ABS problem *solved* bad VSS

[MyWhiteKnight]

Split topic and edited title-HJ

Hello Everyone

Sorry it's been so long, single parenthood keeps CC tweaking to a minimum, so I usually just read a few posts with nothing to say. I have the ZR2-PA3 wheels on my CC. Picked them up at ebay for $128.50 + $60.00 shipping. The AR aftermarkets required more polishing than I had the time for, and I was able to sell them to a friend quickly. First drive after installing the PA3's, the ABS dash light was intermittently coming on. When the light was on, the ABS seemed to work opposite of what it was supposed to. When I was slowly coasting to a stop, ABS kicked in and I would end up in the middle of the intersection! Since I don't like ABS anyway, I just pulled the fuse for it. That may have been fine as a temporary fix.

Recently, after the CC was warmed up, and I got a couple of miles down the road, the speedometer was jumping back and forth from the then present speed to zero, and while it was doing this it felt as though the tranny was slipping in and out of neutral. I could put the pedal to the metal, and everything was fine......that was then.

Now, when it does the jumping, it seems the tranny disengages and the speedometer stays at zero, even while rolling along. I have to stop the CC, manually put it in 1st gear and limp home in 2nd. 3rd and overdrive acts like neutral, and reverse is fine.

The ZR2 wheels do appear to make the CC stand a little taller. I don't know why, they are 15x7, just like stock, offset may be different though. I'm still using the stock Goodyear tires, CC is my weekend cruiser with only 10, 500 miles on it. It's good that I don't need it everyday, because I'm presently not driving it in this condition.

My nephew does body work at the local Chevy dealership. He says the PA3 wheels should not have needed a speedometer calibration, and I may be correct in thinking that pulling the ABS fuse wasn't wise as a permanent fix. He is thinking that I need to have the computer cleared and reset, at this stage. He said the dealership service dude with the programmer is a buddy of his, and he would ask him to bring it over to my place. I was hoping that was going to be last night, no show.

[killian96ss]

MyWhiteKnight, the different rims have absolutely nothing to do with your tranny and ABS problem especially if your are using the same tires. Also, your truck should not sit any higher with ZR2 rims if your are using the same tires that were on your stock rims. Maybe I am missing something?

Steve

[MyWhiteKnight]

killian96ss, Thank you for responding. I totally agree, and no you didn't miss anything. The appearence of the truck sitting a little higher with the ZR2 wheels, may be an optical illusion created by the different style rims. I didn't take before and after measurements, but a friend did ask if I cranked the T bars, I didn't.

Yes, I am using the same tires, and did not experience any of the previously mentioned problems before I changed to the ZR2 wheels, this is all I know for sure. The lugs were torqued to the specs of 100 lb-ft (140 N-m).

The ABS (brakes), the transmission shifting and the speedometer, commonly share the speed sensor on the transfer case (VSS). The powertrain control module uses the VSS to shift. I personally do not understand why these things went haywire after changing the rims. If anyone has any thoughts on this, I sure would appreciate your sharing. I still haven't heard from the guy with the programmer.

[04crewvt]

When you were changing the rims did you fiddle with the brakes at all? It might be possible that you pinched a ABS sensor wire and it may be shorting out. Not a sure bet but it might be a possible place to start.

[Snoman002]

I agree on the wires.

Pull the front tires and check the wires, for a start.

It's probably that one thing is not related to the other, it just happened to be related. Just had this happen to me as a matter-of-fact, and although the system was the same between the problem and the work I did, the problem was not related to what I had done.

Other than design, and maybe a little weight, there is absolutly no difference in your old wheels and the new ones.

[MyWhiteKnight]

Hello 04crewvt and Snoman002,

I sure am grateful for your suggestions. I checked the front wheel sensors and wires, when the ABS light first began to glow. Haven't fiddled with the brakes, other than inspecting them when the wheels were off. Everything appeared as it should be. The only other thing I've noticed unusual is that I needed to add a quart of tranny fluid. Couldn't see any leaks by looking, so I slid some cardboard underneath, immediately after the last time I drove it. Nothing is on the cardboard, but.....

The guy with the Tech2, says that one of the rear wheel speed sensors is working sporadically, and the other rear wheel sensor is not being detected by the programmer. It also seems limp home mode caused the tranny fluid to get a little too hot . Hopefully a fluid and filter change will be all the tranny needs. The Tech2 is not showing any error codes Snoman you may just have the right idea with the problem being related, but not connected. The dealer service dude says he suspects the VSS or a connector.

The mechanic says we can use a dealer stall, to get under it. He says if I can be patient, we can do it during off-business hours and save some cash by avoiding some shop and labor charges. We have to wait our turn and they work overtime too. Good thing I have the patience and another ride

[04crewvt]

Bad wheel sensors are a problem with some GM products, There was a recall on full size pickups for corrosion of the sensors that led to a problem similar if not identical to this. My dad's full size had this happen and he nearly ran my brother over while moving a trailer. It took three visits to the dealership to argue that even though his was not a vehicle covered by the recall the problem was the same. If they do the work make sure the change the sensors out completely not just cleaning and inspecting them. When my dad's truck was fixed he drove no more the 30 yards before the problem was back, one sensor was replaced and the other was just cleaned. He pulled back into the lot and demanded that either the dealer replace the sensor or stand in front of their work (literally)while he drove toward them at full speed and hit the brakes (they replaced the sensor). I have not heard the crews having this problem but I will bet the same sensors are used in our trucks as the fullsize and we may just be seeing the effects in our rigs now. We should all keep an eye out for this problem and if it starts showing up report it immediately to GM.

[MyWhiteKnight]

04crewvt, You are correct about "Bad wheel sensors are a problem with some GM products". There IS a TSB on front sensors for 15 models, 1995 to 2003, including mine and other forum members:

Brakes - Low Speed (Below 5 MPH) ABS Activation

Bulletin No.: 02-05-25-006B

Date: January 05, 2006

TECHNICAL

Subject:
Antilock Brake (ABS) Activation At Low Speeds (Clean Wheel Speed Sensor Mounting Surface)

Models:
1999-2000 Cadillac Escalade
1995-1999 Chevrolet Silverado (Old Style)
1995-2000 Chevrolet Suburban, Tahoe (Old Style)
1995-2003 Chevrolet Astro Van, Blazer, S10
1995-1999 GMC Sierra (Old Style)
1995-2000 GMC Yukon, Yukon XL (Old Style)
1995-2001 GMC Envoy, Jimmy
1995-2003 GMC Safari Van, Sonoma
1995-2001 Oldsmobile Bravada

Cause

The cause of this condition may be an increased air gap between the wheel speed sensor and the hub reluctor ring due to rust and debris built up on the sensor mounting surface.



The TSB correction, in so many words, is to clean and relube the sensors. Vehicles with low miles or still in warranty should not be experiencing rust and debris build up Didn't they charge us extra for rust prevention? What debris, I haven't driven it enough to get weeds wrapped around the axles!? The sad part with my situation is, my front sensors seem fine at the moment, and I'm past the 3 year warranty It really does not make sense that a truck with so few miles would suddenly begin to show so many problems. But if I were to take this up with GM, their argument would be "not driven enough". They use the "not driven enough" routine so much it has been given a name, they call it "Lot Rot". Well, if I drove it right now, I would ruin the tranny and get broadsided at the first intersection, then it would surly rot at the junk yard

I wish I could do away with ABS, not an option. The speedometer flux and tranny limp home mode, are electronically connected to the ABS and vehicle speed sensor. Malfunction of ABS will disable dynamic rear proportioning, which turns on the instrument panel red brake light. DRP is for pressure balance control of the hydraulic system, and is a function of the ABS Modulator. Geez, and I thought modern technology was good!? I think this may be too much of a good thing

[MyWhiteKnight]

Well, it seems all the problems were due to a bad Vehicle Speed Sensor (VSS). Had nothing to do with the ZR2 wheels, nor putting them on.

So, yes it was related, but had nothing to do with anything I did. So, if anyone has ABS activation at low speeds, and/or speedometer flux, and tranny limp home mode, and you already checked your wheel sensors as ok, change the VSS. My tranny and everything else is fine and the crew is running as good as before the problems started.

The guy at the parts department said they have been selling lots of them

[04crewvt]

Glad to hear you got it straightened out.

[HenryJ]

Thanks for finding the solution and posting the result That is sure to help someone else some day.

[MyWhiteKnight]

I sure appreciate everyone's thoughts on this one. It was a hard nut to crack. Limp home mode, and the threat of a blown transmisson had me pretty freaked out, so I hope my comments and solution will save someone some aggravation.

[Horsehammerr]

What is the part number on our VSS.

[MyWhiteKnight]

I looked in all my old receipts and I'm sorry to say that I can't locate that part number. Maybe a Chevy or GM dealership parts department can help you.

[HenryJ]

rockauto.com can be a good source for part numbers sometimes.

[Horsehammerr]

Besides throwing ABS & Brake warning can a bad VSS also trigger CEL ? I can't find any thing wrong with my front speed sensors . My ABS & Brake warning come on sometimes at startup other times while driving . Either time simply turning off the ignition and restarting at startup, or switching the key off for a second and back on while driving cancels the warning. The CEL only happens rarely. Then I do the battery disconnect routine. And yes thank you Brule, Rockauto does have the part #s.

[Horsehammerr]

Checked with code reader and had zero codes. With CEL or ABS & Brake warning. I wonder how that can be ?

[HenryJ]

Erratic problems can sometimes show up from something as simple as a loose battery cable. Check those connections. Just a shot in the dark.

[Horsehammerr]

Will do a total check on all connections. Thanks ! I hadn't thought of that.

[Horsehammerr]

Just had a "FLASH". My positive side on my battery will not screw in completely tight without feeling like it might stripout if I tighten it down even a slight bit more. Any idea how I could fix this problem ?

[HenryJ]

Shorter bolt, or add a washer. Clean it all up and add some terminal treatment to slow down any corrosion. I use fluid film. It stays liquid and gooey

[Horsehammerr]

I had a lite coat of silicon on the terminal bolt and cleaned it off with carb cleaner. I then screwed the bolt in to find that it felt pretty lose in the threads. The new bolt is ,I believe, metric and smaller than the ?american standard threads in the battery post hole. Got a like size AS bolt and it fits perfect. Oh well, so much for cheap *ss chinese replacement parts. I'll see if I can find a Quality terminal bolt.

[MyWhiteKnight]

My problems only occured while in motion "warmed up", never at start up. I can't remember if the CEL came on with the ABS warning light, sorry. In the early stages of the VSS failing (before tranny started going into limp home mode), "I could put the pedal to the metal, and everything was fine", for a day to a few days. My CrewCab wasn't showing any codes neither.

I agree with HenryJ, maybe something is loose. Let us know if a tighter terminal bolt is the answer, and I hope it stays that simple. It took me 2 months to figure out it was the VSS, it was just like Snowman002 said, "It's probably that one thing is not related to the other, it just happened to be related. Just had this happen to me as a matter-of-fact, and although the system was the same between the problem and the work I did, the problem was not related to what I had done. "

[Horsehammerr]

Well I've tried to fit a tighter bolt but, i think the only way is to drill and tap a new mounting hole . I'm just not sure if that can be done to a battery. It's more of an irritation than anything. The ABS and brake systems both function perfectly but, my mine won't relax when that ABS & Brake warning light keeps popping on.