Mechanics

SATURN SW1 WHEEL PROBLEM

1997 Saturn SW1 • 90,000 miles

My 1997 Saturn Wagon is having a problem involving the anti-lock brakes. Example: On a dry flat road when you attempt to stop at a stop sign or stop light the anti-lock brakes engage. This is while going slow, even when I coast slowly and then brake. The car acts exactly like it thinks its sliding on a snowy road. The brake pedal pulses like it does when the anti-locks brakes engage - you brake, it un-brakes, then brakes.

I have checked the brake fluid - it's fine. I haven't checked fuses yet.

As far as I can find online and in my car manual it's probably a problem with the wheel speed sensors.

Thoughts?
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Guest
October 29, 2012.



If you had a issue with the speed sensor you would have a code. Have you had the abs computer scanned for codes yet?

Saturntech9
Oct 29, 2012.
Yup. Brake fluid and fuses aren't the cause. If a fuse was blown the yellow warning light would be on and the system would stop working.

GM has had a huge problem with front wheel bearings. They develop a little play, which is entirely normal and common but the design of the speed sensors is such that they just barely provide enough of a signal for the computer to read. The slop in the bearing causes that signal to drop out enough that the computer doesn't read it and thinks that wheel is skidding. That play in the bearings can occur in as little as 15,000 miles. The dealer's scrap metal bin is full of old bearing assemblies.

As far as the computer knows, it is reacting to a normal condition, meaning skidding, so there is no defect and no diagnostic fault code will be set. To find if only one bearing is causing the problem you have to do a test drive with a scanner connected that can display live data, then you watch which wheel speed goes to "0 mph" too soon.

Be aware too, for the benefit of others researching this problem, that there is always a long list of conditions that must be met to set a diagnostic fault code and some of those conditions are that certain other codes can't already be in memory. For example, the ABS Computer compares all of the individual wheel speeds to each other. If there is a code set for the right front, for example, it has nothing reliable to compare to the left front sensor so no code will be set for the left one if the signal disappears, (Note that loss of signal from a weak magnetic pulse is totally different than loss of that signal from a break in one of the wires which WILL still be detected). Not detecting a second problem is a big source of frustration for mechanics and customers. This can happen on other brands of cars too but it's more common on GM front-wheel-drive cars right now because of the very common wheel bearing issue. If you get the first problem fixed right away, it's usually fine until the next problem occurs. It's when you ignore the first problem for many weeks or months, then there's time for a second problem to occur, but it is likely to not set a second code so no one will know about it. Your mechanic will read the codes, diagnose the wheel bearing needs to be replaced, and give you an estimate for the repair cost. It isn't until those repairs are completed and he goes on a test drive that the next code shows up and the warning light is on again, or in your case the system is false-activating yet. Now he has to re-diagnose his work, then tell you more parts and labor are needed. You blame him for not diagnosing it right the first time, but he had no way of knowing that a second problem existed.

Caradiodoc
Oct 29, 2012.
Alright lets not lump this model into gms hugh problem because in my over 16yrs of saturn dealer career I havent seen the hugh issue with wheel bearings on this model. They do fail more often where they use salt on the roads
But hugh problem I would say no.

Saturntech9
Oct 29, 2012.
I have a 1999 saturn SL2 I have over 228,000 miles onmine and have changed one rear wheel bearing when the car had over 200,000 miles on it in all those miles. The most common reason for the rear wheel bearing to fail early on those is people hitting curbs etc.

Saturntech9
Oct 29, 2012.
You're right. I looked up the bearing and it is indeed different. I have a former student who works at the local Saturn dealership and he was bringing me a bunch of the common-failure bearings with the sensor pressed onto the back. Up here in road salt country that bearing typically costs around $100.00 with the ABS sensor, and the same bearing without the sensor for non-ABS-equipped cars costs about 50 bucks more. Why is that? When we have a car with a noisy bearing that doesn't have ABS, we either pop that sensor off or just don't connect it. Those bearings work perfectly and often still look like new, but they caused false activation on the cars they were removed from. The only time you can not find a pile of these bearings in the dealers' scrap metal bins is after they were just emptied.

When we order a new bearing locally for a car without ABS we always tell the parts people the car DOES have it. That bearing with the sensor saves our customers around $50.00.

To my knowledge, no other manufacturer has so many different designs in production or has so many common problems. By "common", I mean every car of that model will develop the same problems sooner or later, and we've seen so many that with a good description of the symptoms we already know what the likely fix is going to be. When you look at GM's very nice older HEI distributors, and their generators, you see that they like large self-contained assemblies. They go together faster on the assembly line, and when the cars using them are relatively new and mechanics have no experience yet working on them, unit replacement is easier than diagnosing and fixing the problem like we do on other brands. I suspect they are no different when it comes to wheel bearing assemblies. You only need one person on the assembly line to install the bearing, and no second person to install the wheel speed sensor. Makes sense to want to save money, but when they used the same design sensors pushed into the spindles that other manufacturers use, they didn't have any more problems than owners of those other brands. Once in a while we'll hear about a Ford truck with false activation, but other than that, when someone has that complaint, we ask them "which year and model GM product do you have?"

Once you autopsy one of these ABS sensors, the cause of the signal dropouts is pretty obvious. While other manufacturers use tone rings with very substantial teeth about 3/16" tall to disturb the magnetic field and create the pulse of voltage, these are flat metal bands with tiny dents stamped into them. It's surprising they work as well as they do.

Caradiodoc
Oct 30, 2012.
They must have a scam going on up there I just checked auto zone for the rear hub assembly for the S models which wilol fit 1991-2002 S models so every year made. The duralast or the timkin hub assembley is more for the abs one also checked rock auto. Com same thing the abs hubs are more then the non abs ones. When the saturn dealers were still open and I worked there the abs hubs were always more at the dealer. Even when I worked at the saturn in upstate ny they still were more. The front bearings on those dont matter because the bearings are pressed in and the sensor is mounted to the knuckleThe S model saturn engine and transmissions were designed and built just for those cars. Also the front and rear wheel bearings dont fit any other car but them. Most the parts on the S model saturns are like that. So I call that model saturn the non gm saturn in 2000 when the L model saturns that all changed. That was a opel model and gm took over control of saturn and it was no longer a different kind of car different kind of company. Like they oringal ads and solgans were there were gm parts alternator batterys radios the gm kiss so to speak. But as far as the core of the car it was all saturn those are my fondest memories of all the years of working for saturn is the years before gm took over. It was so unlike any other gm or other car company out there. We had higher customer satisfaction then mercedes bmw jag lexus etc. As far as abs issues on the saturn s model there were few it was a good system there was a bad abs computer here and there but that was rare. Not many bad wheel speed sensors etheir.I think one of the most common things I can think of was the gears on the abs motor packs would loosen up and set codes get noisey etc. Overal it was a really good system the salt destroys wheel bearings though. In socal they last a longtime usually.

Saturntech9
Oct 30, 2012.