Constantly running ABS controller

[glennm01]

I discovered that the previous owner had the ABS controller unplugged, and maybe now I know why...when it's plugged in, it runs constantly, even with no key in the ignition. Pulling fuse FH4 (in the high current fuse box, labeled "ABS Valve") turns it off at least. Does anyone have any insight on this issue?

 

[gait]

interesting ..... what indicates its running? Do you have a circuit diagram for the vehicle?

 

[glennm01]

The motor inside the controller audibly fires up as soon as I connect it. This is with the truck shut down, and no key in the ignition. I have the service manual, which I assume contains a circuit diagram for this, but I haven't delved that deep into it yet. In reading about faulty ABS controller issues on other vehicles, it sounds like this may just be a typical symptom indicating the controller needs to be rebuilt (or replaced), perhaps due to corrosion mucking things up inside. I did remove the 4 torx screws to look inside for any obvious issues the other day, but everything looked quite clean.

 

[gait]

silly question .... have the brakes been bled? is there air in the system?

 

[glennm01]

Trust me -- there are no silly questions where me and vehicles are concerned. I haven't bled the brakes since buying the truck a couple of months ago, but the brakes feel pretty amazing, so I doubt they need it.

 

[kerry]

What year is your truck?

 

[gait]

I have no experience with ABS. Just where I'd look. The motor is probably driving a pump. Typically, the pump control electronics is broken and its producing constant pressure, or - either the pump has an airlock / isn't pumping anything, or the pressure continues to rise and the pump eventually stall.

 

[glennm01]

What year is your truck?

2004