Both the yellow ABS and red Brake warning lights came on in my '99 E-350 with 4WABS as I was cruising down the highway on a long trip. I've gone through the manual as far as I can go, checking all the obvious, short of pulling codes.

The RABS instructions show you can pull codes by grounding a wire, but the closest B/O wire I found was on a plug in the engine compartment, passenger side. Grounding that wire did not result in the ABS warning light flashing. Further, my SuperChips 1715 did not produce any fault codes in diagnostic mode.

Does the 4WABS system require a specific code reader, or is there another wire somewhere that I need to ground to get fault codes?

Thanks.

 

Any help on this, folks? - GregA

 

When I had this happen, I changed the sensor on the top of the differential to correct the problem.

 

The rear diff sensor cannot cause both lights to come on.

I sent Greg the service docs this morning, hopefully he'll let us know how it turns out.

Steve

 

He will. I'll probably be able to hack away at it over the weekend. -GA

 

Hi Project - that is where you are incorrect because the sensor there can does cause both the lights to come on. I know, I know, all the books say that it can't. When I walked into the ford parts counter, without saying a thing but putting the part on the counter, the tech goes "Are both lights on?" I said yes and he said "A new one will fix it". It's only a $27 part if I remember correctly.

 

Resolved:

https://www.ford-trucks.com/forums/5...9-e-350-a.html

 

I was having a similar issue with my '99 E350, so I followed GregA's link to see what he might have figured out. You can see my post there to see the details, but the long and short of it was that I had pulled the codes and had multiple communication failure codes for all of the ABS sensors. Thus I was suspecting a module issue. Well, guess what. I don't know that anyone here will ever be able to explain it, but, I just went out and swapped the RABS sensor with one on another '99 E350 that I have here (that the ABS and brake lights were not illuminated on), just to eliminate that sensor as a possible source of the issue and low and behold, the ABS and brake lights are no longer illuminated on the van that had the issue and they ARE illuminated on the van that didn't have an issue, i.e. moving the sensors DID move the problem. So, the problem WAS the RABS sensor. How and why that would cause the system to code out that all of the other sensors were not communicating, I have no idea. But, if you have both the brake and ABS lights on your dash illuminated, replace the rear ABS sensor BEFORE you try ANYTHING else as you will likely be chasing ghost codes if you don't. I hope this helps someone else down the line.

 

As a follow up, after a bit of driving, both lights came back on. And sometimes, shutting off and restarting the van will reset them such that they stay off for a while. Also, there have been times that only the ABS light will be on. So, I swapped the RABS sensors back and there has been no issue with the other van, and now both light are on all the time on the problematic van. I bought a new RABS sensor (Delphi from Rock Auto) and installed it, but both light are still on. I've found that when I hold pressure on the brake pedal while starting the van, the lights will not come on until I release the brake pedal pressure. Thoughts?

 

Hi,
have you found the problem, I ask because I face the same problem.
Thank you and all the best

 

Yes, but it was 8 years ago and I don’t recall what it was. I remember having to replace the OSS on the output shaft, but I don’t remember if that was the fix or if I had a bad ABS sensor as well.

sorry

 

Hi and thank you for your answer.