1998 S70 GLT - ABS light and Speedo issue (Not ABS module)

[clarkerussell]

Hello everyone,

My ABS light is coming on intermittently and my speedo sometimes doesn't work. Knowing this was a common ABS module failure item, I sent my previously rebuilt module to Midwest ABS repair. He checked it out and it had no issues and no stored fault codes. Reinstalled and the symptoms continued...

Assuming the next issue was ignition switch, I replaced the electric portion with a new Volvo part... Still not fixed.

I'm hearing this is since both the ABS module checks out fine and the switch has been replaced, the likely caused by a power related issue between the cluster and the ABS module. Unfortunately I can't find any "next steps" to proceed with the troubleshooting.

Does anyone have any further suggestions? Thanks in advance.

Clarke

[scot850]

Have you checked your ABS cables and connectors for continuity and resistance as well as the reluctor rings for rust damage or cracks?

I would check the front for this over the rears as with a bad or no signal it will take out your speedo as well as that is where it gets its speed signal from. Be careful with the ABS cables as they can look ok but be broken internally.

Neil.

[surfbug1]

Interested in how this turns out.

I have the same problem, but have not sent in my ABS unit yet.

Speedo will work some days, and then nothing for a few days weeks kinda thing.

And the ABS light comes and goes with the speedo working.


I'm gonna chase the abs cables...what is the reluctor ring?

Other than replacing the ABS cables, how do u check if they are cracked on the inside?

[scot850]

The reluctor ring is the toothed ring on the outer ends of the axles. The ABS sensors look for the gaps in the teeth to know if the wheels are moving at the same speed, but also use them for reading the car's speed. They can corrode, fill up with debris, rust so teeth cannot be differentiated and also crack. All will cause issues for speedo and ABS even if the sensors and cables to the ABS are good.

Neil.

[BEJinFbk]

https://midwest-abs.com/troubleshooting

Good stuff about simple sensor testing
towards the bottom of the linked page.

[abscate]

Is there deep knowledge on which sensor is used for speed input to the speedometer? I recall a UK document had this

Reluctor ring, also commonly called a tone ring

[surfbug1]

Ok cool. That helps.

The speedo works sometimes, but the abs light won't turn on and off with that little switch on the dash! Or is that a traction light ..."TRACS"

that thing won't switch on and off no matter what.

Defe the abs module? I should send it out?

[abscate]

ABS is always on, the TRACS light turns off the traction control system only, it turns back on by default on startup

Talk to mattymoo (email or phone) about your symptoms. I’m still trying to relearn how the speedo gets it data

Inspect your front abs sensors and wires for any damage. Replace anything that isn’t pristine.

[Matty Moo]

Anything errant coming from any of the wheels that is enough to cut out the speedo would have set an absolute minimum of two codes, which would be open circuits on both front wheels.

With your regular faulty module you would have an absolute minimum of nine stored codes to reach that point, but the usual is 13. an extrapolation/wrong wheel speed code for each wheel plus an open circuit and one speed signal code.

Anything causing no speedo but with no codes is going to be communication. No power would usually set an internal relay code on a 96-98. This almost always leaves either the ignition switch or the link between the module and cluster.

Then from there we can add other nonsense that frequently pops up. 99-2000 clusters installed in a 98 or vice-versa, drunken "master mechanic" uncles that "touched" something. Missing grounds, some rigged trash electrical work, aftermarket wheel sensors, etc.

There's about 10 other things I'm missing.

[clarkerussell]

Can 850OBD-II program pull ABS fault codes?