ABS Module or Wheel Speed Sensor?

[matthew1]

Hi. This is my first post, and please excuse me if I'm asking something that has been answered numerous times before. I have a '99 S70 GLT with the notorious ABS malfunction, giving me a P1550 (wheel speed sensor) code. From what I've read, the controller is almost always the culprit, but I just wanted to make sure before I spend any money.

When the ABS unit goes bad, will the speedometer and odometer always malfuntion? I seem to have all of the symptoms except for that. My Cruise Control stops working, ABS and Traction lights come on, the transmission seems to shift differently, the RPMs take much longer to come back down... But I've also had the ABS kick in when it shouldn't, just under normal braking conditions, and I've heard this is more of a sensor issue, but I could definitely see that also being a controller issue. Thanks for any help!

-Slumbo

[matthew1]

It's very rare that it's the wheel sensor. Matty Moo has done 700 ABS module rebuilds, and his prices start at $55.

At that low of a price it's a good way to troubleshoot this, because if it's not the module, it will be soon.

[Jot]

1550 is a code for one of the front wheel sensors. I was able to use an ohm meter to find which one was bad. The wire harness can be unplugged and tested without removing the sensor . When I found the one with an open circuit I tied on a string before pulling it out from the bottom and used the string to pull in the new one.

[geokilla]

I'm experiencing similar symptoms as well and I'm pretty sure it's an ABS Module problem. I'm going to order an ABS Module from Matty and hopefully everything works again.

http://www.matthewsvolvosite.com/forums/viewtopic.php?f=1&t=48767

[Matty Moo]

1550 is a code for one of the front wheel sensors. I was able to use an ohm meter to find which one was bad. The wire harness can be unplugged and tested without removing the sensor . When I found the one with an open circuit I tied on a string before pulling it out from the bottom and used the string to pull in the new one.

Kinda-sorta... P1550 is just a regular p-code that says the tcu isn't getting a valid speed signal from the abs module. The tcu tells the ecu to set the light, but to figure out which one it is you have to do either what you did or scan.

It's very rare that it's the wheel sensor. Matty Moo has done 700 ABS module rebuilds, and his prices start at $55.

At that low of a price it's a good way to troubleshoot this, because if it's not the module, it will be soon.

As of today I'm right around 2000 altogether. 1557 of them were exchange and somewhere around 400 were mail in repairs. There's a handful I did when I first started before I kept a yearly spreadsheet that aren't in there.

The amazing thing is that 80% fo the people I deal with have zero idea about any of the Volvo forums or are enthusiasts.

[Slumbo555]

I'll be ordering an ABS module today after I doublecheck the part numbers to make sure I'm ordering the correct one. Hopefully I can get this taken care of and move on to the next issue...

Thanks for the advice!

[Slumbo555]

I installed my rebuilt Midwest ABS module a couple days ago and so far do good! I haven't put very many miles on the car since the install (due to another car issue that was resolved today), but I feel pretty good about the fix. Thanks for the advice everyone.