SPEED DEPENDENT DAMPING SUSPENSION SYSTEM UPDATE

VEHICLES AFFECTED: 89-90 V

Product Information Feedback:

In order to gain a better understanding of Speed Dependent Damping (SDD) system problems, all cases must be reported to the Cadillac Technical Assistance Centre. CANSPO has been instructed not to ship parts until they have received authorization that a TAS case has been opened. Dealers attempting to order parts will receive an answer back to "call Technical Assistance Centre ". This program will remain in effect for the remainder of the 1989 and 1990 model years.

1990 System Changes:

The Speed Dependent Damping system will undergo some minor changes for the 1990 model year. The electronic module will be recalibrated to shift to the normal mode at 65 km/h instead of 40 km/h as in 1989. However, the 1990 module will be used to service 1989 cars. Therefore, if a 1989 Allante has a module replaced, the speed at which the struts cycle from comfort to normal will be higher. This change will probably not be distinguished by the owner.

Also, the strut connectors will use a different type of seal to better protect against water intrusion. The 1989 connectors used an O-ring with a plastic backup washer. The 1990 connectors will use a three-ribbed peripheral seal similar to the seals used in weatherpak connectors. The connector body remains unchanged, but due to the larger diameter of the three-ribbed seal, the inside diameter of the strut tenon is larger. The 1990 Allante will use a gas charged strut with different valving, therefore, 1989 and 1990 SDD struts are not interchangeable.

System Check:

Prior to performing any Speed Dependent Damping system diagnosis, the "SDD System Check" should be done. This simply involves reading codes, driving the car over 25 km/h to clear codes, and reading codes again. This procedure will distinguish any current vs. history codes. It will also aid in finding the condition if multiple codes exist.

Multiple Codes:

Multiple codes may set on the Speed Dependent Damping system if the 5 volt feedback circuit sees voltage above 5 volts. Any combination or all of the position error codes (13, 14, 15, and/or 16) as well as code 7 may set if this occurs.

This condition may occur in several ways. If the strut ground circuit is open, voltage from the drive circuit will flow through the actuator and back to the module through the 5 volt feedback circuit. A second method would be if the feedback circuit is shorted directly to battery voltage. Third, if the strut connector is not sealed properly, water may get into the strut tenon and create an electrical path from the drive circuit to feedback.

To diagnose this condition and find the strut connection that may be causing the problem, follow the "System Check" procedure in the Service Information Manual.

Position Error Trouble Trees:

The Position Error Trouble Trees (codes 13, 14, 15, and 16) have been revised in the Final Edition of the 1989 Allante Service Information Manual. This change was made because the current draw of some test lights may be great enough to result in erroneous diagnosis. For this reason, a high impedance voltmeter (i.e., Kent-Moore tool number J-34029-A) is necessary for proper diagnosis.

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.