Faulty Speed Sensor or faulty ABS Module?

2001VolvoXC70 · Post by **2001VolvoXC70** » 29 May 2010, 15:59

Can a faulty Speed Sensor trigger ABS & Traction light?

I have the abs light on, and also the traction light comes on at about 15mph. My abs is not working. I pulled codes p0722(output shift speed sensor) and p1618(fault in lead between aw50 and motronic 4.3.

I have located the speed sensor on my transmission. Is there a way I can test it? Also, I am wondering if a bad speed sensor can make the abs light come on and the abs not to work. Or could it be a faulty module triggering the speed sensor fault. I don't want to buy a new speed sensor if I don't need one, and I have already opened the abs module to find all my solder in perfect shape.

Post by **JRL** » 29 May 2010, 17:53

It always says that, it's not!
99-44/100% it's the ABS module
Rebuild for $100
www.modulemaster.com

kejeon · Post by **kejeon** » 29 May 2010, 23:52

did you do anything to cv axles? I have the ABS triggered and Traction light on due to the replacement axle I got do not have a gear-like thing, so the sensor won't read the axle speed.

2001VolvoXC70 · Post by **2001VolvoXC70** » 31 May 2010, 01:41

Haven't done anything to the cv axles. Im going to remove the abs module and see what codes get pulled then. If Im still getting the p0722 Im thinking it cant be the abs module and the sensor must truly be faulty.

jda2000 · Post by **jda2000** » 31 May 2010, 13:04

fix your ABS module, and I'll bet your tranny issue will resolve itself.

The TCM gets data from the ABS module, and if this has failed the tranny will give a failure message.

2001VolvoXC70 · Post by **2001VolvoXC70** » 01 Jun 2010, 16:02

Planning on sending it to bba in Canada. The only thing is I have opened the module and none of the soldering was cracked. I have re-soldered terminals as recommended but still no change. If I send it out are they going to find electrical components that have failed? I thought the issue was with cracked terminals not failing electrical components.

That is why I'm wondering if I should have volvo diagnose first. Or could it be that this p0722 code I'm pulling is actually a faulty transmission output speed sensor, which is causing the abs not to work. Will the module trigger the ABS light and and service transmission message if this sensor is failing? Will the abs module stop working if this output speed sensor isn't sending a signal to the abs? This is my dilemma...I don't know exactly the communication. I don't want to be throwing money out the window ordering sensors and having modules repaired that don't need to, but I got to start somewhere.

I'm thinking first to measure the resistance at the transmission output speed sensor to see if it is above 10M ohms, or measure it against the input speed sensor. The resistance should be similar. Secondly, reconfirm that all my wheel sensors are working properly, by checking the impedance at the ABS module and also rotating my tires to make sure they are registering resistance properly. Thirdly, I think there is a ABS relay somewhere, which I haven't found yet or tested but I will follow the electrical to make sure I'm getting power at the appropriate spots. If all the previous check out good than off to bba I am with a module rebuild. Hopefully they won't mind that I have already tinkled around with it.

2001VolvoXC70 · Post by **2001VolvoXC70** » 03 Jun 2010, 01:41

I have checked the resistance at the transmission sensor and also of the abs wheel sensors at the module and all seem to be measuring resistance properly. Crossing my fingers while my module is off to bba with a rebuild.

royboy · Post by **royboy** » 07 Jun 2010, 20:40

2001VolvoXC70 wrote:Haven't done anything to the cv axles. Im going to remove the abs module and see what codes get pulled then. If Im still getting the p0722 Im thinking it cant be the abs module and the sensor must truly be faulty.

100% abs mod

TerryMcMahon · Post by **TerryMcMahon** » 10 Jun 2010, 21:11

I had the same problem. ABS module was fix by a local non-volvo guy and worked like a charm. No more speedo problems nor ABS and Brake failure lights as well. Good Luck

2001VolvoXC70 · Post by **2001VolvoXC70** » 28 Jul 2010, 04:39

Sent the module into BBA they hooked it up to there tester and found nothing wrong with it. Went back to volvo and asked to look at the diagnose sheet and sure enough a rear sensor is registered as faulty. Bought a new sensor...now I just need to figure out how to get it into the car from the wheel????