2nd Gen Non-Engine/Transmission abs & brake lights stay on.

[SSolderitch]

Started after making a 15 min stop on my way home from work on fri. When I started the truck, poped the e brake, noticed the lights stayed on. I checked the fluid, scotch-bright the pedel and the switch so to make a good ground. Made sure the pedal swings all the way up to contact the switch. I checked for codes - I have 1693, 1694 & 0500, which I always have... . light went out. Next trip came back on wile in route, twice. Now it stays on all the time. What should I check/replace? Should I clear the codes?

 

[rotohead]

On my 98. 5 with the same problem I replaced the ABS sensor on the top of the rear differental, I think around $40 from rockauto.com. I checked my bad sensor with a multi-meter and it should check to be 1800 ohms if good. Mine showed 'open' and I replaced it about two years ago and all is good. No lights or codes.

 

[Mishkaya]

Yep, almost always the rear wheel speed sensor. Do check your wires for chafing though, as well as the connectors for corrosion.

mishkaya

 

[SSolderitch]

thanks, I had the lights stay off for a 5 mile trip yesterday, but they are back on last night & again this morning. I will give the wires a quck look, everything will be white due to that brine spray... maybe swing by a car wash first. I should be able to check for1800 ohms with it still in the truck, right? before I buy another.

 

[San Felipe Bob]

I bet it's the rws

I vote for rear wheel sensor.

Thats what fixed mine... .



SFB

 

[rotohead]

I should be able to check for1800 ohms with it still in the truck, right? before I buy another.

Sure, unplug and use Multi-meter to determine. I haven't heard any other reason the sensor doesn't work properly other than internal failure. Good luck.

 

[dseabaugh]

my 97 does that any time I have a battery going bad. One reason I wish I never bought sam's batteries, but they keep replacing them. I guess they never planned on me keeping a truck this many years. Replace the batteries ( or charge them up) and no more idiot light issues. Go figure

 

[DieselDoghouse]

What SFB said about the rear sensor, also check your lines for any leakage since 'fluid displacement' will set the light off (happens when I change pads, also check the ground for the abs unit on the left fender. When I redid some wiring this set it off.

 

[KRineer]

If just the ABS light is on, I agree, it is the rear wheel speed sensor in the rear differential. I had this happen a couple of years ago, replaced it and it was gone. However, if both the ABS and the Brake lights remain on, that usually indicates a more serious problem. According to my 1999 factory service manual, it indicates a pressure differential.

 

[SSolderitch]

I changed the control box and I still have both lights. Planing on unpluging the switch wire on the purporting valve to see it the pressure differental is pushing the spool off center. I wonder if one of the abs relief valves are stuck open... .

 

[SSolderitch]

PS: I did clean the ground wire on the bracket stud.

 

[RHestand]

I'm bringing this thread up from the search forum, hopefully for more info:

I'm having the same problems as most of the above posts, with a couple of different quirks.

Mine started while driving cross country, empty, at 65MPH, when the cruise control kicked off, and the ABS/BRAKE warning light, came on simultaneously. Trying the pedal, the brakes seemed to be normal.

I took the first exit and checked all the things I could think of pertaining to brake problems. Fluid, good. No broken wires or obvious leaks anywhere.

I get back on the road,(The brakes work fine. ) set CC at 65MPH, and after about 5-10 minutes, my speed started fluctuating from 65 down to about 58MPH then back up to 65. It would do this cycle every 5-10 minutes. Then it would be fine for an hour or two. During all this up and down, the CC light stayed lit.

After arriving home the next day, and reading this among several other threads, I did a thorough under hood/under truck inspection. Still nothing obvious. I then pulled the speed sensor from the rearend, and checked it for 1800 ulms resistance. It showed 'open'.

Only one parts store here in this small town had one, so I went in and bought it. Before leaving I checked it for 1800 ulms, and it showed 'open'. The parts guy didn't have any answers, except to say "If I installed it, I couldn't return it. "

So where am I going wrong? Is the new one bad also? Can I pull up any codes on a 12V? What should be my next move? My truck is still on blocks and I need it.

TIA for any advice on this.

Ray

 

[Mishkaya]

It could well be that the new one is bad also, it does happen. If your speedometer shows fluctuations, it is likely it is the rear wheel speed sensor that is the culprit, although it could be the wiring harness going to it as well. Good luck!
On edit: it sometimes can happen that the brake switch at the pedal builds up enough corrosion to trigger the brake and ABS lights; in which case disassembling it and cleaning it can solve the problem, but your speedometer issue still makes me think it is the rear wheel speed sensor.

 

[Road Dog]

The ABS sensor is a Hall-effect transistor. You can't test it with an ohmmeter.
A regular code reader doesn't get codes from the ABS module. There's a separate data port behind the knee bolster under the steering column and a way to get the module to blink a fault code. With the brake and ABS light on it just means the ABS is deactivated. It's probably safe to drive.

 

[SSolderitch]

I unpluged the wire for at the porporting valve - both lights went out. I took out the switch and saw the spool was pushed down (groove not centered). I jacked up the truck and had no rear brakes when my wife pressed on the pedal. Changed out the master cylinder and everything is good again.

yes I had continutity across my old & new wheel sensor, I did clean the e-brake pedal ground also & the wire on the bracket.

 

[RHestand]

OK guys, mine is fixed. It was the wheel speed sensor.

Thanks for all the feedback, especially Road Dog for the "Can't be tested with an ohmmeter" info. My old one, and two new ones tested 'open'.

Plus, I had too many 'irons in the fire" when the brake warning lights came on.

Just before leaving (From WI to Wash. D. C. ) I had upgraded to new larger R. whl. cyls. , brake shoes, cut, bent, flaired, almost all of my rusty steel brake lines, new type brake fluid, then for good measure, a new dijital ohmmeter, I had never used before.

The feedback I just recieved is just one of the reasons I love TDR.

Ray