My 2001 Saab 95’s engine periodically downshifts. Usually the downshift happens after some highway acceleration. The ABS light turns on at the same time as the downshift. The road conditions are always dry. The downshifting started last summer and has continued during the winter months. The alternator was recently replaced but the downshifting periodically continues. MY Saab repair shop cannot figure out what the issue is. Any thoughts?
Sounds like it must be some kind of speed sensor problem. I don’t know the transmission or ABS system on this car. However, both the transmission and ABS system rely on speed sensors to control what they do. You should have a speed sensor on each wheel for the ABS and then a speed sensor or two attached to the transmission.
Have there been error codes that have been pulled from the ABS system/engine computer? Do you also get a check engine light? If your Saab shop is not scanning for codes then its time to find another shop - might be time for a second look anyway.
The Saab shop is scanning for codes. There are none. No check engine light. I have changed shops…to one that only works on Saabs. The owner says he has never serviced a car with this specific problem. Other drivers in the family have had the same experiences with the ABS light and engine downshifting…so it is not my driving! Any other thoughts?
Regardless of anything else this is still most likely to be a speed sensor problem.
So you have now been to 2 shops. What - exactly - have these two shops done? Have they mentioned speed sensors? Have they checked the speed sensors and their circuits? Does their scanning equipment pull history codes or are they just using a generic code reader? Have they put it on a scantool and driven it?
Yes they have driven it. The old shop mechanic experienced the downshift. The new shop mechanic has not. I believe they are obtaining the history code. I will ask about the speed sensors.