I have a 1999 dodge ram 1500 2x4 sport. Have owned it since new. Having a weird issue with my brakes that just started about 3 weeks ago. Couple things happening (they don't happen at same time). Will be braking with normal pedal pressure, truck is starting to slow down normally--then feels like i loose brake pressure (like i am slipping on ice). If i try and apply the brakes harder, the pedal is hard. It will come to a stop but takes longer. Other thing that it will do, when i do come to a full stop--have pressure on the pedal, i feel a "click" in the brake pedal (is sometimes loud enough you can hear the clicks). The pedal will drop slightly after the click. It will click anywhere from 6-9 times before it stops with the pedal dropping each time. If i remove the abs fuse, the problem goes away. Would have no issues driving with the fuse removed but i loose my speedo (that is a bad thing for me). Not getting any abs codes or lights coming on. I did try and replace the rear diff speed sensor, did not correct issue. Is just rear abs system in this truck.

 

Are you sure its only RWAL?

For whatever reason, your PCM thinks the rear wheels are locking, so it is dumping pressure to the rear...... You should still have full pressure to the front...

Unfortunately, the PCM gets its clue about vehicle speed from that rear sensor as well....

 

Yes I am sure it is just rear abs. No front wheel speed sensors.

 

I have heard of a false ABS signal, but seems to be related to the rear speed sensor (is why I changed it). I do work in a service dept at a dealer, so I do have some basic equipment to check systems but nothing that will actually "watch" the ABS operation. Ill take it to a Dodge dealer, but would like some sort of direction what it might be before I take it there. My guys think it may be the hyd control unit but really not sure. Had one of my senior techs take it on a test drive, I got the "blank stare" when he got back. Dont understand why Im not getting any codes if it is something electrical.

 

Not every failure will generate a code. Some of the parts have more failure modes than you can shake a forest at..... and not a single one will set a code.

Given that the rear abs on these trucks is pretty useless in any event, I would be real tempted to just disable the system, and call it a day......

But, if you really want it to work..... Gonna need to be able to do some data logging, and see what the PCM thinks is going on, when the problem presents itself. Is it easily repeatable?

 

I can one or the other issue to happen very 2-3 brake applications. There isn't a lot of inputs to the PCM for the ABS system. The brake lines go from the master cyl through the control valves for the ABS and out to the brakes. Is it possible I have a internal leak in one of the control valves that is building up pressure on its own? I do have to drive and use my brakes at least a couple of times before I can get things to act up.

 

I don't think so..... The 'controller' is just a couple dump valves...... When you let off the pedal, pressure should go down to next to nothing. The PCM looks at wheel speed, (and possibly transmission output speed) to decide whether the brakes are locking or not.... I am not entirely sure just how that would work though, as the parts the two different sensor read, or mechanically connected.... they don't get a choice but be running at the same speed.

If your speedometer reads steady while the ABS is freaking out, it's likely not the sensor, problem has to be elsewhere.... Trouble is, I wouldn't even begin to know where to start looking.....

 

Any thoughts on the brake lines collapsing?

 

Now there's a thought. I have seen front lines collapse internally, and lock the front caliper..... Never seen a rear line do that, but, that by no means implies it can't happen.

 

If it was a issue with the brake lines, it should still act up with the abs disabled. The thing that I find really odd with what is going on is the "click" sound with the brake drop (when at a full stop). The click can be loud enough that someone in the passenger seat can hear it. I have up to 9 "clicks" with the pedal dropping slightly after each click. That just doesn't make sense under any abs applications. The "sliding" feel, that I can understand. Even if I am getting a false abs to/from the pcm, why it is acting this way?