Eremon1

I have a 96 Oldsmobile Cutlass Supreme 3.1 V6 Automatic. Recently had problems with the starter and Vehicle Speed Sensor which have been solved. Since owning this car the 'Low Oil Level' Light and the ABS light have been on. The oil light often goes out after some time driving and the oil level is physically okay on the dipstick. The ABS light came on after a few months of owning it and it used to come and go but now it seems to stay on all the time. Brakes seem ok.

Any ideas?

mack1

Hi Eremon1 and welcome back,

I know nothing at all about oil level sensing. Maybe someone with experience in that area will jump in and help.

I have a 96 S10 blazer and have worked on it's ABS unit. That year, GM was using mostly Kelsey-Hayes ABS systems. Likely yours is that brand. Two wheel sensors and the vehicle speed sensor are used by the unit to know if a wheel(s) is locked and will respond by stopping foot pressure to that wheel(s) and releave pressure to it, thus stopping the locked condition. The most normal failure is one of the sensors, two wheel sensors and the Vehicle Speed sensor. You just replaced the VSS, so we can count that one out. There is three brake fluid pipes from the ABS unit. One for each front wheel and one for both back wheels. The unit can control each front wheel, or both back wheels as needed. (With front wheel drive, yours might be different)

96 was the first year that they passed the wheel speed sensors to the PCM and it sent the signal on to the ABS electronic controller. Prior to 96, the ABS was a "stand alone unit". The PCM also drives the ABS light on the dashboard for the first time. If the lamp is removed from the instrument cluster, the PCM, in it's infinite wisdom, will turn on the brake lamp instead (you won't find that anywere in the books).

Google Kelsey-Hayes to find lots of info on that system.

The wheel sensor are of the magnet/wire wound type similar to the VSS sensor. They look at metal teeth on the inside hub of the wheels. The sensor wires can be easily found entering the hubs.

Check the wheel sensors and let us know what you find.

Very best regards,
Mack1

Eremon1

Okay, this morning while driving I attempted to pass a slow car. When I accelerated to passing speed I noticed a small sound like a bump or something and the engine light came on. After this it was rev-ing real high to get from standing still until I got to about 20Kmph. Then is seemed to shift normally. When I got home I checked the fluid level it seems to be okay. I looked for leaks and saw nothing. After it cooled down it seemed to be working normal. Now when I drive it, it seems normal accept when I try to accelerate too much, then it seems like the tranny is slipping.

I'm no expert, but usually if a clutch or something has gone bad, it stays bad right? Why would this seem to come and go? When I turn on the heater the engine temp comes down a bit and the car doesn't seem to act up as much...

Eremon1

Anybody have any ideas?

Eremon1

Okay scratch the last problem posted. I let the car sit for a day and then drove it again. After about 4Km the engine light went away. I'm driving the car as nicely as I possibly can.

I'll keep you posted on the ABS sensor issue when I get the chance to take a good look at how and exactly where the sensors are located. If it's as easy as the VSS was to change out then I shouldn't have a problem.

Volt-Schwibe

I'm going to say this sounds like a torque converter solenoid has had a problem. It may have become stuck, and sitting unstuck it, but i can't be sure. In those newer cars the torque converter is computer controlled, and when you passed that car, the transmission went through a sequence of adjustments, in the tightness of the converter lock-up state, as well as the sensativity of the shift. So if you had an engine light, as well as something you could hear/feel, followed by the feeling of the transmission slipping, i'm pretty sure this is a torque converter problem. There is a small chance an accumulator piston has failed inside there, causing first gear to slip, especially if it seems to have no problems in any gears other than 1st.

I'd say this one needs a shop, where some guages can be applied to it as it's run through a couple simple tests. Without those guages, there's not alot any mechanic could do, aside from just opening it and checking each part.

mack1

On the ABS issue, there is some more info that I forgot to mention. The light came on when you had problems with the VSS sensor, as it should. It didn't go out when you replaced the sensor. That could be normal, as a scan tool will clear all but the ABS, and the PCM itself will clear the other lights. At dealerships, they have an expensive scan tool that will turn the light off, but they will charge you for that. If there is an actual problem with the ABS, it will come back on.

Your ABS might be functional, even with the light as nothing has extinguished the light.
If ok, but just a light, others have taken their vehicles on a dirt road and done some slide stop menovers that cause the ABS to function. Once it functions, it will clear its own light. It's worth a try.

Best regards,
Mack1

Eremon1

Thank you. That makes sense to me. It went away yesterday while driving and hasn't come back so far. Right now I'm being very easy on it while driving. I've been trying to keep in under 3500 RPMs through the shifts. The car is running fine at the moment. I think you're right, the best thing to do is to have the computer scanned for the codes to help pin-point the problem(s).

@Mack1
The ABS issue was actually a few months before the VSS. During that whole problem I was assuming that the ABS was somehow related, but the light was on months before the VSS failure and is still on now. The brakes seem ok, I don't get any vibrating during normal driving as I would expect. In the winter when I'd hit a patch of ice or something I remember the TRAC light coming on and I'm sure the pedal-vibe was there at that time. I will try the dirt road idea.

Just to make sure I have the idea correct, I basically drive to a speed and then press the brake hard enough to try and lock the tires, while still maintaining control? This should activate the ABS which should then reset the light if it's a false error or old code?

*I forgot to mention* That the ABS light is on when the car starts most of the time. But sometimes it isn't on when the car is started and even for a moment of driving. Same with the oil light, sometimes it's not on at car startup. Usually when it was recently driven tho. And it goes out after some time driving.

mack1

The ABS does a selfcheck when the ignition switch moves from off to on. If all is OK, it turns the lamp off. If it comes on when the car starts moving, it means one of the sensors is not sending signal to the unit. Again the three sensors are on two wheels and the VSS.

In order to test ABS, the sensors have to send abnormal signals to the unit. One or two wheels locked or slow while the other(s) is turning normally, and of course, the break pedal must be pressed (not the park brake). If you lock all four wheels, then you may, or may not get the unit to energize and try to control the brakes.

Best regards,
Mack1

Volt-Schwibe

Usually 25 mph is enough to produce a lock up skid. If you want to try at an even slower speed, try it in a wet parking lot at 15 or 20, or on gravel or dirt. You shouldn't have to slam on the brakes at a crazy high speed, just any speed high enough to cause all 4 wheels to slide. (the skid doesn't even have to last more than a second or two for the brake system to realize it's in a full skid)

But, mash the pedal fairly hard, or you might not get all 4 wheels at the same time.

I've seen people successfully reset their ABS system this way, it is definately something that should be written into the repair manuals.

Eremon1

Also, I'm not having trouble with first gear, it's all the rest of them that sometimes seem to go to sleep along with the speedometer. I just replaced the VSS with a used one from the wrecker and I also have another one. Could it be a faulty VSS or something else?

Okay, the engine light has been off since that one day. The car drives mostly normal if I keep the RMPs down to 2000-2100 Max. When the car warms up if I try to accelerate much faster than that, the speedometer goes funny, sometimes all the way to 0 and the tranny feels like its in neutral. Then if I let off the gas I can sometimes get the speedometer to pop back up and then the car will drive sorta normal, but for the most part once this happens I have to let the car sit for a half hour or more and it is ok again. I was talking to somebody at work about this and they said it could be the trany-filter is clogged.

Could a clogged trany-filter be causing this type of issue?

If so, is this something that can be replaced in the back yard?


Also, regarding the wheel speed sensors. I've been looking around for info as my Haynes manual doesn't seem to cover that info in any detail and I've found conflicting information. Some sources say all four wheels have a speed sensor and others say it's only in the front wheels or back wheels.

Now my question about that is, if my wheel sensors are causing my ABS light to come on, could they also be affecting the transmission in some way?

Eremon1

I also have been doing some reading on the Vacuum Modulator Assembly. Apparently if this fails or there are vacuum line problems then the transmission can exhibit odd behavior including slipping and shifting problems. What are your thoughts on this Mack1?

mack1

Actually, I'm not good with transmission problems and I leave it to others to respond. I've noticed that others have had lots of problems with transmission solenoids, but mostly on Dodges.

Going back to the oil level sensor....Did you mean oil pressure? I recall that oil pressure is required for the PCM to keep the engine running, at least on some later models. I don't know how the PCM would respond to an erratic oil pressure signal. See if you can clear that up and see what else works better. I'm still not convinced that the VSS sensor which measured so close to the original one was the total fix for your first problem. I like sensors that measure bad if they are bad, or at least some distance from norm.

Best regards,
Mack1

edited...I'm thinking of an oil pressure switch, not pressure sensor.

Eremon1

Fair enough on the transmission. I think I should start a transmission thread because for now this issue is more important to fix than the ABS or Oil light problems which seem to be sensor issues.

For the oil, it's simply a light called Low Oil Level. But I've checked, checked and rechecked the oil and the levels are fine. I've heard other say this happens commonly after oil changes but I'm not familiar enough with the sensor system there. I believe it's located somewhere in the oil pan but I haven't taken it apart. I'm not a fan of playing around with gaskets unless I really have to. I've also heard some things said about the low oil level indicator pointing to a bad oil pump. Any thoughts?

As for the VSS. I hear what you're saying, but I've got three of them and the one bad one and they all seem to measure about the same. Perhaps the methods of testing I've used don't produce accurate results.

Volt-Schwibe

I'm starting to think that these problems are all relating to the ECM module.

1. You have a speedometer problem, anytime you attempt to goose it.

2. You have a weird transmission problem, which shows symptoms in parallel with the speedo problem. The ECM controls most of the activities inside the transmission in these newer cars. Because the ECM controls these parts, the problem would seem to be caused by one of these parts, even though that part might be fine.

3. The oil light stays on regardless of actual oil level. This could be related to a bad pump, pushing a low pressure, but that depends on if this vehicle uses pressure to check level, or actual oil level in the pan. (your book should answer that) Alternatively, on these GM cars, especially oldsmobile, a rare issue can happen where the oil doesn't get changed for a 50,000 mile time period, and the oil can gum up certain passageways, causing a low pressure signal to the sending unit. (the test for this is to remove the sending unit, and apply an actual guage, and run the engine to about 2000 rpms in neutral, the fix for it, would probably be a complete tear down and cleaning, or some sort of endoscopic cleaning procedure)

4. The ABS light is on, and as mack1 said, the VSS signals are translated through the ECM module on these years of GM vehicle.

Anyhow, the one thing that connects all these problems is the ECM. Perhaps it's getting poor power signal, or perhaps it's not getting clear signals from all it's remote parts, but it would seem to me that something is seriously wrong here, and the only clear link i see between all these problems is the ECM. Maybe check to see that it's getting strong power, also check ground. Check all your connectors from the ECM all the way to the parts that are misbehaving, and remember, this problem could all be caused by one single connector, because on these ECM controlled vehicles, there's a few sensors that set the bar for the others, so if one sensor isn't working right, then a whole bunch of others will be interpeted incorrectly, seeming like problems with all those parts, when it's one single part that is bad. (or not firmly connected)

It could be that all these problems have simultaneously developed, but it's starting to make me think the ECM is failing.

I wish i could help more, I have a friend i can ask to read over this thread tomorrow, maybe he'll have some insight that i don't.

Eremon1

Okay, I was thinking that is a possibility but the thing that has me confused is the intermittent nature of the problem and how it seems to be around the time the car gets to peak operating temperature. I know there is gunk in the rad when the orange and green types of coolant were mixed at some point. I'm wondering if there is a coolant flow problem to the trany. Also I've been hearing an odd sound coming from the area were the vacuum modulator assembly sits. I've heard that if the VMA fails or doesn't produce the correct vacuum then this can cause the transmission to exhibit odd behaviors in shifting.

If it is the ECM, can I pull and old one from the wrecker and pop in straight in or do I need a scanner to retrain the computer after the ECM swap?

Volt-Schwibe

On something as old as 90's, as long as it had the same engine and transmission, then no retraining would be required.

Also, the coolant does not flow into the transmission, it's the opposite, transmission fluid flows into a tank inside the radiator tanks, and cools down when it contacts the metal, which is contacting the radiator coolant, and then back to the transmission. It's very rare for these lines to get clogged up, so unless something has smashed a line down flat, there shouldn't be any problems there.

Unless it really is a clogged transmission filter, which is pretty easy to replace, but you have to drop the transmission pan down, and replace the filter, along with a new gasket. These bolts are problematic if you overtighten them, as it crushes the gasket. There's not usually anything in the way of the pan, so it's usually pretty easy to get it out.

It shouldn't cost more than about 20$ plus fluid to change it, if you decide to go that direction with it.


On a side note, i could swear that they discontinued the vaccuum accumulator in the mid 80's, in favor of a "TV cable".

if your book says you have a vaccuum accumulator as opposed to a TV cable, then it could be something wrong with the accumulator, although the symptoms don't match up all that well.

Eremon1

Well the transmission fluid looks really clean so I doubt it's the filter after all. But it still couldn't hurt to change it and the fluid anyhow.

As for the vacuum modulator assembly, not accumulator, yes there is in fact one there as it states in my repair manual. And it does affect shifts if it isn't working properly. I just don't know exactly how to go about testing it.

Volt-Schwibe

Because the transmission filter is usually a really fine filter, (5-10 microns) the fluid would always seem very clean, so it's hard to know if the filter is clogged without a pressure test.

As far as adjusting the vacuum modulator, it depends on which transmission you have, but it's normally done with a guage, and then a turn of a screw.

Your book should have a chart showing the different transmission pan shapes, and you should be able to identify which you have from this.

Eremon1

Okay that makes sense. I'll get the trany filter/fluid change just to be sure for that. It's cheap enough.

I have the 4T60-E transmission.