1998 S70 ABS speed sensor wiring

[volvofrik]

This is my first post on the subject but I have seen other Volvo fellows debating the same issue but I have not found the answer I am looking for. The car in question is a Volvo S70 1998 manual transmission 280,000 miles.
I have a problem with the Front passenger side ABS speed sensor. After changing the sensor which appeared to be faulty, my mechanic tells me now that there is an open circuit on that particular senor. When I recently changed the sensor I noticed that the connection to the sensor was not the original one but the two wire were connected with a crimping connector. I decided to buy an original Volvo wiring harness and attempt to replace the existing one. Surprise, easier said then done!!
I intended to connect the new wire to the old wire in a convenient location, with the intention of using as much of the new harness wire I could. Unfortunately the old wire seems to disappear under a computer module (positioned in front of the engine compartment next to the windshield wiper refill pipe) and enter a plastic ducts with other wires. Am I correct so far?
Has anybody try to do the same or shall I just resign myself to connect the two wire (splicing/soldering,insulating etc.) in the wheel well and using about a foot of the new wire?
Thanks for any support and ideas.
PS: I don't have access to a lift or a safe sets of car stands to be able to work safely from under the car but I could borrow them from a friend if necessary

[Ozark Lee]

The routing of the sensor wires is from the wheel sensor to the ABS module on twisted pair wires. Have you used an ohmmeter to check the wiring from the ABS module connector to the sensor? I'm not sure how the determination of the sensor being bad was made but if it was done via a scan tool then there is decent chance that the sensor and its wiring are OK but the ABS module is bad.

What fails on the ABS modules is the pins from the connectors. The solder joints crack at the point where they were originally soldered to the PC board on the module and when the joints fail the module can give what are actually false sensor errors. From the module's perspective it sees an open circuit and posts the error code as it should but in reality the open circuit is inside of the module itself.

All S70 ABS modules fail, it is just a matter of time. They can be rebuilt for under $100.00 and once rebuilt they stay fixed forever. If you are handy at soldering and have a good sized soldering iron you can rebuild it yourself. I have a writeup on how to do it in the repair database.

If you aren't that adventurous Midwest ABS is as good as they get.

https://www.midwest-abs.com/ABS_Modules.php

...Lee

[volvofrik]

Thank you for your answer. I guess I failed to mention that I replaced the ABS module with a remanufactured one provided by Midwest ABS, from whom I have received great assistance and service.
The sensor I removed was completely covered with many years of dust, grease etc. So I thought it was good to change it anyhow. So my problem is just the wiring, hopefully. But as I said I didn't expect to be so difficult to have a decent access to it. By the way, after installing the new sensor, I even switched the sensors from right to left and then the reset the ABS module. The left side was OK the right side was giving "open circuit".

[sleddriver]

Thank you for your answer. I guess I failed to mention that I replaced the ABS module with a remanufactured one provided by Midwest ABS, from whom I have received great assistance and service.
The sensor I removed was completely covered with many years of dust, grease etc. So I thought it was good to change it anyhow. So my problem is just the wiring, hopefully. But as I said I didn't expect to be so difficult to have a decent access to it. By the way, after installing the new sensor, I even switched the sensors from right to left and then the reset the ABS module. The left side was OK the right side was giving "open circuit".

Please update us. I have the same year.

[as400jockey]

Most if not all of my Volvos (97 850; 98 S70; 98 S70 T5; 01 V70 T5) had the failed ABS controller. But the 97 and 98s had another frustrating issue. The connector at the wheel speed sensor fails. The wire detaches. In 99 and beyond they changed the connections to the sensor includes a cable. In 98 and prior the wire is 'permanent'.

Since you can't find any more 'pigtails' for this, you need to MacGruber a solution. I was able to remove the connectors from the shell and solder in new wire, then splice that wire to the existing 'permanent' harness.

An unfortunate design. A real PITA.

Before taking anything apart - remove the connector from the ABS controller. Get a couple small paper clips and a multimeter. Look for about 1000 ohms across the four pairs of leads that go to the four wheels. Look for a pinout diagram. You may find one circuit is open - no resistance reading. That's your problem child.

Good luck.

[as400jockey]

the part number that can no longer be found is volvo 9442888