ABS and BRAKE lights come on above ~ 35mph

[BK]

So I have a 99 4x4 2500 CTD RAM.
It sat around for a few weeks in the late winter while I pulled the dash out and rebuilt the HVAC box.
I had disconnected all the wire harnesses under the dash so I could swing / suspend the dash out of the way.
For the few weeks it sat around, the batteries were disconnected.

Got it all back together, went for a drive and the ABS and BRAKE lights came on, speedo works fine.
Finally got around to replacing the RWAL tone sensor.
But exactly the same issue.

But for looking to make sure I didn't break any associated wires, any other ideas based on the symptoms?
Seedo good.
ABS and BRAKE lights will come on at about 35mph or more... if I just cruise slowly around the neighborhood the havent come on.
Brakes feel great , fluid level is fine. No leaks that I could find.
This was not happening before I rebuilt that HVAC box.

TIA,
Bob

 

[DavidC]

There is a plug on the back of the trailer plug. Disconnect it, clean and go for a ride. I had the same thing happen years ago. Cleaned both sides as best I could and reassembled with dielectric grease. The only way I could get it to reset was to shutoff the truck and restart then about 40mph it would all happen again. Nothing was done to the truck, the problem just came from nowhere. You may take a look at the trailer plug itself also.

 

[BK]

David, thanks for the reply.. do you mean the trailer 7way thats on the back of the truck?

 

[DavidC]

David, thanks for the reply.. do you mean the trailer 7way thats on the back of the truck?

Yes, unplug the harness for it on the back side of the 7 way. Hopefully it's there and not in the harness.

 

[BK]

Soo strange.. did you redo a ground to the chassis that is near by, or just inplug the truck harness from the 7way and clean and reassembly (as you stated, but just want to be sure I'm not missing something in translation ) tnx!
Bob

 

[DavidC]

I did nothing, nor did I see anything. Thought it might be the controller. Had me baffled then I stumbled upon the fix. There are also 3 or 4 plugs in the drivers wheel well near the cab that go to the back but I did not have to mess with those. Yes it was strange the way it happened but the rear sensor just popped up one time also with no reason.

 

[DavidC]

I unplugged the harness on the back of the 7 way then went for a ride. No lights so I knew I pin pointed at least the area.

 

[BK]

I unplugged the harness on the back of the 7 way then went for a ride. No lights so I knew I pin pointed at least the area.

Thanks, appreciate clarifying for me. I'll take a gander, been ages since I've even touched that harness/area. Just trying to think how it might influence the WSS / RWAL / CAB stuff.

 

[DavidC]

I don't know how it back fed in the system, there is 12vdc at the plug along with the brake system for lights. After it fixed the problem I stopped investigating and was glad it wasn't the ABS controller.

 

[BK]

I hear ya! that's been my scare now, after the rear axle WSSensor didnt do it.
Or loss of calibration , is the fear, reading the manual, if you replace the controller, it needs to be programmed for the axle ratio and tire size.
So far , in searching the web, not finding anyone with the same issue you and I experience... speedo great, up at some speed the ABS & brake lights light.
But the WSS is the MOST common thing to fail, so figure wth.
I've been looking at the wiring diagrams , and looking for the inputs and what ties to what...but for the 4x4 selector input, haven't found any surprises.
Even if I had broken a wire when disconnecting all the harnesses under the dash, I wouldn't think that this behavior would come from a broken wire.. this is ok at low speeds and not happy at some higher speed, figure broken wire would be all lights all the time, more so during start up self test.

 

[DavidC]

If it was the rear sensor the speedo would not work, that's why I looked elsewhere.

 

[BK]

I thought so too and agree with you. But read (but never spoke with) some that didn't complain of the speedo, just the lights coming on.. for 20bux, and 10mins of work figure would just eliminate it. I'll have to dig into the 7way tomorrow.. still cant fathom, but hard to argue with results.
I was thinking grounds, but the WSS is a twisted pair up to the CAB.

 

[DavidC]

I'm betting on a back feed. Where exactly is the question.

 

[Ozymandias]

Diagnostic with proper workshop computer is what you need, not the parts gun.
DRB III is your friend.
During a ride connected to the ABS Modul you'll see what's going wrong.

 

[BK]

Diagnostic with proper workshop computer is what you need, not the parts gun.
DRB III is your friend.
During a ride connected to the ABS Modul you'll see what's going wrong.

Very much appreciate the idealism...
Got one I can borrow?.. would love to...
Or do you know of a cheap / aftermarket substitute ?

So here's the rest of the back story.....
Well the scanners I have, wont give me ABS codes. Spoke with another buddy with 2000year 2500, same issue when he had ABS issues, couldn't read the codes.
He went to his buddy's shop , snapon readers, nothing.
Spoke with my local shop, same issues, they cant read the ABS system codes with all the scanners they had, and were the 2nd ones to tell me, need a dealer tool.
Hence why I've had this issue for about 3 months... gave up trying to find someone with the Chrysler OEM reader.
So have to get down to schematic Trouble shooting, but started with the most likely, most common failure... that WSS. 20bux and 10mins...
Seems that $3K for that Pentastar box (that no-one I know has one), is a lot more bux then a $20 WSS and a $10 brake switch from the parts gun, even if I eventually go with a 100 CAB.
Don;t get me started on the dealers...
My dealer can't tell a bad window switch from a bad power windo motor... they have all the tools and still charge to use their parts gun.
In doing more research after I bought the $20 WSS, one guy I heard from, dealer said it was the CAB, turned out to be the brake switch.
So not looking to ring up dealer fees. and so far the total sum of all the parts that it could be are less than yet another cheap scanner.
I hate changing parts, dont get me wrong, but buying a $3K tool VS $130 in parts..... vs the "dealer go around".................................

 

[DavidC]

No parts needed for T/S. Just time.

 

[Ozymandias]

AUTOENGINUITY will do the Job if you don't have access to a DRB III.
But yes, it cost you around 500$, but can be an investment into the future.
You can Diagnose all Chrysler vehicles with it.

 

[BK]

Thats a ton better than $3K , but right now, the total cost of all the parts are a 1/3 of that, and with still laid off due to covid19, waiting for the brake switch to arrive.
With 3 Jeeps in the family, worth the investment, when I'm back to work.

 

[Ozymandias]

Thats a ton better than $3K , but right now, the total cost of all the parts are a 1/3 of that, and with still laid off due to covid19, waiting for the brake switch to arrive.
With 3 Jeeps in the family, worth the investment, when I'm back to work.

Sounds good, with so many vehicles it is worth it anytime.
ABS is a pain to work on without diagnostic because there are so many things that can make a fault.

 

[BK]

Atleast with my Jeeps, when I lost wheel sensors on them, I could read those codes on them with the $200 programmer I bought for them.... my Ram and my friends Ram havent been as friendly.