Abs unit

[Laird Scooby]

Originally Posted by Ian21401

Very helpful Dave, should the need ever arise I will refer back to this.
When I needed to renew the FOS sensor I had to destroy it. It came out in several pieces. The replacement was a Bosch ( 0265001231 ) obtained through my local Bosch agent, rather than my Volvo dealership. £54.58. For items such as that, ( eg lambda sensor, ) if I can find a Bosch part number I usually check with both the Volvo and Bosch dealers.
For the record, whilst tracing the fault I noted the resistance of the “good” sensor in the FNS as 1,080 ohms. The resistance of the new Bosch sensor was 1,093 ohms. I believe that the spec. 900 ohms to (not sure).

The resistance on my good sensor was about 1180 Ohms and on the failing one, 1043 Ohms Ian.

As long as the resistance is in the range of 800-1600 Ohms, you can normally (there are exceptions) assume the sensor in question is ok. I've known several sensors to be in that range and still working satisfactorily but as detailed above, the failed one on my 760 was not working properly!

There's no real need to go for Bosch sensors on the ABS system, it's used by many other cars as well (including my Rover so i've already had plenty of experience on it. )

In fairness, the Rover uses the ABS 2E system as fitted to later 940s, earlier Rovers (from 86 to 92) used the same Bosch ABS as the 7xx up to 1991/2 and early 9xx to that date.
It leads me to believe the ABS-2E was launched in 1992 by Bosch as Volvo had already changed to 48 tooth reluctor rings on the wheels before that point (around late 1990-91 as far as i can work out, it was a VIN number change point though and i don't know the number but can probably work it out) and with it came a change of ABS ECU, the later ABS-2E ECUs aren't compatible with the earlier system and the main differences i've found (there may be more) on the earlier ECUs are the later one is set up for 48 tooth rings and the earlier one for 96 tooth rings. They are swappable, i now have a 1991 ABS ECU in mine for the 48 tooth rings. If i put the original one back in, instead of not showing any faults from sensors not giving a signal until 8mph, because it's expecting twice as many pulses, it won't show a fault until about 15mph. On the original 96 tooth rings, obviously it shows a non-signalling sensor at 8mph.

[griston64]

Lovely looking ABS rings there Dave

[Laird Scooby]

Originally Posted by griston64

Lovely looking ABS rings there Dave

Thanks Mark - bit of an improvement wouldn't you say?