Technical Abs pump don't assume the worst.

[RobL]

Knaus Sunliner motorhome x230 2001 2.8jtd.
Abs light illuminated intermittently at first mostly in wet weather and eventually continuously.
I don't have the equipment to do diagnostics and garages claim that their equipment won't connect to the vehicle (to old).
I replaced all the sensors, problem still persisted. I assumed the Abs module was faulty so removed the pump and had it tested. The pump passed the tests. I then assumed the problem was electrical and did various multimeter checks which didn't show up any problems. The harness plug appeared fine no corrosion or anything obvious. I cleaned it anyway with plenty of contact cleaner and good scrub with a brush. Plugged it into the Abs and light went out and has stayed out.
I could have averted a lot of time and effort by simply cleaning the plug. Hopefully this will help someone in the future with the same problem.

 

[bugsymike]

Knaus Sunliner motorhome x230 2001 2.8jtd.
Abs light illuminated intermittently at first mostly in wet weather and eventually continuously.
I don't have the equipment to do diagnostics and garages claim that their equipment won't connect to the vehicle (to old).
I replaced all the sensors, problem still persisted. I assumed the Abs module was faulty so removed the pump and had it tested. The pump passed the tests. I then assumed the problem was electrical and did various multimeter checks which didn't show up any problems. The harness plug appeared fine no corrosion or anything obvious. I cleaned it anyway with plenty of contact cleaner and good scrub with a brush. Plugged it into the Abs and light went out and has stayed out.
I could have averted a lot of time and effort by simply cleaning the plug. Hopefully this will help someone in the future with the same problem.

There are several different types of ABS systems with different methods to test, I have done a few over the years but none were the actual ABS pump or Module on it. The older ones were Vane type which a visual inspection could show up damage, nowadays the active type use a magnetic rotor often inside the wheel bearing and simply a brush with a magnetised screwdriver is enough to cause failure.
A voltage drop from a poor connection such as you found is another.
On a 4x4 Skoda I was getting around 8 volts at the n/s/f and 12volts on o/s/f it was known that the loom inside the wheel arch was the common area of trouble, unfortunately for me it was a fault further inside the car where for some strange reason the loom doubles back inside and then continues to the ABS unit under the bonnet, but I located it in the end.
Sometimes parts suppliers have only one type of sensor listed for a certain model but by checking the similar model badged for a different manufacturer suddenly listed a choice of two so correct one was obtained, a case of the computer says no, but experience says check!