ABS warning light nightmare!

[ValW]

Hi guys! So today my Puma wouldn't start (It's a 1998 1.7). The AA guy came out and after about 30 minutes of tinkering figured out the fuel pump fuse had blown. So he replaced it and the car started (yay). I started driving home and noticed the ABS warning light and traction warning light were both on and it was idling at 3500rpm. I replaced the throttle sensor which sorted out the idling problem. I rebooted the ECU by disconnecting the battery for 30 minutes etc and that didn't work. I took it out to test emergency braking and the ABS did not kick in and I managed to skid down the road (which it would never normally do). Any ideas? I checked all the fuses and they seem fine and have checked one of the front ABS sensors and it isn't dirty. The only thing is at the MOT test place it nearly failed on the rear brakes even though I had the rear cylinders replaced two months ago so I'm guessing those sensors could be dirty? Or maybe a loose connection or something??

 

[Mustardmit]

One of the sensors has probably gone phut. I had the same problem and found out the hard way that it was an MOT failure.
I checked the impedance of both front sensors and one of them (driver's side) was suspect. I bought a new one from Euro Car Parts for £50, bashed the old one out and replaced it, then bingo! The characteristic crunching sound of the self test at 15mph (or whatever it is) and the light on the dash went out!

 

[Mustardmit]

...I forgot to say, the problem was two-fold. The wires between the two rear sensors had been "bodged" together by the previous owner and had come apart (they were twisted together and bound up in tape).
15 mins with a gas soldering iron, a head-torch and some heat-shrink sleeving sorted that one out.

 

[ValW]

Cool, I'll check the sensors then. How did you check the impedance of the sensors?

 

[yippeekiay]

Use a multimeter on the sensor side of the connector. Doesn't matter which probe you put on which terminal of the front connectors but if I remember correctly (probably not), I think there was 4 terminals on the rear connector so a bit of swapping here and there until you get 2 that give a reading will establish the other 2 for the opposite sensor. They should read around 1 ohm for all sensors. If it reads zero it's kaput.