I'm on the road so I had to take truck to shop. Did my research here before I went in. ABS and Brake light on. No other issues; brake pedal was fine. Consensus found here was differential sensor was usual culprit. Shop got code and said sensor was bad. Replaced sensor and reset module. Driving home I get uneasy feeling about pedal but think I'm imagining things. Next day leave on next leg of trip. About 20 minutes out, lights come on. Pedal is also stiff at times, but not all the time. Lights go on and off during that day. At next stop do some more research here. Since I will be back at original shop in a few weeks, I just pull ABS fuse. Lights are back on, but pedal feels great, just like before I took truck in. I'm now back at shop, 2000 miles and six weeks later. I did put fuse back in. They can't find any code. Says the two problems are unrelated. I think I got a bad sensor and it is root cause of both problems. They want code to appear before they do anything. Anybody have any new ideas?

 

unfortunately most shops will do that, I ran into that with the bad sensor before, cheap parts will fail out of the box. not sure about the intermittent hard pedal, P.S pump or hydraboost

 

I did not state my question clearly. I know this sounds nuts, but it is fact. Put ABS fuse in and I get intermittent hard pedal. Take ABS fuse out and I have a normal pedal. What can I look for? I have done search and done hydroboost tests I found. Have no leaks, either vacuum or fluid. The only thing that makes a difference is the fuse in or out.

 

The ABS motor doesn't start running when you put the fuse in does it? Does the pedal vibrate or pulsate at all when it gets hard?

 

dodge24,

No and no.

 

I had 92 ram charger and that would do that. Disconnected the ABS and normal Pedel. Never hooked it back up and never had an issue. A really good service manager said that would be the cheapest fix. He said the senors and the control module will lose their mind and the senor is cheap if not senor then no ABS control unit. So I drove with out ABS till i sold it. best thing i ever did it stopped like champ after that.

 

Check the wire harness going to the rear speed sensor.
Mine was rubbing on the driver's side emergency brake cable near the axle.
It had rubbed clean through the outer harness sheath, and through the individual wire insulation causing them to ground out on the cable, kicking on the light and disabling the ABS (weird pedal feel)
Some electrical tape and a piece of fuel line slid over that area and ABS trouble free for two years.

 

Thanks for that tip. When I get home this weekend, I will do so.