ABS Problem (maybe)?

1998 Silverado 1500 4x4: This one is a good one. When I am approaching a stop sign moving slowly, I can sometimes feel a little bump (like it will pop up and let down quickly) in the brake pedal, then a mild ERRRRRRRRRRRRR sound that is coming from the engine compartment (I assume it is the ABS unit). That has been happening occasionaly, then today was the topper. While leaving a stop sign, I accelerated to about 40 miles per hour and noticed the speedometer jerked back down to zero and back up again rapidly about three or four times. While the speedometer dial was doing this the transmission slipped like it was popping in and out of gear. While this is all happening the ABS light comes on and stays on. I can turn the truck off, restart it and its good for a while till it happens again. Anyone have any good ideas what the heck could be causing this? Front pads are new, rear shoes are at 50 percent. Can the ABS effect the speedometer and transmission? Hard one for me to swallow, I am old school and speedo cables either are broken or not.

When I am approaching a stop sign moving slowly, I can sometimes feel a little bump (like it will pop up and let down quickly) in the brake pedal, then a mild ERRRRRRRRRRRRR sound that is coming from the engine compartment (I assume it is the ABS unit).
You have a mis-match between ABS sensor outputs...the sensors are located on the wheel hubs. Do a search on the forum on ABS and you will find how to test them. As far as the other things going on...fix the sensor problem first and I bet the rest go away.

1998 Silverado 1500 4x4: This one is a good one. When I am approaching a stop sign moving slowly, I can sometimes feel a little bump (like it will pop up and let down quickly) in the brake pedal, then a mild ERRRRRRRRRRRRR sound that is coming from the engine compartment (I assume it is the ABS unit). That has been happening occasionaly, then today was the topper. While leaving a stop sign, I accelerated to about 40 miles per hour and noticed the speedometer jerked back down to zero and back up again rapidly about three or four times. While the speedometer dial was doing this the transmission slipped like it was popping in and out of gear. While this is all happening the ABS light comes on and stays on. I can turn the truck off, restart it and its good for a while till it happens again. Anyone have any good ideas what the heck could be causing this? Front pads are new, rear shoes are at 50 percent. Can the ABS effect the speedometer and transmission? Hard one for me to swallow, I am old school and speedo cables either are broken or not.


the transmission sensor monitors the rear wheels, the front left/right sensors monitor the front wheels....the transmission sensor goes to abs and speedometer...if this is bad/dirty/wiring defective,,,, abs and speedo/computer will get into slip/slide mode....your symptoms..

Front sensors are good, now I'm going to find a way to test the speed sensor. Thanks, and I'll post how this all finishes out.

How did you test the front sensors?

Front sensors are good, now I'm going to find a way to test the speed sensor. Thanks, and I'll post how this all finishes out.

THE FRONT SENSORS DO NOT GO TO THE SPEEDOMETER !!!!!!


The transmission speed sensor/wiring/connector has issues most likely...this is the signal that the speedo is using....as well as the ABS.........

THE FRONT SENSORS DO NOT GO TO THE SPEEDOMETER !!!!!!
Why are you yelling?

THE FRONT SENSORS DO NOT GO TO THE SPEEDOMETER !!!!!!


The transmission speed sensor/wiring/connector has issues most likely...this is the signal that the speedo is using....as well as the ABS.........

1st off this message was not directed to you......2nd I previously stated this fact and i felt it was somehow not clear....as he checked the front not the transmission speed sensor

I see...I'm still waiting to hear how he tested the front sensors.

I used a voltmeter and checked the resistance of the sensor. once I connected the leads, I spun the wheel to make sure the resistance changed. They both did. I also moved the wires around to see if the resistance changed. If it changed from moving the wires I would have suspected the wires. You know, after I disconnected both front sensors and checked them it stopped having the problem for about three days. Just started again so I am going to mess with the speed sensor. Is there a good way to test the speed sensor??

Thanks

You need to check the sensors the same way except set the volt/ohm meter to AC milliamps. 350ma is the minimum per side but the one with the largest drop is the bad one.

I used a voltmeter and checked the resistance of the sensor. once I connected the leads, I spun the wheel to make sure the resistance changed. They both did. I also moved the wires around to see if the resistance changed. If it changed from moving the wires I would have suspected the wires. You know, after I disconnected both front sensors and checked them it stopped having the problem for about three days. Just started again so I am going to mess with the speed sensor. Is there a good way to test the speed sensor??

Thanks


in addition to shorted ,open, connector damage etc......remember if the sensor pick up head is containinated with metal debris the sensor out put will drop....low a/c milli volts and this will cause problems such as yours..


removal and cleaning may be necessary.....if any of the 3 sensors have metal on them this abs/speedometer problem may be the smaller problem as this should not occur..

The simple solution to this is a scan with an abs function scanner which will allow someone to see the speed sensor inputs and compare which one drops out at low speed, causing a false activation of the abs. This happens so quickly a dvom will not pick it up, only a scope or the scanner will. A common cause of this was rust build up under the ft speed sensor mounting flange causing the sensor to back away from the tone ring, causing a weak signal at low speeds, GM had a recall for this in the " salt" states.

This happens so quickly a dvom will not pick it up, only a scope or the scanner will
Wrong...if you jack up the front end of the truck and spin the tire with a VOM attached you will get a reading...I have done it and the info on how to do it came from a GM tech bulletin.

Well, I tried to clean the connector on the speed sensor now the truck is undrivable. It's stuck in first gear and speedo goes berserk. I used TV channel cleaner to clean the connector and sensor contacts up (didn't look dirty or corroded). It didn't like that at all. So it looks like it is either the sensor, a bad connector, or possibly (and I hope not) some kind of short in the wirring from the sensor to where ever the heck it goes. I think I'm gonna say uncle and bring it to someone with a reader and pull a code out of the stupid thing. I should go buy something with a speedometer cable and points :)

Well, I tried to clean the connector on the speed sensor now the truck is undrivable. It's stuck in first gear and speedo goes berserk. I used TV channel cleaner to clean the connector and sensor contacts up (didn't look dirty or corroded). It didn't like that at all. So it looks like it is either the sensor, a bad connector, or possibly (and I hope not) some kind of short in the wirring from the sensor to where ever the heck it goes. I think I'm gonna say uncle and bring it to someone with a reader and pull a code out of the stupid thing. I should go buy something with a speedometer cable and points :)

if you still had an intermitent problem, use of a scope is preferred....this i have used in repair of transportation vehicles with wheel slip errors....usually a connector/wire shorted is the problem....

but since it is now totally scewed up and you can not find the problem i would think it best to have a competent repair person troubleshoot this problem ...with the proper test equiptment and training this is a simple repair......

This happens so quickly a dvom will not pick it up, only a scope or the scanner will
Wrong...if you jack up the front end of the truck and spin the tire with a VOM attached you will get a reading...I have done it and the info on how to do it came from a GM tech bulletin.
Wrong!? I' ve spent many hours doing abs repairs particularly on these trucks, driving with an abs function scanner picks up the drop out below 6 mph every time, the dvom test is spotty at best and may not be quick enough to pick up the described condition, yes it will work on a dead or high resistance sensor.

Wrong!? I' ve spent many hours doing abs repairs particularly on these trucks, driving with an abs function scanner picks up the drop out below 6 mph every time, the dvom test is spotty at best and may not be quick enough to pick up the described condition, yes it will work on a dead or high resistance sensor.
You either get milliamp AC voltage or you don't....what's so hard to understand? The way you do it is the absolutely the best...but if you want to test it yourself the VOM (volt ohm meter) works on the voltage from the sensor itself. Anything under 350 is bad or if there is a big difference between the two sensors the lower one has a problem.

Agreed, I am just more comfortble and have had more consistant results with the scanner, I understand that most dyers do not have access to this equipment. Normally the sensor drops out at 4 mph anyway and that short time frame from say 6 down to 4 or below can be tough to see on the dvom. BTW after 45 years, this is not hard to " understand"!

You either get milliamp AC voltage or you don't....what's so hard to understand? The way you do it is the absolutely the best...but if you want to test it yourself the VOM (volt ohm meter) works on the voltage from the sensor itself. Anything under 350 is bad or if there is a big difference between the two sensors the lower one has a problem.


There is no way a volt/ohm meter can read out what a speed sensor is actually reading or catch drop outs or improper speed sensor readings.
It only tells you if the sensor is generating a signal.

You need a good abs capable scanner to read out all speed sensors.
The newer and better scanners graft out sensor readings where you can see glitches and drop outs
The sensors have to match at all times with no drop outs or glitches..
Also a lab scope may be needed to catch the hard to find glitches and dropouts from tempt change or shorts from wet driving conditions.

Just going by a volt/ohm meter reading will lead to throwing parts at it and a lot of extra expense and head aches.
MT

On the TV cleaner, was it the type with lubricant if it was it can act as an insulator. Try using alcohol. You need to use a spray that has no lube in it.

I have an OTC 4000E scan tool with an 02 duece and an ABS cartridge I purchased at the same time. It is getting outdated. Has anybody used the Actron ABS scanner around $200.00 on ebay for new unit. Are they worthwhile for home use.
If I upgrade my 2000 silverado due to fuel costs I wanted something for a newer vehicle.

Just going by a volt/ohm meter reading will lead to throwing parts at it and a lot of extra expense and head aches.
MT
Then why is there a GM tech bulletin out that says to do exactly what I said? I had problems with my ABS and used a volt-ohm meter and the left side was not generating enough voltage...I replaced the left sensor and guess what...I must have thrown the right part at it because the problem went away...
I'm not saying it's the best way to check...only a place to start...and the info came from GM and it worked in my case. If, I couldn't tell if I had a bad sensor then I would have taken it to a dealer and paid a lot of money just to plug a device in for 30 seconds. I know they have to pay for the scanner but I fixed it myself and guess what...the info about the tech bulletin...came from this forum that you guys run and it, the forum, has saved me thousands of dollars over the years of which I am very thankful...:bigthumb:

GM is not doing the fix right.They should look into replacing the wheel bearing which will fix on the spot instead of cleaning the speed sensor.My father's 2002 GMC 4x4 dually had this problem and went away after replacing the left front wheel bearing.

GM is not doing the fix right.They should look into replacing the wheel bearing which will fix on the spot instead of cleaning the speed sensor.My father's 2002 GMC 4x4 dually had this problem and went away after replacing the left front wheel bearing.

Do you mean wheel bearing or wheel hub? The hub is complete with a new sensor and should fix any sensor or rust build-up around the sensor problem.

Replace the wheel bearing and GM does not cover the wheel bearing under the recall.Most new wheel bearings come with the ABS wheel speed sensor installed.Sometimes the wheel speed sensor does not come out intact of the old bearing,snaps right off and you're off to the dealer for a new one.

Just going by a volt/ohm meter reading will lead to throwing parts at it and a lot of extra expense and head aches.
MT
Then why is there a GM tech bulletin out that says to do exactly what I said? I had problems with my ABS and used a volt-ohm meter and the left side was not generating enough voltage...I replaced the left sensor and guess what...I must have thrown the right part at it because the problem went away...
I'm not saying it's the best way to check...only a place to start...and the info came from GM and it worked in my case. If, I couldn't tell if I had a bad sensor then I would have taken it to a dealer and paid a lot of money just to plug a device in for 30 seconds. I know they have to pay for the scanner but I fixed it myself and guess what...the info about the tech bulletin...came from this forum that you guys run and it, the forum, has saved me thousands of dollars over the years of which I am very thankful...:bigthumb:


this bulletin with ABS problems at low speeds is very different than this guys problem.....his problem is intermittent [or was] speedometer and ABS issues which now has increased to transmission shifting problems....from where i am sitting i believe his transmission has problems , which has affected the speed sensor mounted in the transmission....


only a skilled tech with the proper equiptment will be able to accurately diagnose this one...

Okay, It is the speed sensor (I know some of you guys are thinking DUUUUUUU). I had someone put it on a reader and it gave him the code indicating a speed sensor. This doesn't necessarily mean it is the sensor so I tried one off of an identical truck and it worked.
Now, for my next problem. I am an Italian and I'd just as soon have a telephone pole shoved half way up my $#&$# before I pay $150.00 for that little speed sensor. Anyone know where to get them cheaper? Should I go OEM and get bonned in the *#(*$#? It kills me to get raped like that. Any help would be appreciated.

Thanks

Okay, It is the speed sensor (I know some of you guys are thinking DUUUUUUU). I had someone put it on a reader and it gave him the code indicating a speed sensor. This doesn't necessarily mean it is the sensor so I tried one off of an identical truck and it worked.
Now, for my next problem. I am an Italian and I'd just as soon have a telephone pole shoved half way up my $#&$# before I pay $150.00 for that little speed sensor. Anyone know where to get them cheaper? Should I go OEM and get bonned in the *#(*$#? It kills me to get raped like that. Any help would be appreciated.

Thanks


get list of vehicles that use this part and go to scrap yard and get a few sensors....make a list of other parts you need and have at it...

The used part from the yard may be the old, bad, design. It's life may be used up. It may be defective. It may be the original design was flawed. Any one of those things would cause you the same problem again.
With any luck the new part you buy would have the original defect corrected.
At my job our customer is quick to inform us when our parts have failed. Whenever possible we redesign the part to improve it.
Can you at least have the junkyard test your parts to see if they are good?
Good luck.

Or it may not come out intact,break off in the wheel bearing.I tried getting one out of an old wheelbearing that was junk and it snapped off.You cannot get the speed sensor aftermarket and is a dealer part only.

They have a couple of used ones on ebay do a search.

The used part from the yard may be the old, bad, design. It's life may be used up. It may be defective. It may be the original design was flawed. Any one of those things would cause you the same problem again.
With any luck the new part you buy would have the original defect corrected.
At my job our customer is quick to inform us when our parts have failed. Whenever possible we redesign the part to improve it.
Can you at least have the junkyard test your parts to see if they are good?
Good luck.


my sensors are 8+years old closing in on 120,000mi and they work fine...for 150.oo you can get a bushel of sensors at scrap yard...and if you insist they will give a 30day warrantee just as good as GM new....

if this were a new vehicle i say no, but lets be realistic, how many more years is this guy gonna keep this vehicle....

My last truck was a 1986 Ford Ranger and my wife had to talk me into buying this 1998 in 2005, like I said "cheap Italian". I'd rather have another half a telephone shoved up my %&%) before I'd give anyone over 30,000.00 for any truck. The truck is in very nice condition. Prices on everything are getting stupid and as long as people pay it it isn't gonna get any better. Napa Auto Parts has a sensor for 100.00, but if it is anything like their pulse boards for the windshield wiper motor forget it. That lasted about two months before it started getting a mind of its own. Anyway I called the Chevy dealer and they needed to know the last 8 digits of the vin number so the sensor would match my transmission. So then how can Napa Auto Parts just hand me one without needing to know the same info (the part would probably suck). Anyway I found a way to get an OEM sensor for 100 even (only about a quarter of a telephone poles worth). Looks like I will have to bend over and pay the hundred and the case will be closed. Bastids.

The dealer I went to several years ago said GM doesn't sell the sensors...you have to buy the hub. There are places like NAPA that sell them but I bought a sensor that was used and it works just fine.

This is the speed sensor that mounts into the transfer case, not a wheel sensor. I just picked up the new one and walked out the door like a penguin due to a sore anus after shelling out the money for the tiny sensor. Case closed, another case of having the customer by the nads. Down with hosing people who are capable of making their own repairs. Thank you all for the help and suggestions.

This is the speed sensor that mounts into the transfer case, not a wheel sensor. I just picked up the new one and walked out the door like a penguin due to a sore anus after shelling out the money for the tiny sensor. Case closed, another case of having the customer by the nads. Down with hosing people who are capable of making their own repairs. Thank you all for the help and suggestions.


it's people like you that allow these part supplyers to get 100.00 for a 10.00 part....the scrap yard has saved me and many others from a sore ass...where i worked i was considered cheap but i learned from the master cheapo's and they leave me in the dust...pick up stuff at the dump and sell on EBAY.....that's how they operate..

You must not be from Northern California my friend. Wrecking yards in my neck of the woods charge 50% of what the part costs new and they have little books to look it up in. I think that would change your tune if you were rolling the dice on a $50.00 junk yard part to save half of the price of new. And lots of these guys won't take those types of parts back. So put that in your wisemans pipe and smoke it biotch :grinyes:

You must be going to specialty yards I know in the Atlanta area Volvo and Toyota yards are like this but if you check around other yards are cheaper.

You must not be from Northern California my friend. Wrecking yards in my neck of the woods charge 50% of what the part costs new and they have little books to look it up in. I think that would change your tune if you were rolling the dice on a $50.00 junk yard part to save half of the price of new. And lots of these guys won't take those types of parts back. So put that in your wisemans pipe and smoke it biotch :grinyes:


earthquakes, wild fires, and now this Junkyard rip off's.....I been to CA. and things are very different from the right coast where I'm from.....


There is a scrap yard in my area that has specials....people will get a large hood fill it with parts and they charge 75.oo or so if you can drag it off the property.....



with all that illegal cheap labor in CA. I bet they will break down each vehicle to the basic parts and sell even the used nuts and bolts..on EBAY...

That is correct. Broke down and catagorized awaiting some poor unsuspecting bastard that may need the part. Im not looking in specialty yards rhanwor. Just random wrecking yards. Pick-N-Pulls might be cheaper but are kind of far away. And your right about the labor, I see all Mexican people working in the wrecking yards, Pick-N-Pull is the only yard left that lets the buyer pull anything off of a car. The rest of em have the part pulled for you or its already on a shelf somewhere. California is a beautiful state but seems to be slowly dividing into the haves and have nots (if you know what I mean).