I found a way to repair the common steering angle sensor or clockspring error which arises as a dash warning "Anti-skid temporarily off" or "Anti-skid temporarily disabled" and want to share it to hopefully help other avoid the $900 dealer charge.

Tools needed: VIDA/DICE, standard socket and screwdriver kit, compressed air, whiteout/silver pen, patience and decent hands

Note: actions in this repair if done incorrectly may damage your SAS! Follow at your own risk. Pictures are showing up in reverse order to my attachments, so references may be reversed in the text below.

Error codes fixed:

BCM-U042864 Invalid Data Received From Steering Angle Sensor Module - Algorithm Based Failures - Signal plausibility failure
SAS-C009404 Steering Angle Sensor Analog / Digital Sensor - System Internal Failures

Apparently this error is very common, and often requires a trip to the dealer who will replace your clockspring assembly which includes the airbag wire coil which looks like a clock spring (commutators not reliable enough) and the steering angle sensor assembly, which attaches to the clockspring with 3 screws. They are sold as a kit together because they must be rotationally aligned and limited by the number of turns they can handle without damage. The clocksping has a handy indicator built into it where you can see a yellow tab through a window when it's centered (and at/near its extremes).

The dash error of "Anti-skid temporarily off" would arise intermittently at first for my '08 XC90, and eventually stayed on. The anti-skid BCM computer utilizes the steering wheel position to assess expected travel between wheels and calculate unwanted slippage under acceleration and deceleration conditions, modulating the brakes as needed. If it doesn't receive a reliable steering angle sensor signal, it will disable itself for the drive.

In the garage, VIDA showed normal data for the SAS angle, direction, velocity, and BCM steering angle and yaw and lateral accelerometer signals at rest (first attached image). However, during a drive, VIDA showed that the steering angle signal from the SAS and BCM locked up, froze at large left turn steering positions (over 300 degrees, attached image 2). This signaled that the SAS controller was receiving uninterpretable signals from the SAS at large left wheel positions, and it was giving up, throwing the error.

I had read that the SAS units utilize optical encoders, and suspected that when they 'go bad' it's really just some dust in the optical path, but couldn't yet see how that would occur only with large steering wheel rotations, so commence disassembly.

1) There are videos on youtube which describe in detail how to take out your clocksping, so I'll skip that here. It's not a hard job. Make sure you mark your steering wheel position relative to the splined post after removing the 18mm bolt and before removing the wheel.

2) Ensure that the clockspring is centered, and unscrew the 3 screws holding it on the steering column. From now on your job is to mark and remember the orientation of how these pieces go together. Flip it over and mark with whiteout the rotational position relative to the housing (3rd image, 2 screws already removed from center).
Vacuum the dust and dirt from all around it.

3) Unscrew the 3 screws holding the SAS to the clockspring on the back, and after removing the SAS, immediately mark on the back of the clockspring its rotational position (4th attached image). Set the clockspring assembly aside.

4) Set the marked SAS on a table and remove the 3 inner screws which hold the front and back coupling rings in place. MAINTAIN the position of the back coupling ring! Carefully lift the front coupling ring off and mark with whiteout the relative position of the back coupling ring to the inner encoder wheel (attached image 5). The back coupling ring has 3 posts which protrude through alignment holes in the encoder wheel.

!! If you allow the back coupling ring to fall off, the encoder wheel will become loose in the enclosure. In this state, if it is lifted and rotated it can skip teeth and loose its position relative to a linear encoder which is coupled with a gear. This can be bad news and prolong your repair as you try to find the correct position again.

5) With the front coupling ring off, you can now carefully pop up the clips holding the cover on, exposing the encoder electronics underneath. Be clean! this is static and dust sensitive instrumentation! (attached image 6)

The design of the encoder is now clear. There is a rotary optical encoder portion with diodes and sensors attached to the PCB (white silkscreened solder joints), and a linear 'raster' optical encoder portion which is the part that protrudes. The rotary encoder can probably encode 360 degrees of travel with a 1.5 degree resolution, and the coupled linear encoder then encodes which rotation position the assembly is in with a wider rotational range but lower resolution. It should be approximately in the center of travel. The rotary and linear encoder results need to be roughly in agreement, or the plausibility error will be thrown.

6) You can now get your compressed air can and blow out the area of the optical rotary encoder and down the slit of the linear encoder. I suspect that my error was due to dust blocking a beam in the linear encoder area, resulting in incorrect data readout.

7) You can now re-assemble the entire assembly, clear codes, and test.



Note: in my case, I purposefully rotated the rotary encoder wheel about a half turn while keeping it disengaged from the linear encoder drive gear. When I went to test in the car, immediately invalid data error was thrown and the VIDA SAS angle readout was locked at 0. This was corrected via a few trial and error gear relative adjustment attempts, keeping the wheel and airbag off to speed the process which of course threw more codes to be cleared on final assembly. It's possible this relative adjustment process also helped eliminate the error code, if for some reason the linear encoder had become slightly misaligned through use. It turns out there is a specific tool being sold which help savvy techs ensure the SAS is properly aligned!:

https://www.ebay.com/itm/153949744645?ul_noapp=true

This would no doubt save a significant number of unnecessary clockspring assembly replacements. I am not associated with the seller.



After this cleaning repair, codes no longer arise through turning the steering wheel lock to lock (attached photo 7).

I hope this helps some, and at least highlights ways that VIDA can help to identify which component is at fault via live-drive data plotting of SAS angle, yaw and acceleration sensor read-outs.

Calibration of the BCM with a new clockspring or SAS or yaw sensor can be performed with VIDA after this work by opening BCM telemetry, click the advanced tab, open BCM calibration, and then click the image of the controller box per instructions.


Image 1: plausability error angle readout freeze at large left turns


Image 2: SAS and BCM parked garage read-outs


Image 3: Back of clockspring assembly with white mark on Steering Angle Sensor (SAS) front coupling ring a bottom.


Image 4: inner reference mark on back of clockspring assembly after removing SAS


Image 5: Front coupling ring removed from SAS, inner alignment marked


Image 6: Inside SAS showing electronic circuit board. Linear encoder at the bottom, linear encoder drive gear at bottom right, inside


Image 7: Full steering sweep, no errors or freeze

 

Hi. Thanks for the write-up.... I tried it and it worked for me..... though today, I had to turn far left, and it came on again... Maybe i didn't clean the diode well, as I didn't take out the diode, just blew in air.

 

UPDATE.... This method works!!!! Kudos to DRLAVA ! Its refreshing to know that some people here in the US still have original thinking, and he was right.... Code is now gone even when I turn hard in either direction.....no more dead spots...

So the first time I tried the clean, i broke down the SAS to the point where the green circuit board screws were removed, and i had only blown in compressed air into the holes of the diode assembly. And the result was the anti Skid message had went away partially that is until I turned sharp left, So a partial success.

Then my second attempt at cleaning, but this time I disassembled the entire SAS...and I think the key to it all was this razor thin metal piece with a 60° hair-thin slit, which had oh so few dust particles I could actually see caught in the slit, when held to a very bright light. I manually cleaned it with soap and water, and slightly bent it to better conform to the slot it sat in. I fully agree with DrLava, and dust (on this razor metal slit) is the holy grail and is the culprit to beloved anti skid issue when your vida error message says it's the SAS. I also cleaned the raster gear and the discs with soap and water, as I could not fully figure out how the light diode works and it looked like there were reflective type marks on one disc, so I cleaned them. Though like an idiot I had washed off all the alignment markings one needs to make for reassembly. So much for the red sharpie permanent markers being permanent. So I got VERY lucky reassembling and it works.

So, you need to disassemble the entire SAS, taking out the raster gear with the razor metal slit, and wash with soap, hold to bright light to make sure there isn't a block all the way through the slit... blow out the hole that the metal slit goes into. Retighten everything.

A few caveats. I had used too much loctite red on the steering wheel bolt and it dropped into the groves and couldn't get the wheel off. And when I finally did I pulled the clockspring ribbon out of its holder, and got lucky putting it back in. Only a drop is needed. Also I spent a half hour trying to pop the airbag out. It should be easy but for me it wasn't, sticking the screwdriver in back, finding the spring, and lifting up. I had also forgot to mark the column and the red loctite obfuscated the markings so it took me another attempt to align wheel.

Anyway, this works !!!!

 

I have an '06 XC90 2.5 I5 turbo and have the "ANTI-SKID TEMPORARILY OFF" warning, the yellow triangle lit up and "ABS" in the display on the right side status panel. Question #1 - Is this, for sure, a steering angle sensor issue and question #2 - Does the live data testing require a specific subscription in the VIDA program? I have the VIDA DIce 2014 tester and no subscriptions.
Thanks in advance for the help!

 

1. Gotta get it scanned and the code will tell you if it's the SAS. If it is it's only a matter of cleaning the dust out of the slit, and bending the metal the slit is in, because over time this bent piece will naturally try to straighten out, which will affect the laser, and thus a false reading. out.

2. I don't have VIDA or DICE and didn't need them to fix my SAS. For what it's worth, my code hasn't come back since I cleaned mine. Follow instructions in this thread.

 

Tried a scan using my old OBDII tool and got no codes even with the ABS fault. Hooked up my DICE unit and got the following DTC's pictured;


Also, my warning changed to ABS/Anti-Skid service required from ABS Temporarily Off. Hope this info helps. Thanks again!

 

Many years ago my Anti-Skid warning light came on, yet there was no error code... someone told me the ABS sensors in the wheels get blocked, and to go in reverse fast then slam on brakes, a few times, to loosen it up.... it had worked for maybe four years....that is, until the SAS was causing the problem.

 

I'll try ANY possible free remedy before I go tearing apart the clock spring. If it can be broken, I'm the man for the job!

 

Take it to AutoZone or advance Auto for a free reading, maybe your OBD scanner isn't reading. The old ones can be finicky. If you don't have a P code it won't be the SAS.

 

Took it to the zone today and their scanner showed no codes even with the ABS/Anti-Skid Service Required warnings.

 

hi all,

today i followed this great tutorial on my 05 XC90 V8.
the original DTCs are gone, now i have these:
BCM-C111768 Stability function. Algorithm error. Event-controlled information, B8444S
BCM-C110687 Communication between control modules. Bus/message error. Message missing, B8444S
BCM-C110668 Communication between control modules. Algorithm error. Event-controlled information, B8444S

VIDA states: the BCM-C111768 is an consequential error of the other two.
And: if the BCM-C110687 an BCM-C110668 pop up together, have a look at the SAS for DTCs.
but there is no DTCs from SAS.

Any ideas? Thanks you!

 

I was wonder where the location of the slit your are talking about. I just had is apart, blew air in the lower part of the SAS , reassembled and still have warning on. Pic or diagram would be great. Thanks

 

[firstly a big thank you to @drlava for the original post.

I was banging my head against the wall trying to get an aftermarket decoder ring to work.

I went back to the original and dismantled the original parts, gave it all a clean and put it back together.

I had to disassemble it due to the angle being off, but using Vida I was able to get it aligned, then reassembled everything and reset the codes and all was good.


QUOTE=XCCANADA;511923]I was wonder where the location of the slit your are talking about. I just had is apart, blew air in the lower part of the SAS , reassembled and still have warning on. Pic or diagram would be great. Thanks[/QUOTE]


@XCCANADA when you dismantle the SWM, the inner ring. There are two screws which release the tall bit of the module that has two metal spindles. When you lift off the cap, there is a angled metal rectangle that is about 20mm x 10mm. The slit is in the piece of metal.

The warning message on the dash won't go away until you reset the codes using Vida or a diag tool that lets you clear error codes for the abs system.

 

This error was making no sense at all. Now it does!

Thank you for this great work with excellent words.

 

I just dove into this myself before finding this post (had to google the ALPS part number on the board). You can re-clock this fairly easily without marking it (or if you wipe off your mark ). I'll assume it's nearly fully broken down in my explanation.

Start with contact reel turned full clockwise. Turn Counter-clockwise ~3 turns until yellow roller is inside the window at ~8 oclock, with the "nub" at ~1 oclock (screw from the holder in the wheel should fit into slot).

With sensor dissembled, you should have 3 circular plastic pieces. One goes between sensor and contact reel. On one side of this piece, there are 2 nubs with different sizes. There are two differently sized holes on the contact reel. Match these up, leaving piece on the reel. The same piece should now be showing 2 similarly sized nubs. THE REVELATION: One of these nubs has a tiny triangle on the tip. Take note.

Screw Sensor back onto Reel without replacing the cover

Now look at the assembly with the slotted plate & springs. Once clean, put this back as you found it. With the larger circular gear out of the way, turn the little gear. There are 4 lines: one on the part that moves up and down, and 3 on the other side. Line up the single line to the middle line.

Now carefully inspect the larger gear wheel. There are many holes. One has a tiny triangle next to it. Carefully slot the triangle nub into this hole, while keeping the small gear in calibration.

Now, screw the circuit back on. Check the variable resistor while you're at it (looks like a screw). Some russian website says 160 ohms works, tweak to match.

Re-cover the sensor. The last circular piece will also have a triangle, which will match with another triangle around the cover.

I'll add pictures to illustrate if I ever feel like doing this process again lmao