MVS Volvo Forums member (now Contributor) ALF1 drops the Anti-Skid Fix knowhow for a fix that’ll save you about $300, or much more if you’re going to purchase a new yaw sensor.
Folks – The Active Yaw Control Sensor (found under the passenger seat and carpet) is a very expensive repair whether you purchase a new unit or send yours off to be re-manufactured by Xemodex or BBA Reman or try to get a used one.
Fortunately, I found that BCM (brake control module) codes indicating a failed Yaw Sensor may not necessarily indicate a $500+ repair is on the horizon. In my case, water had not penetrated the Yaw Sensor housing. Rather, water had pooled in the cowling of the plastic electrical fitting that passed through the Yaw Sensor housing. This fitting contains the connection pins to which the harness is attached. Removal inspection showed green corrosion deposits on and in-between the pins. I assume that this somehow shorted the pins and lead to the Yaw Sensor failure codes.
I was able to carefully dry and clean the pins and female wire connector, re-install (without the water…more on this later). Clearing and rereading the codes at my Independent shop revealed DTC ABS/BCM [ABS-0012 / Active Yaw Control Sensor, sensor not calibrated] or using VIDA the code becomes [BCM-0112 AYC-Sensors not calibrated]. For under $100, you can have a shop with VIDA recalibrate the Active Yaw Control Sensor…actually its called Reprogram Anti Skid Function. That’s the short version for those who have researched the blogs as I do. More detail follows for those who do not.
You can retrieve the Active Yaw Sensor from under the front passenger seat as follows:
– Electrically move the seat backwards.
– Turn off the car.
– Please check the blogs but I believe its best to disconnect the battery first.
– Pull the running board plastic cowling in the door frame…start by carefully pulling from the forward door frame then up from the running board…HEY THIS CAN BREAK if you are not careful.
– Remove the 4 bolts (15 mm, I think) that hold down the passenger seat and don’t lose them. Fold the passenger seat and lift it up and back…do not disconnect its electrical connection unless the battery is disconnected or you will throw an SRS code which will need to be cleared.
– Remove the clipped-on panel adjacent to the gear shift…gently now…relocate to a safe location
– Remove the carpet from under the seat…careful as you pull it away from other areas…take note of how it will go back in.
– Remove the water from under the carpet and dry it out. If there was so much water that it went to the back seat, remove more carpet and dry that too.
– Wet vac the carpet(s) as necessary
– Dry the foam under the carpet by hanging it up to drip, then use an old dry bath towel to compress and wick away most of the water, then hang it in the sunshine until dry.
– Remove the 3 bolts (10mm) holding the Infotainment amplifier (the black finned box under the seat)…do not unclip the electrical connections or it will trigger SRS codes that will need to be cleared.
– Now you can see the yaw sensor bracket…lower and towards the door
– TIME TO BE CAREFUL!…the Yaw Sensor is a motion sensitive device. Don’t drop the bracket or the sensor or treat them roughly. Slow mo’ here.
– Remove the two bolts (10mm) that hold the Yaw Sensor Bracket…one is accessible by ratchet the other by box end. The bracket has a tab on it that prevents it from being removed without also removing the lower seat slide guide (another 4 bolts). I simply used a screw driver and bent the tab downward just a bit so the bracket could be twisted and removed without the seat frame removal.
– Disconnect the electrical connection by squeezing the locking tabs
– Take the unit on the bracket to your work bench. Avoid static electricity…touch metal frequently
– Remove the unit from the bracket by removing the nut.
– After removing sensor from the car, I opened the housing by removing the 4 small torx metal screws and prying apart the housing with a flat screw driver. Although there was a lot of oxidation deposits on the outside of the housing, I found no evidence of water intrusion inside the housing. (Inside you will find a sealed metal sensor on a flat wire connected to a printed circuit board into which is plugged the pin connector that passes through the housing. All transitions through the housing have rubber gaskets.)
The printed circuit board inside has holes on each of 4 corners which are aligned and glued with spots of pale grey mastic of some sort to four housing posts plus one post in the center underneath. I was able to carefully pry the circuit board straight up and off the posts and mastic using a small flat blade screw driver (pry each corner of the printed circuit board a little bit and repeat…small steps)and inspect it.
As the circuit board comes out of the housing note that the electrical connector pins come out of the circuit board. Be careful here. (Do not disconnect the sealed metal sensor and connector.) For my unit there was absolutely no evidence of deposits or corrosion or water that I could see inside the housing. The outside of the housing was covered in oxidation powder. So, I carefully and thoroughly cleaned the housing gasket and housing edges using a tooth brush on the rubber and a brass brush on the cowling… don’t let particles get on the electronics!
Note that the connector containing the 6 pins comes off the housing and gasket. I did note green powdery corrosion on the external side of the connector down in the plastic cowling (is this the cause of the code?)and cleaned it carefully out using tiny screwdriver and Q-tips. Try to ensure there is no powder coating in between pins. I also carefully cleaned the female electrical fitting under the seat.
I reassembled the unit using small bits of plumber’s putty as a replacement for the mastic. (Plumbers putty is very dense but does not dry out and is intended for hot and moist local climates.)
Reverse the steps BUT BE SURE TO SET YOUR KEY TO POSITION II BEFORE CONNECTING THE BATTERY :
– assemble the Yaw Sensor,
– install it on the bracket,
– connect it electrically to the car
– install the amplifier,
– install the carpet,
– install the panel adjacent to the gear shift,
– install the seat,
– set key to position II
– reconnect the battery and
>>go find a Vida capable technician to read the codes.
With my unit the codes at my Independent Tech became ABS/BCM ABS-0112 / Active Yaw Sensor, Sensor not calibrated/. And at the Tech with Vidas BCM-0112 sensor, Sensors not calibrated.
>>Have the Vidas tech perform the Anti-Skid Reprogram to calibrate the Active Yaw Sensor. The codes cleared and Anti-Skid worked!!
Note that there was no way for water that got into the pin connector housing to drain (ever) because it is water tight and it faces straight up as installed…nice design Volvo!
Volvo XC90 – Anti-Skid Fix w/o Yaw Reman
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