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2005 Buick ABS Brake Light On Intermettently

H

handcannon

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I'm not sure if this is the best place for this as this is dealing with ABS brakes, but since it is not a diesel I guess this will do. If it is OK to be in the brake section then maybe a mod could move it there.

My wife's car, a 2005 Buick Century, has four wheel ABS. It has been intermittently setting the SES and anti-lock brake lights, and recently started setting the emergency brake and low pressure (fluid level is good) brake light. When they come on all I have to do is shut off the car and re-start it and the lights will be off for a while. The intervals between when the lights come on has been getting shorter. My wife has complained also about a "vibration" she occasionally feels. I also felt it just recently, and I'm thinking the ABS pump running is the "vibration".

Today I took the studded tires off, and while doing that I checked the wheel bearings and brake pads. The wheel bearings all turned smooth and had no loose feeling to them. The rear pads are still in good condition, but the front needs to be replaced.

We don't have the funds to take the car to someone else, so I'm the primary mechanic. I have no experience with ABS brakes so I'm just guessing. But, I'm thinking that since the lights are easily shut off just by re-starting the car that the problem centers around one, or more, wheel sensors. I have not tried reading the codes as I don't have a code reader. Sometime this week I'm going to try to meet her in town to see if I can find someone to read codes.

Non-ABS brake work is not difficult for me as I have done all my own brake work for a number of years. I'm just hoping someone on this forum has the experience to walk me through diagnosing and finding the problem with the ABS system.

Don
 
Wheel bearings are tricky to diagnose since they're a sealed unit. You might check all four corners, hoist the car and grab the wheel/tire top/bottom and check for worn bearing type movement.

Its hard to 'feel' any roughness by hand in these when the bearing is not loaded.

I think you can disable the ABS by pulling a fuse, not sure.. Just for diagnosis of course.
 
If it tripped the ses then you should have a code to start with. It's been my experience that the sensors in the hubs are the weak point. The plugs get corroded and/or the sensor in the hub fails way before you can detect any slop in the bearings.

Generally those problems don't trip a ses light though. Just turns on the abs/brake lights
 
Orange lights can be ignored for a time. Red lights mean park it or fix it -- NOW!

It is possible the worn front pad are setting the system off - but that may not be a feature on a GM car.

With a SES and ABS light combo I would start with grounds, esp. the ABS unit ground, and then consider GM has weak ignition switches that will undervolt a computer. Bad battery? You get really weird codes and system failures/errors when the ign switch undervolts a computer. The switch partially burns up and becomes a resistor causing like 7v at the computer. Check ECM system voltage in a scanner and compare to battery voltage.
 
3500GMC said:
Wheel bearings are tricky to diagnose since they're a sealed unit. You might check all four corners, hoist the car and grab the wheel/tire top/bottom and check for worn bearing type movement.

Its hard to 'feel' any roughness by hand in these when the bearing is not loaded.

I think you can disable the ABS by pulling a fuse, not sure.. Just for diagnosis of course.
Click to expand...

I appreciate all the replies I've received so far. Thank You to all!!!

To start with:

I grabbed the wheel at top and bottom, then left and right, and wiggled as hard as I could. The only looseness I found was right front wheel in the left to right wiggle. I was doing this by myself, but near as I could tell the looseness was from the outer tie rod end. This wiggle movement was almost imperceptible. Maybe I can get my son or daughter this afternoon to help so I can be sure about the tie rod end. I then spun the wheels without feeling, or hearing, any roughness. When driving the car I hear no sounds like a rough wheel bearing.

At this point I have not unplugged any of the wheel sensors. It looks like I will be taking the car into town this afternoon since the wife didn't go to work today because of back pain. I will to to O'Reillys, or ?, and get the codes read. I also want to get a can of tuner cleaner. I will then take apart the sensor connection at the wheel and check and clean them. John suggested checking the connections at the ABS unit. Will do that, and clean with the tuner cleaner. Since WW suggested checking grounds (hadn't thought about that) I will go to the library and see if I can find a schematic denoting locations of the grounds.

I will also get new pads and rotors for the front. It looks like in the past the pads were replaced without turning the rotors as the inner face of the rotor, especially on the drivers side, is worn way down into the rotor face, leaving a substantial ridge on the outer diameter of the rotor. This makes me think the rotors are not surfaceable, and still be within specs.


WW, I have a digital multi-meter, but no scanner, so I will keep your suggestion about the IG switch and voltage in mind. But, I will be focusing on the brake end first, especially rebuilding the front brakes.

Again, thank you all for your help. I will update this evening on what I get done.

Don
 
Ground for the ABS unit is usually large and easy to manually track down. It is also a TSB for 2005 trucks to clean the ABS ground due to ABS codes.
 
Here's what I did today:

I went over the front brakes. The calipers were in good shape, piston boots showed no damage or problems, pistons retracted into the bore easily. The rotors were definitely in poor condition. The back side of each rotor was worn so deep that I didn't think they would clean up and still be within minimum specs so I replaced them. The pads were all worn flat, but the drivers inside pad was less than 1/8" thick while the outside was over 1/4" thick. That side of the rotor showed the excess wear by how deep the surface was worn. The passenger side pads were fairly equal in thickness. If the pads on the drivers side had been as equal they would have had probably 10K miles in them.

I took the ABS connectors at all four wheels apart. They were clean inside, showing no signs of problems. I checked the wires leading up to the sensors. The wires were all in corrugated wire loom and showed no signs of rubbing or damage. I went into town and got some electronics/tuner cleaner and sprayed down all the connectors before re-connecting them. After getting everything back together I replaced the ABS fuse I had pulled out last week. At this point the ABS light never came back on. The SES light is on so sometime in the next few days I'll meet my wife in town after she gets off work and get the codes read.

I'm not real sure just exactly what I did to correct the ABS light problem since I did more than one item at a time. But, I didn't want to put wheels back on the car after doing the front brakes to check for the ABS light, and then pull them back off to check the ABS sensor connectors.

Thank you all for giving me ideas what to be looking for and checking. When I get the codes read I'll post up what I find there.

Don
 
The ABS system is VERY picky about connections. My Impala would occasionally have the ABS light come on. All I had to do was unplug the connection under the drivers seat, clean the connections (they didn't look bad btw) and plug it back in and the light would stay off for a few months.
 
Update:

Been a very busy week for me. I finally got a chance to check the codes. The car hadn't been driven since I did the front brakes since my wife is on spring break at her job. As I was driving into town the SES light went out and didn't come back on. Of course, there were no codes stored in history either. So I'm in the watch and wait mode now.

Don
 
GROUNDS, GROUNDS, GROUNDS, this sounds like a loss of ground issue to the ABS. If the ABS module loses power, ground, or if the data bus loses coms with the ABS it will turn both lights on. GM also has quite a few issues with sensor gap problems. What happens is over time rust builds up underneath the sensors in the hub bearings, and this pushes the gap apart. The fix is to pull the sensor out and clean the rust off so the sensor can sit in all the way again.
 
When I was checking/cleaning the ABS connectors at the wheel hubs I also looked to see if there was any visible way to disassemble the sensors. Everything looked sealed to me. I also looked at the pictures on the Rockauto site and everything looks like its all pressed together. From appearances the whole hub has to be removed to even get at the sensors. Am I not seeing everything correctly? This ABS stuff is all new to me so I'm as green as can be.

I'm not discounting rust, but around here we seldom have snow. And when we do, salt and chemicals are never used, only sand. Other than dirt, I'm seeing no sign of rust anywhere.

When I have a chance I will haunt the local library to see what I can find for ground locations.

Don
 
sensors are integrated into the hub, nothing you can really do with them except plug and unplug the electrical connector.
 
That was what it looked like to me, but being real green with ABS I needed confirmation one way or another.

Thank you.

Don
 
I'll say again to stress the importance. Check/clean ALL electrical connections on the entire ABS system, especially grounds. ABS is very picky about it.
 
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