1999 V70 ABS. ECU is fine, what next?

[jamlip]

Hi all. I have a 1999 V70 with an ABS light showing. It was initially intermittent but is now permanent.

I had the ECU checked-out by a professional and it tested fine, so there's something else amiss.

Diagnostics says two things; front left wheel sensor and also ABS pump. Specialist said he's never known a pump to fail, so unlikely that. I checked front left wheel sensor with a multimeter and the resistance is the same as the front right sensor...

Anyone have any ideas before I put a brick on the accelerator and punt it into the sea?

[leec70]

from what i have seen on the forum and speaking to a volvo tech i know there is a common problem that the abs ecu suffers from dry joints and shows faults elsewhere in the system when it is at fault. had a search on here andsounds a relatively easy fix

http://www.volvoforums.org.uk/showth...ght=abs+repair

http://www.volvoforums.org.uk/showthread.php?t=72655

[jamlip]

Thanks for the reply, but it's been checked and it's OK.

[GEORGEROV]

Assuming the sensors are ok then next check would be the wiring from them to the ecu to make sure the ecu is receiving the correct info.

[upv5]

During 1999 the type of sensor was changed, the later one cannot be checked with resistance.
You have to connect a voltmeter from earth to the sensor while it is connected to the ECU and ignition on. One sensor wire will read battery voltage i.e. 12V, the other wire will show a rise and fall of 1V as the wheel is turned, from memory it was 9.5 to 10.5V
All this is detailed in Vadis but not easy to find.
If you have a Haynes then the wiring diagram contained will not match the wiring on your ECU plug on later 1999 motors.
If you have the earlier version a better check for the sensor is a Voltmeter set to millivolts AC connected across the disconnected sensor, as the wheel is turned (at least one rpm) you should see a reading 0V to 150 mV.

John