Was in the process of prepping car for Mot after the car being laid up (inside nice warm garage for six months) took out for a road test and noticed the ABS warning light hadn't gone off and testing the brakes showed the ABS did not operate although the brakes are strong and otherwise ok. The car had been working perfectly prior to being laid up and it is only the ABS light that stays on. Brake fluid level is ok, no sign of damage to any of the wheel sensors or wiring. I'm puzzled as to where the problem could be. Would the first obvious source be the accumulator? Any way of testing this unit?

 

Quickest way to find out is to read the ABS codes. Jumper the 3 pin connector on the drivers side of the boot and read the codes. Takes 2 minutes

 

Do you have a vacuum booster or hydraulic accumulator brakes. 95 can go either way.

If you have the vacuum booster type you will need the pecus diag tool because there is no onboard way to get the trouble codes. It is still possible to self repair using the process of elimination by reading continuity values of the 4 wheel sensors and the brake switch. You will need patirnce and a witing diagram. If all 4 wheel speed sensors are good, brake switch tests ok and the there is ground and +12v everywhere it should be then you need a new controller. The controllers often fail because of a weak solder joint at the motor connection. You can cut the plastic and resolder or Source a new part from a breaker.... but 3 of the last 5 I bought needed repair. The other 2 havent been checked yet.

If you have the hydraulic accumulator style then it can self diagnose.

 

Thanks for your reply, very helpful. My system is the hydraulic accumulator type and there is an obd diagnostic socket under the passenger footwell but I would need to take the car to an auto electrician to read the fault codes, if any as I don't have a reader. I did try disconnecting the battery and the abs warning light went out and for about 10 minutes driving and testing, everything worked including the abs. However, the warning light came back on again and this time won't reset by battery disconnection. I presume when you say 'controller' you mean the abs ecru located in the left side wheel arch in the boot/trunk? Have you any photos of the ecu showing the particular bad spot you mention?
thanks again, Ian

 

I had the ABS light always on in my '93. Turned out I had a bad frayed speed sensor cable to one of my front wheels. Replacing it fixed my problem. I believe the cables functionality can be tested by checking with an ohmmeter. Warning, they are expensive, between 390.00 and 515.00 depending on your source.

 

long story short - ended up with a 3 month on and off complete brake system overhaul including a brand new abs valve block (extremely good luck to find one) master cylinder seals, o-ring kit, new callipers, discs, pads front and rear including flexible hoses and a replacement abs ecu just in case it was being troublesome. and obviously a complete bleed of the system. Result - the car is transformed - no more abs warning light. brakes as as good as straight out of the factory. but it was one hell of a job which took a massive amount of effort to be completed by me on my own.