Hi everyone

Car is a 1990 900T. ABS light is on. Tech II does not communicate with this MY and I have been unable to track down anyone with an ISAT.
This is what I have done so far:
Pump was dead so I replaced it with a known good unit. The pump, after some initial crankiness, pressured up and runs fine. I bled the unit. Light still on. I switched out the relays, plugged in a different ECU I had on the shelf and disconnected the battery for a while.
Light still on.
I am now assuming it is a wheel sensor. However, I am unclear as to why I would have a intermittent hard pedal ( some days pedal is normal) with a wheel sensor fault tripping the dash light. The pedal was not hard or weird feeling with the old non-functional ABS pump?? It felt like a non-abs brake pedal would.
I have not figured out how to fault code manually, the supposed two-pin connector located behind the coolant tank seems to be not there. There are two grey connectors back there but they are plugged in to something, they don't seem to be add-ons to the wiring harness.

Does anyone have any thoughts on this for me? To remove and replace wheel sensors one by one is so time-consuming and cost-prohibitive. I am sure they are very rusty.

Thanks,

PS. Does anyone know anything about the 'diodes' located under the relay box?

Take a look at the ABS related pages here (http://townsendimports.com/Web/brake_folder/brake_docs.html) for help with diagnosis.

I wouldn't expect a sensor to cause a problem with a hard brake pedal. That sounds like the pump may not be running on occasion (on the ABS system it is dependent on the pump as thre is no vacuum servo assistance).

Ultimately don't rule out a problem with your battery. Sounds daft I know but if it isn't in peak condition it may not be smoothing the output of the alternator properly which causes interference to the ABS ECU. I spent 2 years chasing an intermittent fault light before finding this out...

Hi,

Good luck for your problem !

It's difficult to find dead stuff on the ABS ate system without SAAB diag ABS, in France it's impossible to find it !
But on the peugeot 505 turbo there was the same ABS system, and i found the whole diag without need SAAB electronic tools.

It help me to find my dead part, because the diag code was crazy ....

I hope that help you : http://www.saabcentral.com/forums/showpost...mp;postcount=31 (http://www.saabcentral.com/forums/showpost.php?p=1586049&postcount=31)

If it is a wheel sensor causing the light to come on all you need to do is get one replacement and plug it in, in place of each sensor in turn and turn on the ignition. All the system is looking for is four good sensors, if it has four good ones the light goes out.
The easiest connections to get to are the rears which are under the rear seat, unplug one of the sensors and plug in the replacement, turn ignition on, if abs light stays on reconnect the fitted one and move on to the next.
Alan

ABS, again.
I took apart and cleaned the wheel sensors in the rear and they looked fine, not rusty at all. Also, I seemed to be getting good multimeter readings both front and back. Unfortunately, now the pump I put in has stopped working. I am assuming it quit the day I experienced a scary hard pedal in close traffic. Since it was a perfectly good working unit when i pulled it out of the 93 MY I had as a parts car, i had not checked it to listen to it running.... But, it is dead. It ran only a few days, maybe 100 miles.
I do not look forward to changing out another pump, I will have to find another used one somewhere. It was about a 6hr job.
Does it seem strange to anyone for a working pump to quit abruptly?
So I am driving around with marginally functional brakes.

Any things I could look for that would have shut down the pump? ( besides the obvious - fuses)

Thanks folks!