2000 w/155k miles ABS engages when braking and turning left

Just started last night. Coming into a left turn with brakes, the ABS engages (buzzes and I can feel it in the pedal). doesn't do it when braking straight or braking and turning right.

Left front wheel bearing (and ABS sensor) was replaced 2.5 years ago. Right one never done.

I hope to be able to scan it tonight.

Any thoughts?

Thanks..

p.../NH

Since it happens when turning, you most likley have a broken wire in one of the speed sensor harnesses.

ABS light finally came on. It must have taken the ABS out of the circuit because there are no more symptoms. I'm sure there's no ABS functionality either...

Scanned it. 2 codes: C1227 C1234 Left rear wheel issue. Interesting..

Thoughts?

Check the harness connection in the back to the sensor. The one mounted on the trailing arm of the axle, or it may be on the body by the axle, don't remember for sure, lots of problems with those. If all the connections are ok, then probably a problem with the sensor itself.

Yes, it does look like the LR circuit/sensor......could be either .....

If there is no play in the bearing, I'm leaning towards the harness.......one thing you can try, is disconnect the harness at the passthrough connection to the body......now disconnect the harness at the sensor and get a resistance reading...reconnect....now go to the main passthrough connector and connect to the LR circuit with your ohm meter.....resistance should be the same as the sensor.......now start to move and flex the entire length of the harness from the sensor connector to the end.....if you see a fluctuation in the resistance, bad harness.......

Thanks to all for the replies. Forgot to mention, when I scanned it the other night I cleared the codes (and the light).

I got under the car this AM (been away on a trip). I re-seated the front ABS connectors at the wheels. And I re-seated the rears at the body pass through.

Tech II, I didn't see any means of disconnecting the harness/sensors at the rear wheels. Just at the body pass through. It looks like the wires go right through the backing plate. I did follow what I could see of the wiring harnesses, and they looked ok. No chaffing, breaks etc. They are all enclosed in wireloom, and appear to be securely fastened so they don't wiggle.

I drove it a whopping 1 mile to work today, and I am not sure if I heard the ABS pump come on or not (no light). i think I heard it once. I will be driving it a bit more tonight and report back.

Thanks again.

P.../NH

Drove it about 80 miles so far. I can pretty much duplicate the problem. The issue happens only when turning left whether I have my foot on the brake or not.

It sets the same codes C1227 and C1234. Sometimes the ABS light comes on, but it goes out after one or two drive cycles. Bearing is about $85. There is enough wrong with the car at this point that I don't want to put any more $$ into it if I don't have to.

I just want to sell it. Too bad because the engine is strong, uses no oil (I have used synthetic since the first oil change (at mile 3000). I am the first owner.

Gonna check more of the wiring tomorrow. Maybe check the hub too.

P.../NH

Tech II, I didn't see any means of disconnecting the harness/sensors at the rear wheels.


Look again....it's just a two wire connector, just like the front connectors....follow the wire harness all the way to the back of the hub.....

They are hard tp get to because they the back of the hub goes into a "enclosed " area on the axle.

If the bearing assy is from china then this is quite possible the left is bad. when turning left the left wheel rotates slower and less than the right .. this then causes the ABS to come on because the left sensor/bearing being defective creates a very low voltage than the right OEM bearing assy.

I have troubleshooted these issues many times.

what to do is compare the output of the left to that of the right. jack up vehicle and rotate the wheel should get .5volts AC. if lower then thats the problem.

no reason to get new vehicle with small things like this.

these parts are common failure items especially when you purchase chinese bearings..

use timken USA .

Drove it about 80 miles so far. I can pretty much duplicate the problem. The issue happens only when turning left whether I have my foot on the brake or not.

It sets the same codes C1227 and C1234. Sometimes the ABS light comes on, but it goes out after one or two drive cycles. Bearing is about $85. There is enough wrong with the car at this point that I don't want to put any more $$ into it if I don't have to.

I just want to sell it. Too bad because the engine is strong, uses no oil (I have used synthetic since the first oil change (at mile 3000). I am the first owner.

Gonna check more of the wiring tomorrow. Maybe check the hub too.

P.../NH

125.00 for the timken bearing assy 3 yr warr.

Thanks folks.

GMTech... YOU"RE NOT KIDDING !!!! The harness and connector is way up in the inverted "hollow" of the rear axle. Looks like I would have to pull the brakes, slave cyl, backing plate and hub. By that time I may as well replace it.

Couple of added tips. Wife says this happened to her once last Feb on a longer trip. She heard the ABS noise, then after a few times the light came on, then went out shortly thereafter. (Nice time to tell me....5 months later)....

It has gotten worse. So bad now that it happens when driving straight. Foot on or off the pedal. Any slight pressure on the steering wheel to the left, and the ABS motor/pump activates. I have to be going at least like 3-5 mph or so. Anything slower and it doesn't activate.

It's not as bad when I first start out in the AM, but after 10 mins of driving, it's back to the usual. If I was a betting man (even in light of the C1227 and C1234 codes) I'd think shorted wire. It really appears that when ever I turn the wheel to the left even just an inch or two, with hardly any effort, the pump starts.

I can't believe that the small amount of pressure on the steering wheel either changes the LR wheel rotation enough, or unload the bearing enough to change the signal. Then again, I defer to the experts.

J cAT, this is the original bearing. (I bought the car brand new in 2000). 156k on it now. There appears to no radial or axial play in the hub. Smooth rotation, no noise or wobble. When the front left one went, I replaced with Timken. Easy job. I think I posted a DIY here somewhere when I did it.

Jc AT, are you saying the sensor/pickup itself will generate a 1/2 volt simply with wheel rotation? That I can disconnect it at the body passthrough and measure there? Or is there a different place to test at? I've got an oscilloscope. Would I see it with that?

My reason for selling the car is not just this issue. There's other stuff too. This has become a 3rd vehicle for me (I use it to haul bigger items. Now I'll use my small utility trailer). I think it's time has come.

I appreciate all the input. Thanks again.

P.../NH

where the hub sensor wire connects to the car wiring harness this is where you measure the .5 volts ac with the hub rotating at a good amount by hand. this is how I checked out my vehicle which is described in the repair manual. compare the right and left hubs.

sensor failure to output correct voltage may not show as a bearing being worn loose etc...what I did find is the sensor removal and rusted colored grease reveals the cause as to why the sensor cannot produce the correct voltage at the slow speeds. this is because of the seals rusting out which thencauses road salt to enter.

I have ramed into the sensor hole with a grease gun alot of grease. this worked for a month . then I repalced the hub.

using a scope to see the waveform could be used . the waveform is not that important as fast drop outs would not effect the total ave value to cause the pcm to create an abs activation.

on electrical powered vehicles this measurement by a scope is actually needed. too much noise from the electrical powered motors will throw off the abs .

I had a few minutes to burn.

New info. Just scanned the ABS. Found 4 codes; Everything points to the LR except the 1216.

DTC C1216 Brake Control Relay Coil Circuit Open
DTC C1223 LR Wheel Speed Sensor Input Signal is 0
DTC C1227 LR Excessive Wheel Speed Variation
DTC C1234 LR Wheel Speed Circuit Open or Shorted

I still don't understand why you can't disconnect the harness from the hub...it's accessible(you don't have to pull anything apart to get to it)....then you do a resistance check between the end and where it passes through the body at the harness connector......then flex the line to see if the resistance changes......If it does, it's the harness....if it doesn't it's the sensor....

tech II,

Perhaps we are talking about a different style of GM hub/rear end, or maybe I just don't understand.

I am going to try and upload a few pix to show you what *I* am seeing. maybe that will help both of us. Tnx.

For some reason, I don't remember the U-vans being like this.....I worked on Transports/Montanas and the harness was definitely not hard wired to the sensor, and you didn't have to take anything apart.....you show a picture from the rear and bottom...I think you access the connector, looking at it from the front...there has to be an opening in the tube on the front side.....

Well, I just found my manual last night and opened to the pages below. Is this bearing THAT easy to replace? Remove drum, 4 bolts and out?

If so, I may just have a go at it. At first, it looked like I would have to get the giant brake spring off, backing plate, slave cyl etc. (I don't have a tool for the return spring.

But if it's as simple as it looks.... I may just go for it.

P.../NH

Yeah, thats pretty much it. It may be a little stuck in the axle housing though.

What's the best way to get it out? Slidehammer attached to the wheel spindle? Prying? Brute force?

Also, do you think I'll have enough play in the wire to get my hands in and disconnect it?

Tnx

Slide hammer would be good, should have just enough room for the plug in the back of the hub.

Update. Towards the end of this debacle, I had 4 codes set C1216, 1223, 1227, 1234 (x2). The 1216 was a hard code. I would reset the ABS light and within seconds, the 1216 would come back.

I replaced the hub this AM. Took about an hour. I did not have to remove any brake parts. Pretty straight forward. Remove wheel, brake drum, remove four bearing flange bolts, attach small slidehammer to hub. 2-3 very easy taps of the slidehammer and BOTH the hub AND backing plate came off together. Hanging by E brake cable and brake line. Had just enough room to get the ABS connector off. Note: I could not get the connector off via the two access holes provided. They are too small.

A few more hits on the backing plate with a small hammer and the hub popped right off the backing plate.

Cleaned and lubed the bearing surface, connected the ABS, remounted the hub, reset the ABS light, test drove 2 miles. Mission accomplished.

Thanks to all for the help. Here are a few pics.

P.../NH

Glad to hear it! Thanks for the post and pics!