94 854 Turbo - ABS/TRACS error code 422

[Volvofan94]

Hello MVS,,

This past weekend my area received a lot of rain from a storm that passed through. Unfortunately I was on the road when the storm came in and the rain started. My Volvo did fine going through the water covered roads, but today the ABS/TRACS lights came on with error code 422 - Rear wheel return valve circuit, open/short. I'm guessing one or both of the rear ABS wheel sensors is either shorted or not working anymore (more research to come on my thought).

I tried to reset the ABS codes, but the 422 code returns right away when I start the car again.

Did some searching on the Internet and found a good guide (link attached below) which gave me a better idea more about the 422 error code and how to test it. I don't have a test box though to actually perform the test. Would it be possible to use an Ohmeter to test each rear wheel sensor from the ABS module plug or is the test box required?

http://www.volvotips.com/index.php/850- ... ce-manual/

Has anyone come across this ABS-related issue before and fixed it?

Thoughts and suggestions are appreciated!

Thanks everyone!

[Ozark Lee]

The stuck valve error is usually a problem in the ABS control manifold, not the sensor. You might want to give the ABS manifold block a smack with a hammer and see if it will free up the valve. When was your last brake fluid flush? Your error is fairly rare but I suppose rusty brake fluid could gums things up.

...Lee

[Volvofan94]

Thanks Lee - I will try to smack the ABS pump module with a hammer this evening and will post back the results.

When I bought the car last March the brake fluid looked clear, like it was recently flushed. I haven't done a brake fluid flush on the car myself since I've owned it. Would driving through the heavy rain cause water to get into the pump? I do remember my brakes feeling a little firmer when I drove the car the next day. Also, it's interesting the error code didn't appear until two days after the rain storm.

[Volvofan94]

I tried to tap the ABS control module with a hammer, but no success. I didn't remove the air box and intake because the engine was hot. No luck. Going to try again later this week when the engine is cooler, but remove the air box and intake pipe for better access next time. Hopefully it will free up again and clear the error code.

I'm thinking I may need to find a used TRACS/ABS module from my local pick and pull if the hammer method doesn't work. There is dirt and grime on the brake line fittings like brake fluid was leaking out of there before. If I can't find an ABS/TRACS module locally I'll post something up in the classified section!

I'll keep everyone updated on my progress. Hope I don't have to replace the ABS module!

Any thoughts or additional suggestions are appreciated!

Thanks!

[Ozark Lee]

The older style systems are plentiful and cheap. You don't just need the module, you need the entire setup. and you will need to do a thorough bleed job after you replace it. If you search ebay you will find dozens of them.

...Lee

[Volvofan94]

Thank you again for your help so far Lee!

I'm in the process of finding a replacement ABS/TRACs pump. Is there a preferred method to remove the old brake fluid from the master cylinder reservoir and ABS pump before I take it all apart? I've seen forum posts on how to refill the system with fresh new fluid.

[Ozark Lee]

I use a turkey baster to suck out what I can. Be very careful with brake fluid, it destroys the paint on the car immediately on contact.

Oh, and don't try to sneak the turkey baster back into the kitchen after you use it.

...Lee

[Volvofan94]

I finally got around to replacing the ABS/TRACS pump this afternoon. The job took me about 4 hours from start to finish, but it's nice not seeing the ABS/TRACS lights on all the time.

A tip if your Volvo 850 has the 422 error code:
Before I removed the ABS/TRACS pump I tested the replacement one by unplugging my old one and connecting the replacement. There are 3 electrical connections to disconnect on the old ABS pump before connecting the new one. One is on the top of the driver's side shock tower, the other two are the power connector and relay control wires on the ABS relay. Connect all these to the replacement pump to test it. Since I didn't want to drive the car, I reset the error code then turned the ignition off then to Position II. Reread the codes and 111 appeared and the TRACS light went off. A result - yes! After that I felt comfortable the replacement unit was a good one and I could go through the work to replace the pump.

Hope this helps!
-volvofan94

[Ozark Lee]

Well done!

...Lee