Does anyone know how to test an ABS ECU from '91 940?

Come on guys! Somebody's got to give me a brilliant idea about this constant ABS light, or I may have to hold back on saying to everyone that the Brickboard is the best car, any car, forum in the world! ???????
I haven't been defeated by a Volvo yet, I don't want to ruin my record!

Dear tedv,

Hope you're well. I suggested you check the wire harness that goes to the sensor in the differential housing.

You can check this harness for damage, if you have the means to raise the car's rear end far enough to allow access. Be sure to use jackstands or - if you don't have jackstands - to put solid supports (blocks of wood, cinder blocks, etc.) under the tires. With such supports in place, you can safely go under the car.

The wire harness - that goes to the sensor in the differential - is exposed to road hazard damage and to the weather. It is a more likely source of failure than other parts of ABS system wiring.

Hope this helps.

Yours faithfully,

Spook

Well, I went under the car, and the SE is nothing like a non IRS 940! I seriously doubt that much can be done without a hoist since the suspension has to be dropped to access or even see anything: even the differential fill hole is invisible, as are the sensors for the speedo and ABS. The FAQ doesn't address any of this so I guess I have to pay a visit to my favorite mechanic.

Have you looked through the FAQ's?

http://www.brickboard.com/FAQ/700-900/BrakesABS.htm

Dan

Hello
what is your problem specifically?
Mike

ABS light ON steadily and continuously, always, when the car is running.
I have checked the wheels sensors, changed/checked fuses, relays, ECU (used), wiring appears intact... Have nOT looked at the rear end yet....

Dear tedv,

Hope you're well. I can't recall a post reporting a failure of an ABS control unit.

The problem is more likely to be a damaged wire. I do recall posts reporting chafing of wires from the differential to the instrument cluster. Inspect the two wires that connect the speed sensor (in the differential housing) and the instrument cluster.

It is possible that someone doing work on the underbody - or behind the dash - damaged a wire. That damaged wire causes the ABS system to sense an open or shorted circuit.

If all of the wires from sensors to the ABS unit are in good shape, then it may be time to think the ABS control might be at fault.

Hope this helps.

Yours faithfully,

Spook

I haven't looked at the atrear end yet. I have a control unit but it is used so that's why I'd like to know how to test it. I guess I'll swap one from my other cars to test.