ABS issues

98S70T5 · Post by **98S70T5** » 25 Nov 2019, 07:44

Guys, the ABS light started coming on a week ago in my 98 S70. At first it wouldn't come on until 5-7 mph or so. Now it's just on solid. I was hoping it was a wheel speed sensor based on that. The front two ohm tested ok but it looks like the rears have long wires that go up inside the car. I took the pass through plate off that's over the fuel tank lines (maybe pump). Didn't see a plug there but ran out of time before I could take the passenger side trunk panel out to chase the wires further.

Just looking to see if I am barking up the right tree for the location of the plugs for the rear wheel speed sensors. Haven't been around a OBD tool to hook up and check the ABS codes yet.

It's starting to make ABS noises if you turn fairly spiritedly at 10-20 mph while on the brakes in either direction now.

Post by **abscate** » 25 Nov 2019, 08:08

There is a parts change around 1998 when the rear abs harness went from two wires to a one wire harness

You will have to confirm part numbers by comparison or by VIN

I did a DIY with pictures in my 1999 T5, the thread is referenced in my maintenance thread, forum link in my sig

98S70T5 · Post by **98S70T5** » 25 Nov 2019, 08:23

Cool, thanks for the info. You can see two harnesses going up over the rear axles and disappearing.

98S70T5 · Post by **98S70T5** » 06 Dec 2019, 06:00

Just tested my rear sensors last night. They are within ohm range and show fluctuation when spinning. Going to need to grab up a code reader of sorts. Hopefully its just a bad wire but my luck its likely the ABS brain/control.

Every once in a while while stopping moderately the car would click in the brake pedal exactly once a second until the car got below 10 mph or so or you let off the brakes. I assume this was it telling my it was on its way out.

Post by **scot850** » 06 Dec 2019, 08:01

If it is the ABS module (very common particularly on turbos due to location above the turbo heat) our MVS frined Matty at Mid-West ABS is the man specialising on these Volvo ABS units. Go to his web-site for lots of info.

Neil.

98S70T5 · Post by **98S70T5** » 06 Dec 2019, 10:29

Thanks for the info! I will get with him when I am ready to repair. Currently burnt out working on this rig. It's constant.

Post by **abscate** » 06 Dec 2019, 10:36

The system self tests at low speed, so that might explain the coming on at 5-7 mph. I thought it is a bit faster on mine, like 10 mph, but you can hear the brrrrrp sound when it self test if the radio is off, and the muffler good.

If you get enough failures it will latch and hold an ABS code and stay on, though,

Get a code reader that can read ABS codes and it will point you in the right direction.

bcfischer · Post by **bcfischer** » 15 Jun 2023, 19:19

abscate wrote: ↑06 Dec 2019, 10:36 Get a code reader that can read ABS codes and it will point you in the right direction.

I just replaced both front sensor rings (completely rusty and crusty) and wheel speed sensors while changing out the control arms and hubs. I am still getting the ABS light and a 1550 code. I am probably going to have the module repaired, but wanted to be able to verify operating status of the wheel speed sensors as they are new. ABS has long been an issue and I get the buzzing while braking.

My current code reader will read the 1550 but not live data from each wheel. I am considering upgrading to a Zurich 11s that says it reads ABS. Does the OBDii interface on a ‘99 V70xc output individual sensor readings to a reader that can read them, or only throw the codes.

If as an alternative, if I ohm tested a sensor, what would be the difference between an operating sensor and a shorting/unconnected sensor?

Brian

Post by **scot850** » 15 Jun 2023, 19:28

Have you checked Mid-West ABS's help page for diagnosing issues?

Neil.

Post by **wizechatmgr** » 15 Jun 2023, 19:57

bcfischer wrote: ↑15 Jun 2023, 19:19
abscate wrote: ↑06 Dec 2019, 10:36 Get a code reader that can read ABS codes and it will point you in the right direction.
If as an alternative, if I ohm tested a sensor, what would be the difference between an operating sensor and a shorting/unconnected sensor?
Brian

Yes, you need to test them this way as well. There are known resistance values.

A single click per revolution could also be CVs that are slowly nearing their end of life or or a wheel hub on its way out.

For giggles, check and verify your axle nuts/bolts are tightened to spec.