Re: ABS cutting in too soon
Well I've got it fixed at last. After months of investigation; testing with an oscilloscope, swapping over sensor leads, paying for parts that don't arrive, sending components away for testing, there still appeared to be nothing wrong. Then a Bosch specialist garage managed to find a faulty ring on one wheel. It needed a new hub.
If anyone has similar problems here are a couple of points that might help. The rings that the sensors take speed signals from don't have protruding teeth. I spent ages looking through the hole that the sensor plugs into trying to find them. They're inside a molded ring. Also, you can't measure the output from a sensor by disconnecting it from its socket and connecting it to a volt meter. The sensors only work when they are powered up by the ABS ECU, so you have to connect an oscilloscope in parallel with the sensor to see what's happening.
Anyway, now got a fully working 156 again!!!!!!