I have had a problem with ABS in a Volkswagen T4 1993 pre-facelift since buying the car. The first winter, when braking hard, it still turned on from time to time (after restarting the engine, it went through a checking procedure). But, it eventually stopped working.
The solution came with the purchase of a VAG USB OBD1 Interface (about $130) and plugging into the bus computer. All the systems in it are just this ABS, nothing else seems to be able to be checked.
The indicated problem is a right wheel sensor error. Without this de facto diagnosis, it could take longer to find the cause. For example, a problem with the ABS control panel itself, a problem with the ABS lace, etc.
The repair is simple, but relatively time-consuming. At least for me it was, but I remind you that I have no experience in mechanics.
The old sensor, due to the fact that it was baked (apparently an affliction of the VAG group of this period and in this topic) immediately treated, was to be thrown away.
Useful tools were:
- chisel, tamp
- round file
- sensor (part number 701927807A)
- screwdriver, torx wrench
The repair is to lift the car, and remove the wheel. Then disconnect the sensor wires and try to remove it. Here, of course, it failed, and after several attempts, the sensor wire broke off from its attachment.
Then I tried to ream the sensor itself (from a small drill bit upwards), and after a while (not short at all) to get to the plastic sleeve that encased the sensor, after removing it already went a little more smoothly.
After removing the bushing, this was not the end of the work, it was still necessary to fight with the elements of the coil that remained in the hole.
Until I managed to clean the whole thing, so that the ABS system crown was visible.
The next step was to thoroughly clean the hole with a round file until the new ABS sensor entered it without resistance. Here, too, it took a while, but thinking how much time I spent on removal, I preferred to do it thoroughly.
Before inserting the sensor, I additionally greased the hole with copper paste so that the component could be replaced more easily in the future. It seems that if it doesn't help, it certainly won't hurt.
The end result, the ABS sensor works, the light does not illuminate, the brakes do not lock. After starting the engine, the light may still be on for a while, but it should go off by itself after driving a few meters.