ABS and Brake Light on - Not the usual suspects.

[MadMaximus]

2001 Dodge Ram 2500 4x4 with 5.9L 24v Cummins – ABS and Brake light on.

This is my "hail marry pass" before having to take this to a dealer. I have been trying to solve this for a month and I am at my wits end!

Current Situation:

· ABS and Brake Light are on.

· Brakes work correctly, firm but not grabby.

· ABS is disabled, no ABS. (Trust me, I tried it, no Bueno)

Here is what I have done, In Order:

1. Checked under the hood and in the cab fuses related to ABS, all good, continuity tested with multi-meter.

2. Replaced Passenger side Front Wheel Speed sensor. When doing that, found the caliper was frozen so replaced that, put new pads on front brakes and bled the system.

3. Replaced Rear Wheel Speed Sensor

4. Discovered Hydraulic booster was leaking replaced that and flushed power steering – hydro boost system.

5. Downloaded Service Manual and printed out all the schematics having to do with the ABS system and began testing resistance and voltages where applicable. As best I could tell all the wheel sensor OHMs where in spec, controller has correct power on the correct pins, no corrosion, no broken or frayed wires.

6. FINALLY bought a descent code reader and was able to pull several ABS codes, which indicated an issue with the CAB (Controller Anti-lock Brake) (Rear Isolation Solenoid malfunction.

7. Sent the CAB in to be repaired. They replaced a relay and a transistor, ran diagnostic and said it was good to go now. I got it back and reinstalled. No codes now, but still ABS and Brake Light on.

8. Replaced the Brake Pedal Switch (this is what turns on your brake lights and also sends this information to the CAB.

9. Tried forcing scanner to clear ABS codes, then restarted truck, still brake light and ABS light on, but scanner says nothing is wrong.

Other things to Note, Observations:

1. When turning the key from Off to Run, ABS and Brake Lights come on (with other lights) they go out (when I don’t have the parking brake set), and then 1.5 seconds later the come back on. That would seem to indicate to me that some sort of self-test has been run and is setting the light on.

2. If I disconnect the CAB (Antilock brake control module) the ABS light stays lit, BUT the Brake light goes out, which confirms to me that the brake light portion of this is not begin triggered by the parking brake switch, but by the CAB.

3. I even removed my Trailer brake controller on the off chance that it was somehow jacking with the system causing this, but that had no effect.

4. I have even stumped a Dodge mechanic, so I am really at a loss here.


The Question: After all of this what could be setting the ABS and Brake light on WITHOUT throwing any ABS codes?

And yes I have tried reading the codes and before the module was repaired, it was throwing codes.

 

[Timd32]

Read thru this and see if anything you have not checked, there is a VIN6 and VIN7 not sure if it makes any difference: wonder how you can verify the cluster is talking to the CAB? That's something I noticed not on your list.

Truck RAM 2500 Truck 4WD
L6-5.9L DSL Turbo VIN 7


ABS AND BRAKE WARNING INDICATORS
ABS Warning Indicator and Red Brake Warning Indicator (EBC 2 and EBC 325)

The system is equipped with an amber ABS and a red brake warning indicator to alert the driver of a malfunction it has detected. The CAB can control the operation of both the yellow ABS warning indicator and the red brake warning indicator via CCD BUS.

The CAB controls the ABS warning indicator by making it do one of three things:
^ light steady for 3.4 seconds during an initial test at the beginning of an ignition cycle to function as a bulb check.
^ light steady when a system malfunction exists.
^ light flashing if a vehicle speed signal parameter is faulty or missing.

The amber antilock brake system warning indicator is controlled by the vehicle's "smart" cluster. All Dodge Trucks are equipped with a smart instrument cluster that has direct control over the ABS warning indicator and red brake warning indicator. The cluster will periodically transmit a message over the CCD bus relating to diagnostics and current lamp status for the ABS and red brake indicator. The cluster will expect a periodic message back from the CAB indicating whether the indicator should be turned on or off. In the event that no signal is received from the CAB for a certain number of times, the cluster will turn on the ABS warning indicator. The indicator detects system related problems and takes diagnostic action.

The vehicle instrument cluster has a red BRAKE warning indicator to alert the driver to the following conditions:
^ parking brake applied
^ hydraulic failure in either front or rear channel
^ ABS system malfunction

The red brake warning indicator is controlled by the vehicle's "smart" cluster. There is a parallel path to chassis ground that will illuminate the red brake warning indicator:
^ through the parking brake switch contacts
^ through the brake warning indicator switch
^ through the CAB via CCD Bus

The CAB can control the operation of both the yellow ABS warning indicator and the red brake warning indicator
^ If the CAB is disconnected, the yellow indicator will be illuminated.
^ If the axle type or tire size are not programmed properly, the yellow indicator will blink.
^ If a system DTC is set, both the yellow and red indicators will be illuminated.

 

[Ozymandias]

I had this happen with my 04.5, finally figured out that the trailer connector was internally corroded and shorted.

 

[MadMaximus]

Thanks for the Feedback.

I did do the Key on while holding down trip reset to initiate cluster diagnostics, it completed diagnostics and reported no errors. Also if I start the truck with the C.A.B. disconnected the ABS light stays on as expected, but the red brake light goes off, which would seem to indicate to me that at some level the CAB is communicating with the cluster and is what is setting the Red Brake Light indicator.

As for the trailer connector, I replaced it a few years ago and have not had any issues with it. Ill spend some time testing the voltages and checking for shorts to rule it out, but I am skeptical but then I am skeptical of everything because I have been trying to figure this out for so long. Its almost an obsession.

Let me know if yall think of anything else.

 

[Timd32]

There is a parallel path to chassis ground that will illuminate the red brake warning indicator:
^ through the parking brake switch contacts
^ through the brake warning indicator switch
^ through the CAB via CCD Bus

If you can prove out those grounds would tell you what's turning on the Red Light at least.

I know I've read alot where folks just unplug the CAB and call it a day.

If you remember and fix it try to post back.

I know my 96 has both of them on, I'm not worried about it. Since the thing is so old the ABS was sketchy to start with just drive it within reason don't need ABS on mine.

It will most likely be sold with the lights on, good luck next owner. But will be fully disclosed at time of sale.

 

[MadMaximus]

So, I finally broke down and took it to the dealer. The confirmed the CAB (Controller Anti-lock Brake) is bad. He showed me when he put in their spare that all the lights went off. Unfortunately, he would not sell me that one.

SO I will be talking to the folks who "repaired" it, cause apparently they didn't. This is so frustrating.

 

[Timd32]

They are really tough to get back to life, lots are discarded in place.

At least you have a path forward.

 

[CharlesHoward]

My ABS AND Brake Lights have been coming on randomly for several years. Sometimes they don't go off on startup, sometimes they go on while driving. Code says "Left Front Sensor" is bad. So I bought a set of "fits your vehicle" (2005 5.9L 173K miles)" front Wheel Speed Sensors for about $40 online at Carparts.com and took them to my shop as this kind of installation is not for me nor is the needed "Brake Job".
So after a week the Shop calls and says the Dodge front Wheel Sensors are "built in", confirmed with Dodge, Dodge wants $1700 EACH, Shop says they found compatible "Moog" (?) Sensors for $800.
Yikes! I sure hope its just the Sensors and not the equally $$$$ ABS "CAB"....

 

[Ozymandias]

Buy a set of new unibearings for 300$ as they come with new sensors.

 

[GAmes]

Or unplug the ABS controller which costs nothing.

 

[MadMaximus]

1. I already replaced all the ABS sensors. (mentioned in my original post)
2. Unplugging the ABS in a 2001 Dodge Ram 2500 results in 2 things:

• a. The ABS light stays on.
• b. The speedometer, cruise control and odometer no longer work

THat said I did finally fix my problem.

I used a company called UPfix to repair my ABS module, as it was the ABS module itself that had gone bad. I also bought a salvage controller for $18 and had them fix that one as well, so now my truck is fixed and I have a good spare.

Moral of the story is, if all your sensors are replaced, tested good, and you have tested wiring and inspected it and everything checks out, then unfortunately the computer is the culprit.

And he drove off happily ever after.
The End.