2nd Gen Non-Engine/Transmission Abs/red Brake Light

[JWaters]

Well, lets see



I was so mad at this truck and this ABS problem that I went to trade it and about ***** when I seen the prices of the new cummins, I am already a hater of all the new electronics so I quickly said no way!!!



I posted about this ABS problem and I got some really good ideas but no one hit it right. I found the problem today and now the truck is fixed!!! I said it is FIXED!!!!



I spent 11 hours going thru the brake system from front to rear and I have checked all vaccum lines, wires,sensors,valves... ect... . well it ended up being the "Vaccum sensor" beside the fuse box under the hood on the drivers side. I did not have a qlue to what it was or did. I just knew my ABS light stayed on. I have replaced that and Now see is like new again!!!!



I love my truck and will keep it forever!!!!!



thanks

 

[MHalloran]

JW, you say "vacuum sensor". Is this the round "diaphragm" looking thing that is mounted kind of underneath a square-ish bracket that is bolted to the top of the wheel well- driver side? It also has the vac. line that connects to it on the top center of it? How did you know to replace this or was it just a LAST RESORT type of thing? My ABS/brake lites have been lit constantly for the last 4 days-- drivin' me nuts too! I also love my truck & want to keep it. Help me out brother! Mike H.

 

[JWaters]

very simple to test it since I know what it is now, Just unplug the wires going into the rear of it, if your light goes off... that is your problem. I pulled my hair out trying to find this. I thought it had to do with cruise control but really it tells the ABS computer that the truck is running. This is the only way the ABS computer finds out the truck is running. If it doesnt since a signal it will not go to self check and it will disable abs. I have a good rear sensor if you need it, that was a 70. 00 mistake on my part, the one sensor that everyone said was bad on the rear houseing my 96 has a different one than normal so I had to take back the 40. 00 one and get the 70. 00 on and it was still not fixed. But now It is!!!! Everyone who has a ABS light come as soon as key is turned on and it does not self check you better check the Vaccum sensor(diesel only)!! And yes that is the part!!! you are talking about!

 

[JWaters]

vaccum sensor

here is what it looks like and where it is.

 

[MHalloran]

JW, when you unplugged the wires from the vac sensor you said the ABS/brake lites went off. Was this while the truck was running? I tried this (while running) & the lites stayed lit :{ . Plugged it back in while running, then unplugged it, shut her down then re-started a while later & lites lit up even with sensor unplugged. Suggestions?

 

[JWaters]

buy unplugging it you found that it is not the sensor on your truck, so wee need to look else where.



Here is what to check:



Brake lights



Brake light fuse



ABS fuse



Unplug the small switch on the first block next to master cylinder, if light stays on continue to another test.



Unplug the dump valves under master cylinder



Do all of this with engine running.



Let me know if you run across it.



rear sensor on top of 3rd member, I have a extra one here that is good, I wasted that 70 bucks!



If non of that fixes it the you will have to pull the module and check the resistant from the rear sensor to the plug at the aABS module.

 

[MHalloran]

JW, what is "small switch on the first block"? & also what do you mean by "dump valves" ? Is this mechanic lingo? Sorry, I'm a turbine mechanic not an "auto" mechanic. :-laf . Lemme know, thanx.

 

[JWaters]

the secound picture shows a switch pointing towards 2:00 oclock right beside the master cylinder, that is the one I was talking about. The dump valves is under the master cylinder and you cannot see them in my picture. They have brakes lines and a 4 wire plug going to them.

 

[Kirwin]

Brake booster

MHalloran, do you have good brakes? What happens if you step on the brake pedal 3 times in succession with the truck idling? Put a vacuum gage on and see what vacuum you are actually running. I got into this thread late in the game but I would look closely for a vacuum leak on the brake booster or the lines going to/from it. Low vacuum will give first an ABS light then turn on both if its sensed long enough. The switch that JWaters replaced is the vacuum switch that inputs to the ABS control module. Do you have 4 wheel ABS or just 2 wheel ABS? Ken Irwin

 

[JWaters]

Here is a simple test to find out if you have a vaccum leak, I just fixed another truck that just left my shop today because of this'



Crank your truck with the ac off, let it run for 2 minutes, look for a small vaccum cap to the left of the master cylinder about 2 inches above it and it should be right at the rubber seal. It will have 2 small lines going to it. Shut the truck off and wait about 15 secounds, pull this cap off. If you here and feel no vaccum you have a leak somewhere. If it still has vaccum on it you have no leak.



SImple test, you can also pull the check valve out of the booster to see if it has vaccum, it should hold it for a while.



Let me know what you find!

 

[MHalloran]

JW, I let engine run, pulled wire off 1st block-lites stayed on,put back on,then un-plugged wires on dump valves-lites still stayed on :{ ,plugged that back in, continued to let her run, then shut down. Waited a few minutes then pulled cap off that vac. line- heard & felt good hissin' sound so I guess my vac lines are OK-no leaks. Also (Kirwin) my brake pedal stays firm at 3 pumps- brakes feel good. (rear wheel only ABS by the way, right JW?) I have rear brake lights that work fine & my cruise control works too. Looks like we may be headin' towards the sensor on the diff? I'll try takin' that apart again this weekend. Any more ideas? (Also FYI, I've never serviced the rear wheel cylinders. Do you think this may have any effect? Rear brake shoes have been good & are slow wearing)

 

[Kirwin]

Maybe the rear sensor

You can tell if you have 4 wheel anti-lock brakes by looking to see if there are wires running along side the front brake hoses to the front wheel sensors on the hubs. If you do you have 4 wheel anti-lock, if you don't, 2 wheel anti-lock. If you don't have any hydraulic leaks I wouldn't mess with the rear wheel cylinders. You can check them to see that they aren't leaking but I wouldn't replace them unless they are leaking. Is the master cylinder full? Have you had to add any brake fluid lately? I'm not trying to insult you, but just want to make sure we've covered all the bases before you spring for the rear differential sensor. Ken Irwin

 

[MHalloran]

Hey Guys, sorry I didn't get back to you right away, I was away. (Hey JW, the pics you took were great,by the way) Upon checking the wheel cylinders, I found that I had a leak in the driver side rear cyl. Resovoir level is still OK. Ya think a leak would cause ABS/brake lites to come on (& stay on still to this day)?

 

[WJB1]

had both lights come on and off while driving, they then stayed on and the auto door locks started clicking on and off. checked and found nothing. this was on a long trip while towing a 31' 5th wheel. about 100 miles later at 70 mph the problem found me. my rt. front wheel bearing let go completely. DODGE ONLY PART. no after market wheelbearing about $385. this fixed the problem.

2001 4x4 stock auto.