2000 Buick Park Ave ABS

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#1
I own a 2000 Buick Park Avenue, 3. 8 L. engine, not supercharged. Illuminated on the dash are: traction control off, ABS and Brake.
All three lights came on one evening when I started the car and did not go out. None of the lights were on prior to parking the car and turning off the ignition.
I checked both front hubs with a multimeter when turning each rotor by hand and I am getting 3-4 Milivolts when turning the rotor. I checked the wiring and have found no breaks or chafed insulation. Last spring I replaced the driver's side front hub, if this information helps. I checked the brake pad condition and have more than half of the pad thickness left. The master cylinder reservoir is nearly full.
I am at a loss as to where to check from here. I do not have an OBD II code checker and Advanced Auto does not have the capability to check ABS brake codes with their unit. Is there an electronic module that can be checked and replaced or do I have to buy the whole ABS unit? I'll bet GM will be proud of the price they get for one.


Rich, East PA
 

nickb2

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#2
Sounds like a fuse shorted out on you buddy. Did you check? Do you hear the abs module activating at key on? Had a few of those abs units back in the day that had a gear in the unit unscrewing and therefore could no longer actuate. Best bet is to erase the codes if not already done and go from there. Salt water sprayed on wiring at bearing connecters often finds a faulty insulated wire. Check your resistances to. Also look for corrosion at abs module for little green stuff. :ROFL
 
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#3
Nick,
I don't recall ever hearing it activate at "key on". I always hear the fuel pump though, even though it is quiet. I'll have to listen for it. I'll also check for a blown fuse.
Thanks for your reply.

Rich
 

Gus

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#4
The EBCM continuously checks the speed of each wheel in order to determine if any wheel is beginning to slip. If a wheel slip tendency is detected, the EBCM commands appropriate valve positions in order to modulate brake fluid pressure in some or all of the hydraulic circuits. This prevents wheel slip and provides optimum braking. The EBCM continues to control pressure in individual hydraulic circuits until a slipping tendency is no longer present. If the EBCM detects an error, the EBCM can perform the following actions:

• Disable the dynamic rear proportioning (DRP)

• Disable the antilock braking system (ABS)

• Disable the traction control system (TCS)

• Disable the vehicle stability enhancement system (VSES)

• Turn ON the ABS, the TRACTION OFF, or red BRAKE indicators on the instrument cluster

• Turn ON the SERVICE STABILITY SYSTEM or TRACTION CONTROL SYSTEM ACTIVE message on the DIC



You need to check what the ABS code is, to narrow down the diagnosis....
 
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#5
Typically the way ABS diagnoses the system is to first run a passive test to make sure everything is connected, by getting a list of your error codes, that tells you what is tested like the four wheel sensors, eight modulating valves, fluid level switch, pump motor, main and pump relays, power fuses, can be up to four such fuses. If all is okay, the main power relay is energized to power up the system, this in turn switches off the ABS light. If the light stays on during the passive test, one of these components is either opened or shorted.

Electronically doing the passive test is easy, just hit each component with a sample current if the results are zero volts, it's shorted, if 5 volts, it's open, looking for a voltage somewhere in between. If not in between set an error code, and read it with a scanner, if you have one. This does not tell exactly where the problem is, for example a wheel sensor can be open or shorted that means replacing it, but can also be the wiring between that component and the ABS computer and that requires crawling all over the vehicle to find it. Without a scanner, an ohmmeter can be used and the best point to test is at the ABS computer connector itself. Some vehicles are easy, others, you have to stand on your head when the computer is buried under the dash someplace.

The computer itself only looks as far as that big fat connector for either an open or a short, but that open or short can be between that connector and anywhere in the vehicle to the source, sure helps to have a manual to find where are these things are hidden, but wheel sensors are at the wheels, but how those wheel sensors are routed to the computer is a mystery for one example especially when you have another zillion cables all over the place. But taking the readings at the ABS connector and knowing which pin numbers are for what is important to knowing which component is the culprit. Then having an idea what the appropriate resistance readings should be.

But this only takes care of the passive check, if the passive check is good, then power is applied to the ABS system, a second dynamic test is made once the vehicle is in motion. In this case the ABS light will go out if the passive test is good, but will come on again if the feedback voltages are not correct. One common error code is caused by having a near flat tire.

Since the 80's ABS as well as other systems have been complicated with flashram, very similar to those memory modules used in a digital camera, you can pull that memory chip and it still retains it's data, electrons are trapped in a gate regardless of whether the chip is powered or not. Unlike the older ram that will lose all data once power is removed, so disconnecting the battery no longer works in resetting the codes. Some force you to have a scanner as the only means to reset the codes, others let you manual reset the codes with a jumper lead to the diagnostic connector. Meaning you have to know your system. Still others are self correcting once the problem has been found and repaired. All depends upon how nasty and what kind of mood the software designer was in when he did the programming.

At first, only error codes were store in flashram, but since OBD II the entire operating system, the program was been stored in flashram, that is also subject to corruption, I am shaking my head on this. But makes it easy for the auto companies to change the OS if they find a goof and goofs are more prevalent as it can be easily changes with the proper equipment, at first very esoteric, but available now if you have the money to subscribe to it, not very practical for just one vehicle. In other words, the system can check out okay, but you have a corrupted program that has to be reflashed, visit your dealer or be prepared to spend about 5,000 to 7,000 bucks to DIY.

For whatever reason, aftermarket scanner manufacturers do not want the liability to show ABS codes. The exact reason for this is nebulous as if the ABS is not working, at least in theory, normal braking is suppose to resume. Seems like the real liability with brakes is doing a brake job itself and forgetting to bled or put fluid back in the system as one example. Accelerating to 90 mph then hitting a tree because you don't have brakes. Now that is where the liability should be at.

One case I recall is where a guy had a small shop to a brake job on a motorhome incorrectly, guy gets in his motorhome, can't stop for a train, catches his bumper and smashes his RV into a phone booth in front of the train station. Who got sued for this? AT&T for putting that phone booth there, they are the only ones that had any money.
 
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#6
Gus and Nick,
Again, thank you for your replies.
I'll check fuses and for "little green stuff" at the connectors. If I find nothing, I'll take it to a dealer to have them check it out. I will not be able to check it out today.

Rich
 

Russ

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#7
Monroe muffler, midas and similar brake shops can do a scan for you. i had mine in for tires and asked them to scanit. They did it free of charge. My guess, you have over 100k on it. If you replaced left front last year, then I bet its your right front or possibly a rear. These things make it to around 120k and crap out. Then every year and a half, they go again. i am in upstate NY in the rust belt, so thats why I figure the replacements dont last. we have torqued them properly, always used a torque wrench and according to the parts houses and other shops, they all experience the same thing. GM makes replacement harness's for the fronts. Sometimes the wires are rotten inside and there's no wire left. A simple scan is the place to start.
 
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#8
Interesting about Midas, daughter had a brake job warrantied for life, so she went back with a small service charge that equaled more the price of buying new pads and rotors, plus they did a terrible job of cleaning the parts that caused a dragging pad so I put on new rotors and pads cleaning off all the rust first, those brakes lasted her a long time.

Another daughter went in for a wheel alignment when I advised her to do so with a RWD cars, the naughty guys loosened her front wheel bearings and scared the hell out of her saying her wheels would fall off, same thing happened to my two sons, were told they needed new ball joints, when we just installed new ball joints. Those I went to, refused to give me the estimate. A friend went to a tire dealer with ABS light on, was given a quote for $960.00, asked him if he had a flat tire recently, he said, now that you mentioned it, that light came on at the same time. His ABS needed to be manually reset, took all of 30 seconds with a jumper lead on his 95 GM SUV.

Glad you had positive experiences with brake and tire dealers, but I can't share those happy experiences, can list a lot more problems, but just replying and not writing a book on this subject.