ABS Light on in 1998 volvo S70



I am just about to sell my 98 volvo and the ABS light is on intermittently. The fix-it guy said that the module fails gradually and and it’s $639 to fix.

Well that’s a lot for a car I’m selling very soon - how would a rebuilt/salvage/etc. module be? A local mechanic said they are hard to find, and the Volvo’s only place down the street won’t install anything but Volvo parts.


The light will come on for many reasons, only one of which is a bad control module. A bad wheel speed sensor will turn the light on, as will a bad electrical connection somewhere in the ABS system. Get another opinion, or a system diagnostic, before you spend all that money.


The fix-it guy said that the module fails gradually and and it’s $639 to fix.

Why does he think it is the module? It is possible, but it sure would not be first on my list, I think you need a new fix it guy. A 1998 car should give you an error code if there is a problem. I would guess it should show up on a standard scan

You need to have the codes read. Some places will read them for FREE. Try Autozone or Advanced Auto Parts. Get the exact code not just their translation into English and post it back here. It likely will have a format like P1234.


[b]You don’t want to replace an expensive ABS component unless you’re absolutely positive that’s the problem.

The most common cause for the ABS light to come on is because of a problem with one of the wheel speed sensors. And there’s a way to determine this.

When you first start the vehicle, the ABS performs a self-test. If the hydraulics and electricals are working correctly, the ABS light goes out. If however the ABS light comes on after the vehicle starts moving, this usually points to a problem with one of the wheel speed sensors. This is because the ABS computer isn’t able to measure the wheel speed sensors signals until the vehicle is moving.

The most common reason for wheel speed sensor problems is with the tone rings. The tone rings are metal toothed rings that rotate under the wheel speed sensors. And the teeth on the tone rings are what provide the signal to the wheel speed sensors. Over time, debris can form in between the teeth of the tone rings. This debris can be metal dust from the use of semi-metalic brake pads. And when the gaps between the teeth of the tone rings accumulate enough debris, it can mess up the signal to the wheel speed sensor. Which in turn causes the ABS light to come on.

So, have someone inspect the tone rings for debris. And if any is found, have the tone rings cleaned with ABS safe brake cleaner. At the same time have them unplug and plug back in the wheel speed sensor connectors to ensure that there’s a good connection.



Thanks for the advice. The light does stay on when the car’s started up and not moving. I usually go to a Volvo specialty place down the street and they hooked it up to the computer; that’s where I got the diagnosis and the giant estimate.

So although I will certainly have the wheel speed sensor and tone rings checked, it looks like I may be back to the ABS module replacement. I have seen some on the internet for much less. What do you think? Thanks for your opinion! Diane


Presuming the control module is electronic, I think it’s unlikely (but possible) that it would go bad “gradually”.