I've had a problem with the ABS warning lamp lighting up after moving off. So far I've done most of the "easy" (cheap!) checks - cleaned sensor rotor and sensor heads, checked wiring, changed fluid etc.... both the front sensors checked out the same - no short circuit to earth and the same resistance reading for both, somebody has suggested though that both these sensors may be shot - what I'd like to know is what are the correct values, and what is the proper method for checking them?.....

Mac

Just sorted out my ABS light problem (89 740).

Turned out to be the wire from the rear sensor (Diff) having broken in the sleeving. Somtimes light would come on immediately; sometimes after a few yards; sometimes not for miles!

Check with a meter and be sure to give the wires a 'waggle'.

Good luck as anything else is expensive!!

Andy:

I too had very intermittent ABS failure light for the last six months, I assumed it was gunge on the ABS front wheel commutators, which I had about 3 years back. Then it went totally and BIG SURPRISE my speedometer quit working. The sensor feeds both ABS and speedo. I never noticed the speedo failing as it was only a temporary break in the circuit It turned out both wires were broken at the differential sensor plug, but would still make occasionly. They were broken by fatigue not corroded, I replaced the connector and then put RTV at the connector wire junction to reduce the strain at the abrupt change from wire to where it goes into the connector. My first break was at 304,000 kms and almost 11 years... with my improved strain relief I figure I am good for at least the next 500,000 kms and 15 years. This is a rather minor design fault. It might be worth it for anyone to just add a bit of RTV at the junction of the wires going into the connector at the differential. This is for models with ABS for sure and may apply to some non ABS but the non ABS I checked in the wreckers did not pick up the speedo from differential.

Sheldon,

Yes - that was EXACTLY the scenario with my ABS light. By chance I noticed that the speedo 'blipped' as the ABS light came on the other day. checked the wires and both had flexing breaks. Remade the wires and bingo - problem solved. Strange that the Speedo kept working all the time - I guess the ABS computer is a bit more sensitive.

Wish I'd seen this before I replaced the one remaining 'old' sensor at a cost of 125 UKP!

Hope that's the problem for original poster.

Are your sensors square or diamond shaped? If square change the sensors. Any DTCs?

George