INTERMITT. RED 'BRAKE' LIGHT ABS CODE IS MAY BE PRESENT

MODELS AFFECTED: 1987-1989 ALLANTES

Some 1987-1989 Allantes may set an ABS code 15 intermittently, usually on the first brake apply after the vehicle has not been used for a period of time (i.e., overnight). When the ABS code 15 is set, owners will observe that the red "BRAKE" warning light will turn on. Since ABS codes are erased when the ignition is turned to "OFF", no codes may be found when the vehicle is in for service; and the condition may be difficult to duplicate.

During brake apply, code 15 will set if the EBCM receives a signal that the hydraulic unit control pressure switch opens before the brake light switch closes. The proper sequence is for the brake light switch activation to be recognized by the EBCM before the pressure switch activation. Therefore, a misadjusted brake switch may cause code 15 to set.

An intermittent code 15 may set due to a "sticking" control pressure switch when the pedal is released. In this case, the brake light switch opens and the control pressure switch remains open (or "stuck") longer than it should. When the EBCM recognizes that the control pressure switch is activated and there is no brake switch input, code 15 will set.

This condition may be detected by performing the "Hydraulic Plausibility Switch Tests" using the J-36210 ABS tester outlined in the Service Information Manual. When the pedal is released, the control pressure switch (S1) LED will remain illuminated and the brake light switch (BLS) LED will be off. If this observation is detected, the control pressure switch is suspected of sticking and requires replacement.

When a condition of intermittent setting of an ABS code 15 is suspected, use the following procedure:

1. Verify proper brake switch adjustment by pulling brake pedal against internal pedal stop. Switch will be moved in retainer providing proper adjustment. Refer to Service Bulletin T-89-92.

2. Clear the ABS code 15 and evaluate for resetting of ABS code 15.

3. If ABS code 15 resets, replace the pressure switch.

For warranty purposes use labor Operation H-2494 at .5 hour for pressure switch replacement or H0770 at .2 hour for brake switch adjustment.

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.