ABS Troubleshooting


#1

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.

Option 1)

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.

Option 2)

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)

Option 3)

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


#2

Were the specified Ohm measurements coming in another installment?


#3

What specified Ohm measurements? All I see is tests for power and continuity. Maybe when he said “Ohm testing” he meant Continuity Testing.


#4

I was just referencing this comment, right above “Option 3)”, but maybe you’re right, and he meant continuity. Based on how he phrased it, doesn’t sound like it though. I’d be curious for Tom’s clarification.


#5

The wheel sensors are Hall Effect so they are little electromagnets. As such, they’d show a little resistance because of the small windings, but not much. I’m thinking that’s the only place where one could Ohms. That said, I’d just check for continuity there too. Sensors have no moving parts. If they have continuity the sensors should be good. The sensors wires lead a hard life and get beat up.


#6

The one thing here I don’t see mentioned, which I think is actually one of the main problems with my car, is the little light in the dash. If that is faulty, what’what are the steps to remedy that? I’d love to have a good remedy for that crappy little dash light that seems unreliable, at least to me.


#7