Trouble Shooter

Motor,  Apr 2006  by Seyfert, Karl

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Owners of older vehicles may prefer cost-effective solutions when electronic suspension systems quit working. Some OE manufacturers are happy to oblige.

Rough Riding Caddies

Cadillac models from the early to mid-'90s are equipped with speed sensitive suspensions (SSS), and are prone to display the "Service Ride Control" message on the driver information center. I have worked on several of these vehicles, and they all seemed to have a 1039 diagnostic trouble code, indicating an instrument cluster/speed sensor problem. I found an online Cadillac owners' forum and it looks like many owners are having this or similar problems. I recall reading something about disabling the suspension system to correct this. Is there a better solution to this problem than simply turning the system off?

Chet Ladyga

Millville, NJ

It is possible to diagnose these systems, but you'll need the necessary service information to get the job done. Code 1039 is an SSS signal fault, indicating only that there's a problem with the system. The system has the ability to store several additional fault codes, which identify problems in specific areas and components of the system. These codes can be retrieved manually, or with a scan tool and the necessary software. We don't have the space here to cover the entire diagnostic process for each of these diagnostic codes, and refer you to your service information source.

A word of caution here. If you do decide to follow the diagnostic procedures outlined in the service information, your investigation may lead you to one or more faulty electronic struts. These parts are very expensive, when they're available, and they may cause the vehicles owner to throw up his hands in dismay. It's a pretty tough job to get the owner of a vehicle that's at least 10 years old excited about spending thousands of dollars on it, even if it is a Cadillac. The electronic gizmos that were so appealing to the vehicle s first owner may not hold much allure for its second (or third) owner.

There's a less expensive solution to SSS problems, and it's one that's endorsed by the vehicle manufacturer. GM TSB 00-03-11-001, dated August 2000, details the factory-recommended procedures for the installation of "passive" struts to take the place of the original "active" electronic struts. The bulletin covers the procedures for several Cadillac models, as well as several Oldsmobiles, Buicks and Pontiacs from the same era. Refer to the bulletin for the complete list.

According to GM, installation of passive shocks/struts will result in handling characteristics equal to a like vehicle without the computer-controlled ride, with all other components such as tires, tire pressure, springs, etc., being equal. Installing four new passive struts will not extinguish the "Service Ride Control" message, however. If desired by the customer, the service indicator may be disabled after the installation of the four new passive struts, using the service procedures listed below. GM does not authorize this procedure unless four new passive struts have been installed on the vehicle. In other words, don't disable the monitoring system if the vehicle still has the original electronic struts in place.

Once the passive struts have been installed, the wiring harness going to each strut and/or shock assembly must be cut and taped, both under the hood and under the vehicle. What follows is a summary of the additional procedures for specific Cadillac models. Procedures for the other GM models are similar, and are covered in the bulletin.

For 1989-92 Allante models with Speed Dependent Damping (SDD), adjust the BCM override value "BS08." To do this, use the Warmer and Cooler buttons on the climate control driver information center (CCDIC) to decrease the BCM override value "BS08," which is displayed when you enter the system, by 2. When the desired number is displayed on the CCDIC, it must be stored by holding the Elapsed Time and Fuel Used buttons until the new value flashes on and off. When it flashes on and off, the new value has been stored.

For 1991 Eldorado and Seville models with Computer Command Ride (CCR), set the BCM override value "BS09" to O by using the Wanner and Cooler buttons. Store this value by pressing the Econ button on the Climate Control Panel and the Instant Econ button on the Fuel Data/Driver Information Center for about five seconds. The new value will be stored even though the indicator does not flash.

Remove the key from the ignition, then disconnect both battery cables. When both cables have been disconnected, touch the ends of the cables together and hold for five seconds. This will discharge the capacitors in the system and allow the system to perform properly when the battery cables are reconnected. Advise the customer he'll have to reset all radio stations and the clock.

For 1992 Eldorado and Seville models with SSS, observe and record the IPC override "IS08" displayed value. Use the climate control Cooler button to decrease the value displayed for "IS08" by 8. To store the new value, press and hold the Econ and Front Defrost buttons until the new value flashes on and off.