TeeJay3800 Posted May 30, 2012 Report Posted May 30, 2012 Hey guys, first post in a LONG time! I have a question on my friend's 2007 Grand Prix. I'm not sure on the model, but it's definitely not the GTP since it has the n/a 3800 (it does have leather seats and dual exhaust though). The problem is that the ABS and traction control lights come on often while driving (either saying service those systems soon or that they're disabled). Also, the brake pedal pulsates under braking, making it seem like the ABS system is being activated even though there is no wheel slippage. The wheel bearings were replaced, but the issue is still occurring. I'm assuming the problem is a sensor of some kind, but if you knowledgeable folks could give me some specific information as to the cause, I'd appreciate it! Thanks! Quote
Night Fury Posted May 30, 2012 Report Posted May 30, 2012 Likely a wheel speed sensor, which is integrated into the hub. Hope you have a warranty! Could also be the pigtail to the sensor. Pulsation you are feeling should only be felt under heavy braking and is brake force distribution, something totally different than ABS but feels similar in the pedal. Will work even if ABS is off. Quote
TeeJay3800 Posted May 30, 2012 Author Report Posted May 30, 2012 Thanks for the info. Are you saying the the warnings lights in the dash and ABS system activation (when it shouldn't) couldn't be caused by the same problem? So the ABS/trac lights are caused by the wheel speed sensor, but the pedal pulsation is something different? Quote
Night Fury Posted May 30, 2012 Report Posted May 30, 2012 If the ABS/trac lights are on, both of those systems are deactivated. Any remaining pedal pulsation should be the brake force distribution. Sorry, I should've been more clear. Brake force distribution helps keep any one wheel from taking too much load and locking up, and works even when the ABS is deactivated. It is typically only felt in moderate to heavy braking, for obvious reasons. If it is felt under light braking, you may have additional problems like a sticky caliper or something. Quote
TeeJay3800 Posted May 30, 2012 Author Report Posted May 30, 2012 Awesome, thanks for the detailed info. I haven't actually driven the car, but am going off of their description. I think they said the lights aren't always on, and the pedal pulsation isn't always felt either....both seem to come and go. Assuming only one wheel speed sensor is bad, how much would that be at an average shop? Quote
Night Fury Posted May 30, 2012 Report Posted May 30, 2012 It's integrated into the hub, and the hubs run $80-$100 on Rockauto, so tack on another $20 to that, plus labor.... Prolly $150-$200 Quote
Night Fury Posted May 30, 2012 Report Posted May 30, 2012 And have them scan for the code, who knows, it may be something totally different. But 9 times out of 10, it's a wheel speed sensor or the pigtail to one. Quote
Cutlass350 Posted May 31, 2012 Report Posted May 31, 2012 Bottom line: The ABS codes must be scanned! No ifs, ands, or buts. You can find an ABS scanner for the car for under $100. The pulsing is something else. I do not agree at all that it's the electronic proportioning valve. If someone can feel any pulsing from that, then their ABS module is POS and garbage that is YELLING: "I'M A POS ABOUT TO FAIL -- *REPLACE ME NOW*"!! Also, IMHO, 99% of the time, a pulsing pedal is from a warped rotor, or out of balance wheel. Do you have old, worn, or POS rotors? Was any wheel every put on without a torque wrench? Etc. When the ABS/TC light is on, the ABS and TC functions are fully disabled. The electronic proportioning valve is basically a static value at that point. Bottom line #2: Fix the ABS. Then, concentrate on fixing the pulsing. Good Luck! Quote
Night Fury Posted May 31, 2012 Report Posted May 31, 2012 Above poster.... do you even know what the brake force distribution is? Have you felt it in action? One good point in that post though, is it the typical warped rotor shudder that shudders throughout the car, or is it felt JUST in the pedal, very similar to the ABS engaging? Quote
Cutlass350 Posted May 31, 2012 Report Posted May 31, 2012 Above poster.... do you even know what the brake force distribution is? Have you felt it in action? Yup. I'm curious, what do you think it is, and how it differs from ABS? It's as I said: It's an electronically controlled proportional valve. Also, it is often used as a cheap way to get rid of the proportional valve. So, just because a car has EBD, that does not mean that it really does have a better braking system. It's not "super new". Caddys and truck had similar things back in the 80's. But, back then, it was semi-mechanical in nature, and based on the tilt of body in relationship to the frame. All the "brake force distribution" does is vary the amount of force applied to the rear wheels. How it does that varies a lot - similar to how the different ABS systems are is controlled (like Vette vs cheap GM car). So, again, IMHO, no pulsing should be felt from the EBD. Pulsing in the "proportional force distribution" would be very bad in many ways. Quote
Cutlass350 Posted May 31, 2012 Report Posted May 31, 2012 After a quick search, here's a good example of what it does in general: http://www.toyota.com/safety/star-safety-system/electronic-brake-force-distribution.html As I mentioned, there are a ton of ways that the electronic proportional valve (what it really is, ignoring the marketing BS) is adjusted. Quote
Night Fury Posted May 31, 2012 Report Posted May 31, 2012 Whatever you say, jethro. I guess the question for the OP now is: Is the 'pulsation in the pedal' an actual warped rotor pulsation that also shakes the car, or a pulsation in the pedal alone that feels similar to the ABS activating in 3rd gens? Quote
TeeJay3800 Posted May 31, 2012 Author Report Posted May 31, 2012 Could also be the pigtail to the sensor. Could you explain what you mean by "pigtail"? They mentioned that there appears to be some insulation missing or something to that effect from the wires leading to the wheel hub. I'm thinking that might have something to do with the warning lights. Quote
Breakdown Posted May 31, 2012 Report Posted May 31, 2012 Pigtail is slang for wire with no termination. More often it's used to describe, tearing both the male and female connectors out of scrap cars, and one will have the Pigtails (excess wires) that are simply cut prior to the next connector or terminal point. Unfortunately with the speed sensors on the hubs, they often have a wire come loose and it shuts down the entire ABS because of zero feedback you can try and re-solder, but since the wheel bearings come with the speed sensors, many will just elect to replace the whole thing. The key is getting it scanned so that you know which one may be malfunctioning. Assuming that it's a wheel speed sensor to begin with. Quote
Night Fury Posted May 31, 2012 Report Posted May 31, 2012 Could you explain what you mean by "pigtail"? They mentioned that there appears to be some insulation missing or something to that effect from the wires leading to the wheel hub. I'm thinking that might have something to do with the warning lights. It could be. And by pigtail, that's essentially what I meant. Is the questionable wire on the sensor part or the car end? Quote
Addicted To Boost Posted June 2, 2012 Report Posted June 2, 2012 The BEST way to go about the ABS/Trac lights being on issue would be to go somewhere that has an OBDII/ABS scanner and find out what codes it has. Any o'reillys I've ever been to will let you use their scanner for free. On my 04 GP, my problem turned out to be faulty wiring going to my right front wheel speed sensor. If it is just this wiring pigtail, it's pretty easy to replace and fairly inexpensive. I bought a new pigtail off rockauto for like $25. This is it: DORMAN Part # 970042 ABS Harness http://www.rockauto.com/catalog/moreinfo.php?pk=1821668 You just cut off the old wiring to the wheel speed sensor and splice in the new wiring. Pretty straightforward. I'd be leaning towards the wiring, seeing how both wheel bearings were already replaced. However, get the car scanned to find out what codes it is throwing first. Quote
GP1138 Posted June 4, 2012 Report Posted June 4, 2012 On a completely unrelated note: Hey TeeJay!! Quote
TeeJay3800 Posted June 7, 2012 Author Report Posted June 7, 2012 On a completely unrelated note: Hey TeeJay!! Hey John! Long time no talk. I'm glad to see w-body.com is still such a popular and active community! For anyone interested, it turns out the problem was indeed something with the wiring leading to the wheel speed sensor, rather than the sensor itself. Apparently when the shop replaced the wheel bearing, they damaged the wiring which lead to the abs/trac warning lights. Thanks to all who helped! Quote
Ryebread Posted September 22, 2012 Report Posted September 22, 2012 Chances are its the module going bad. I had the same symptoms with mine. They are very expensive though, but there is a guy that will repair it for around a hundred bucks, he did mine in about a week and everything works perfectly. http://www.cheapabs.com/vrpontiac.html Quote
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