOT LEAD TO REPLACEMENT OF THE HYDRAULIC MODULATOR, THEN THE MOTOR PACK SHOULD BE REPLACED.

DIAGNOSIS -

- IF DTC 42 HAS SET 10 OR LESS DRIVE CYCLES AND IS NO LONGER A CURRENT CODE (ABS NOT OPERATING, ABS INDICATOR OFF), REPLACE THE HYDRAULIC MODULATOR.

- IF DTC IS CURRENT, CYCLE THE SYSTEM BY STARTING THE ENGINE WITH YOUR FOOT OFF THE BRAKE PEDAL. IF THE ABS INDICATOR REMAINS ON, TURN THE IGNITION OFF AND REPEAT THE PROCEDURE. IF WITHIN 10 CYCLES THE ABS INDICATOR IS OFF AND THE CODE IS NO LONGER CURRENT, REPLACE THE HYDRAULIC MODULATOR.

- IF THE ABOVE DIAGNOSIS DOES NOT LEAD TO REPLACEMENT OF THE MODULATOR, FOLLOW DTC 42 TROUBLE TREE IN SECTION 5E1 OF THE SERVICE MANUAL.

REPAIR PROCEDURE -

IF THE CONDITION IS CONFIRMED THROUGH THE ABOVE DIAGNOSIS, THE HYDRAULIC MODULATOR MUST BE REPLACED, P/N 18023364. THIS IS A NEW PART NUMBER THAT HAS BEEN RELEASED. DO NOT USE PREVIOUSLY RELEASED HYDRAULIC MODULATOR PART NUMBERS. REFER TO SECTION 5E1 OF THE SERVICE MANUAL FOR HYDRAULIC MODULATOR REPLACEMENT PROCEDURE.

PARTS ARE CURRENTLY AVAILABLE FROM GMSPO.

#### WARRANTY INFORMATION:

FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR OPERATION NUMBER: H2518 USE PUBLISHED LABOR OPERATION TIME.

FIGURES: 0 ATTACHMENTS: 0

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 1995 GENERAL MOTORS CORPORATION. ALL RIGHTS RESERVED.