: Is there a way to test for a bad wheel speed sensor? Car is braking on its own.



Josh D. Nooney
07-22-11, 05:51 PM
The issue I am having is that on occasion I get a "stability sys active" message on the DIC and the car brakes on it's own. It is usually the passenger side front wheel that brakes. I had to pull into the suicide lane one time because the car wouldn't quit braking on its own. This message is usually accompanied by the ABS light coming on. I am assuming this is a wheel speed sensor issue. Is this sensor and the ABS sensor one in the same? Is there a way I can test these sensors with a mutli-meter? Is there anything else I should be looking for when I take the wheel off. The inner edge of both my front tires are very worn (previous owner), could this be the cause? I am in the process of getting new front tires. I have HPtuners software but I don't think it will read non-ECM codes such as the ABS sensors.

The car is a 2006 STS V8 1SG with the Magnetic ride and N87 staggered wheels.

ddalder
07-22-11, 06:54 PM
There are a couple of things you can do...

Unplug the suspected bad WSS, connect a volt meter set for AC volts across the two WSS terminals and spin the hub. If any signal is being generated, you'll see a reading in millivolts on the meter. The problem is that this won't likely help in diagnosing an intermittent sensor, only when the sensor is completely inoperative (which doesn't sound like your situation).

The best way is to use the proper scan tool. You can not only check for codes, but you can also watch in real time as the vehicle is being driven. The scan tool will show you how fast the computer believes each wheel is turning. Between this, and reading codes, it will help you diagnose which corner of the car the problem is in. It may also be a wiring problem, but it is more common for the problem to be the sensor in the hub assembly.

Josh D. Nooney
07-22-11, 07:29 PM
Thank you for your reply. Is the wheel speed sensor the same as the ABS sensor, or are they two separate sensors?

ddalder
07-22-11, 07:36 PM
Yes, they are the same. Wheel Speed Sensor is a "more correct" term because the signal it provides is used for more that the anti-lock braking functions.

EChas3
07-22-11, 07:47 PM
In my opinion, this is a dangerous condition. If you aren't experienced in ABS/active brake systems, you should drive slowly to the nearest shop and let them fix it.

Josh D. Nooney
07-24-11, 12:32 PM
I am assuming that I need a Tech 2 to read ABS/Stability control codes? I can't find where my HPtuners will read any non-ECM information on my STS. Can someone confirm what the correct hub assembly part # is. I think it is 513186, however all the websites list that part as being only for "base model" STS. I am pretty sure my car has the performance package. Thanks for the help.

ddalder
07-24-11, 12:47 PM
I use a Tech2, but many different scan tools may be able to read the codes (Snap-On, etc). The STS-V and, if I'm not misktaken, the STS with the performance package have a 6 bolt wheel (others here may be able to confirm this) whereas the base STS has a 5 bolt wheel. GM part numbers are almost always 8 digits so that number doesn't look right. Front and rear hubs are not the same. Left to right is, but you'll need to be certain which is at fault to get the right one. Changing a hub isn't usually difficult (unless it's corroded in place), but without proper diagnostic tools, you may want to have a shop help you with this.

Josh D. Nooney
07-26-11, 10:08 AM
I have found a few scanners that will read ABS codes so I will probably pick one up in the next week or so and add that to my growing collection of diagnostic tools. The number I posted above for the hub is the Timken part # as well as some other replacment parts manufacturer's part #. I don't know what the GM part number for the hub is.

I took the hub out Friday night and it wasn't difficult at all. Once I retrieve the codes I should be able to fix it fairly easily. I am going to replace the front tires and get an alignment first to see if that helps the situation. The tires are extremely worn on the inner edge from the previous owner.

Here's another question... My ABS light is not currently on and neither is any of the stability control error messages. Will the ABS code scanner show me pending and history codes similar to how the ECM shows codes that have not activitated the MIL?

ddalder
07-26-11, 11:26 PM
I don't think replacing your front tires and an alignment will help with this problem, although it sounds like you may need to do this for other reasons.

As for the code scanner, I can't speak for all of them, but I know the Tech2 will. I frequently scan vehicles that have codes (both current and history) with no MIL illuminated. The Tech2 will show each code, whether it is current or history, whether that particular code requested the MIL, whether the last test passed or failed and in many cases, the number of ignition cycles since the test last failed. Again, not sure about different brands/models. I would look at a couple and if you have any questions, visit the manufacturers site, call their support line or contact the authorized reseller. These will be your best source of information.

Josh D. Nooney
07-27-11, 12:04 AM
Supposedly the Actron CP9580 will do ABS codes. It's funny that I have the software and cable to tune my Cadillac but I am going to have to buy a new scan tool just to read ABS codes. I assume that the "service stability sys" message on my DIC will show up on my search for ABS codes, or is this another module altogether.

ddalder, thanks for all your help and advice!

ddalder
07-27-11, 12:17 AM
You're welcome. The ABS/TCS/VSES (Antilock Braking System/Traction Control System/Vehicle Stability Enhancement System (StabiliTrak)) all relate to the Electronic Brake Control Module (EBCM).

porkfarm
07-27-11, 08:38 AM
Did somebody rotate your staggered tires for you ? I would also use one of those laser temp units.. You know, point and shoot, take a temp tool.. After a drive, do all four rotors and see if one is a lot hotter than the other side.. Take the tire off and give a look see.. Maybe a loose connection, mouse chew, rock or stick stuck, sticky caliper.. If all else fails, to the stealer it is.. ( never a one stop for me.. always have to bring it in twice... yeah, we ordered the part.. )

BaTu
07-27-11, 10:27 AM
I have found a few scanners that will read ABS codes so I will probably pick one up in the next week or so and add that to my growing collection of diagnostic tools.

Consider the AutoEnginuity. With the "Enhanced GM Package", it will do 95% of the Tech-II plus, with additional Packages has the ability to perform the majority of the Ford, Chrysler, Asian, German, etc. factory diagnosis tools too ;)

Josh D. Nooney
07-27-11, 11:06 PM
Nobody rotated the tires for me. It has the 235's on the front and 255's on the back. I have only had the car a couple of months. The only thing I have done is change the front brake pads and replaced the differential mount.

I now have the "service stability sys" message on all the time. I will purchase an ABS capable scanner here very soon and get this straightened out. Are the front wheel speed sensors usually the ones that go bad?

porkfarm
07-28-11, 07:05 AM
My car is a 2005 with 80K and I have done the pads & rotors once, never had a problem with the sensors and we have lots of salt on the roads in winter. I do take the the tires off once a year and lube up the caliper pins so the brakes release fully.. Maybe with the new pads you put on, the thickness is an issue ? Just thinking out loud here.

I notice that I coast better after the pads wear in a bit.

You might need to use a scanner to clear the codes now that one came up. Yes a good scanner is almost a must have with these cars.

Josh D. Nooney
07-28-11, 10:51 PM
Porkfarm,

I have considered that the brake pad change might have tirggered the issue since it never really happened until after the pad change. However, I put very few miles on the car prior to the pad change. The pads I took off the car very well might have been the OE pads. One thing that I noticed when I changed the pads on this car was how easy it was to compress the pistons in the calipers. It took little to no force, is that normal. I have checked the fluid and everything appears normal. Thanks for everyone's help.

ddalder
07-28-11, 11:24 PM
Wheel speed sensors are contained entirely within the wheel hub assembly. They are not dependent on any external input except power supplied by the EBCM. Brake pads, wheels, wheel offset and wheel rotation have no effect on the WSS functioning correctly.

Josh D. Nooney
08-02-11, 12:01 AM
I had the codes read today by a friend of a friend. The service stability light wasn't on when I had these scanned so I believe they were all history or pending. Here is what we found:

C0045-0F - Left Rear wheel speed sensor malfunctioning
C0045-00 - Left Rear wheel speed sensor malfunctioning
C0196-1A - Yaw Sensor Code????
C0253-00 - Steering wheel centering error?

I couldn't find much on the C0196 and the C0253 codes other than one being the yaw sensor and the other being the steering wheel sensor. I am going to start by replacing the left rear wheel speed sensor and see what happens. They are cheap online so I will start there. Just wanted to let everyone know what the codes were. It is funny that I suspected the front right wheel speed sensor since that always seems to be the wheel that brakes on its own, but it makes sense that the left rear wheel is the one that is malfunctioning, causing the front right to brake (opposite wheel).

ddalder
08-02-11, 03:28 AM
The last two digits of the DTC is the symptom code.

C0045-00 is LR WSS Circuit, No Additional Information
C0045-0F is LR WSS Circuit, Signal Erratic

Something is clearly intermittent.

C0196-1A is The Yaw Rate combination bias exceeds 5.7 degrees/second

C0253-00 Centering Error.
To set the DTC, the vehicle must be driven for 10 minutes without completing steer angle centering.

The last two codes can be caused by various problems and can both be set because of a common component failure however, I would definitely start with the WSS and work from there.

Josh D. Nooney
08-02-11, 03:25 PM
On the "centering error" I assume that is the steering wheel sensor. The car was just aligned over the weekend but the steering wheel is still just slightly off center to maintain a straight path. How sensitive is this sensor? Could being just a hair off center trigger this message? I am going to have a new WSS by next week and see if I can't get all these codes to go away after I replace the left rear.

ddalder
08-02-11, 03:34 PM
The steering wheel position sensor is fairly sensitive. The problem may well be the non-centered steering wheel. The car will monitor the position of the wheel and compare with data received from the yaw rate sensor and lateral accelerometer. When this isn't consistent, you can generate a system fault. Definitely have the steering wheel properly centred before looking at other faulty components. This is cited as one of the causes for setting C0253.

Josh D. Nooney
08-03-11, 12:49 PM
Thanks ddalder!

Josh D. Nooney
08-04-11, 09:20 PM
Can you guys tell me what the size of the axle nut is? I did a search and found a post that listed it as both a 35mm bolt and 36mm bolt. Can anyone confirm the correct size.

AllGoNShow
08-06-11, 10:55 PM
Can you guys tell me what the size of the axle nut is? I did a search and found a post that listed it as both a 35mm bolt and 36mm bolt. Can anyone confirm the correct size.

Just did my right rear thanks the ddalder's scanner :) Problem all fixed. Axle nut is a 35mm I believe, I had a friend pop by with his set but he has them all shaved down for clearance on some of his toys haha so the numbers were missing. I think a 36 "might" hold it but torquing with it or rounding the head's won't be fun.

Josh D. Nooney
08-07-11, 12:11 AM
Thanks. The reason I ask is that there is thread from about 7 months ago where they list it as both a 36mm and a 35mm. Then today when I was looking at new ones online, they list the replacement nut as a 34mm. Harbor Freight has a set of several axle nut sockets for cheap so I will probably pick those up. My new hub showed up today. I noticed something wrong as soon as I opened the box, so I re-checked the part number. Turns out the place I ordered it from sent me one for a Ford Five Hundred by mistake. The part numbers were only 1 digit off. So much for tackling this job this weekend!

Josh D. Nooney
08-24-11, 11:16 PM
To update everyone... I put a new LR wheel speed sensor on two weeks ago. Since then the car has still applied the brakes to the right front tire. It has done it about three times. Clearly, I didn't fix the problem completely. However, since the wheel speed sensor was changed I have not seen any of the DIC messages that I used to get with almost every ignition cycle. I feel like I did accomplished something at least. I now think I may have a steering wheel sensor issue (one of the other codes found scanning the ABS module). I have bought a steering wheel sensor but have not installed it yet. I noticed two days ago that when I was sitting at a gas station and moved the steering wheel slightly that the DIC message saying "Stability Sys Not Ready" showed up. I was parked and only moved the wheel so I feel like this might be a good indication that I could have a malfunctioning steering wheel sensor. Tonight I took the front wheels off and did a quick inspection. Nothing was out of the ordinary. I did notice that there seems to be a lot of drag on the front brakes. They will spin but stop quickly and you can hear the pads contacting the rotor. Is this normal. I have also noticed that I seem to have some drag on the brakes when I let off the gas while driving. It reminds me of "hill decent control" that they offer on Jeeps. Do you think this could be related. These days I just turn off the stability system as soon as I get in the car!

Josh

AllGoNShow
08-25-11, 10:35 AM
Front calipers are designed to leave a little bit of pressure on the brake pad so the pad is always in contact with the rotor even without the brake pedal depressed. This makes sure that there is instant response from the brakes when you do push the pedal. Should there be enough drag to stop the wheel from spinning in the air as soon as you let go after a spin? No, possibly a seized caliper or pad guides so I would definitely look into that and make sure your front brakes are ok.

Josh D. Nooney
11-21-11, 06:30 PM
To update everyone and also help any forum member who may have this problem in the future.... The problem turned out to be the steering wheel sensor. I bought the new sensor at my local Cadillac dealership, since the part Autozone has listed will not fit the car (my car at least). The part was less than $90 and I am sure you can find it cheaper online. I pulled the column out of the car and installed the new sensor. I put the sensor in 6months ago and the problem has not returned. I hope this info helps someone in the future. Thanks for everyone's help in diagnosing the issue.