From Tom Panzarella.
ABS system check V1
This Abs system was used by basically all the German manufacturers from the early 1980s to the early 90s.
I know a lot, from doing a lot wrong. Let’s go over what usually happens.
Start with the very easy option. Buy 2 new relays for the pump unit.
When I build a new Spec E30 I cut the harness out of the car and make my own. With that knowledge here’s my field troubleshooting guide.
I have no ABS at all, my car smokes the tires on the brakes.
Does your ABS light come on, and go out? If yes I’m sure your ABS Pump unit insides resemble the reactor in Chernobyl.
Send it out and get it rebuilt. Life will be good.
The ABS light goes on and off, but comes on when moving.
This is an issue with the speed sensor at the wheel, or in the harness to the sensor.
The method here starts with an OHM test at the ABS Module plug. This will eliminate the harness from being an issue.
(see below pin out for what to test, and the ohms you should see)
The Abs light comes on and stays on. With this you will need to go down the Pin out list.
If you end up matching what is listed, your issue probably lies in the pump unit or solenoid head. I have yet to pull one apart and not see a disaster of rusty crud in there.
This is measured at the connector on the ABS module (inside car)
When checking for voltage, have one end of your meter clamp to a good(not painted) ground. The other lead will do your probing
When Ohm testing your meter will be going between two pins listed below.
You will be ohm testing some wires between the module and the pump
Pin 1 (red/yellow) is Key on 12v
Pin 2 (brn/red) is to the left front valve control which goes to Pin 1 at the Pump (in engine bay)
Pin 3 is not used
Pin 5 is not used
Pin 4 red These are left front wheel speed input.
Pin 6 red
Pin 7 is not used
Pin 8 Green Left rear wheel speed sensor
Pin 9 Green
Pin 10 Brown/Yellow or Brown is ground
Pin 11 Yellow one side of the Front right wheel speed circuit
Pin 12 not used
Pin 13 not used
Pin 14 Black/Red is the “pump on signal” and ends up at Pin 9 on the pump. (If you where to check for the signal, easy thing to do is cut the wire and use a test in between your two ends)
Pin 15 Blue this is called the voltage monitor, it wants to see the alternator charging. You can literally wire this to anything that gets key on power too
Pin 16 not used
Pin 17 not used
Pin 18 Brown/white is the rear valve control circut, ends up at Pin 6 on the pump
Pin 19 not used
Pin 20 Brown- Ground
Pin 21 Yellow the other side of the front right wheel speed circuit
Pin 22 not used
Pin 23 not used
Pin 24 White Right Rear wheel speed sensor
Pin 25 Green/Red Brakes applied! this needs to see 12v when the brakes are applied
Pin 26 White Right rear wheel speed sensor
Pin 27 Black/white is Valve relay control goes to Pin 2 on the pump
Pin 28 Black relay control for the pump. Lands at Pin 11 on the pump
Pin 29 Green/Red abs indicator. Also goes to Pin 7 on the pump. This wire also goes to the indicator bulb. This wire is the 12v side of the bulb.
Pin 30/31 not used
Pin 32 is Yellow/Violet and goes to Pump Pin 4
Pin 33 not used
Pin 34 Brown (Ground)
Pin 35 Brown/Black to pump Pin 3