E30 - ABS dash indicator light stays on

[windtrader]

I have a 1986 E30 325e, stock. It has been non-op for 5 years and I'm getting it rolling again. The ABS system and dash light worked fine for a long time but not long before being parked, the light started to occasionally gone on briefly then off again. Can not confirm if the actual ABS braking worked.

Currently, the ABS dash light goes on when the key is in the on and start postions and remains on after the car starts and moves.

What's been tried so far without success:
1) Inspected and cleaned all four wheel sensors
2) Cleaned the sensor rings
3) Visually inspected sensor wiring from sensor to where it enters body
3) Inspected the over-voltage relay, the silver metal cube above the ECU, fuse wire inside was intact, tested continuity with meter
4) checked fuse in main fuse box
5) removed, inspected, and reseated relays in the ECU fuse box, no electrical testing

From reading, it seems this issue is a ECU system fault and not a sensor related issue.

What's next?
1) I can check power to ECU
2) Is there further testing or taking measurement before swapping parts?
3) Seems like there isn't much more to probe as it all feeds into the ECU that controls the dash light.

[82eye]

From reading, it seems this issue is a ECU system fault and not a sensor related issue..

e30 abs is independent of the ecu. it has it's own stand alone module.



number 14.

edit : to test a bad sensor. unplug each sensor at the wheel one at a time, when the abs light goes out, you've found the bad one.

[PEZ2]

Check part 13 in the diagram above. It has an internal “fuse” to protect the abs brain , item 14 above. All of which is under the dash left side.

[windtrader]

@Pez - i did check the over voltage relay, part 13. fuse is good.
82eye - I will test each sensor but ECU is very expensive to swap for testing.

[PEZ2]

Only other item I can think of, is what the cause for my 86e light to be on. I thought it was the fused relay since it was blown, but it turned out that mice had chewed the power delivery line to the abs pump. On early cars the abs is a separate “ add on harness” and the damage was where the power line crossed under the fuse box.

[windtrader]

waiting for replacement ABS control unit. will advise once swapped

[windtrader]

Swapped the ABS control unit, did not fix the light on issue
Tested each wheel sensor for resistance, all measure around 960 ohms
Rechecked the fuse in part 13 (the relay clipped to the control unit, fuse intact
Pulled the fuse cover of the ABS unit, pulled and inspected visually, look fine.

Next up is to get the wiring schematic for the control unit plug and check the wiring from the sensor the the control unit.
Replace ABS fuses?
Starting to run out if ideas.

[windtrader]

Still no joy on getting ABS dash light to go out.

The sensors check OK
The sensor wiring to the control unit plug are OK
The overvoltage relay is OK
The ABS control unit is OK
The ABS hydraulic unit sensors visually look fine.

Based on schematic not sure what else needs checking.

ideas?