Anti-Skid Temporarily Off - $0 SAS DIY Technical Repair


drlava

Recommended Posts

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.

 

 

 

 

 

 

 

 

 

no sas error.png

IMG_9365.jpg

IMG_9364.jpg

IMG_9363.jpg

IMG_9362.jpg

IMG_9356.jpg

steering wheel sensor left lockup.png

Link to post
Share on other sites

This is awesome - thank you for sharing. I have the anti skid message on our 14 xc90. It comes and goes... I think a full lock left turn is where it trips on ours.

Link to post
Share on other sites
  • 2 months later...
  • My 2005 V70 often does this when parked with the wheels on full lock. Then goes into "Anti skid temporally off". Then it resets after 20 yards, and all is fine. I just live with it, like all the other problems it has. :rolleyes:
Link to post
Share on other sites

Archived

This topic is now archived and is closed to further replies.

  • Similar Content

    • By whosaidwagonsarejustforfamily
      Hi i was wondering if someone could please help. I will start with the history, 1 1/2 years ago my Anti-skid message would come on and off sporadically.
      I checked for codes: bcm-u041464 (invalid data received from 4wheel drive clutch control module) along with other codes dem-p188914 (oil pressure pump performance).I first replaced the Aoc pump with fluid and filter. Message came on and off again.
      I than removed the Dem and had it repaired. They sent it back no problem found.
      I booked it in to Volvo dealership. Was recommended to try the haledex temp sensor
      replaced the sensor same issue! (ANTI-SKID MESSAGE). The dealer said it may also pump again overworking.
       
      Anyone with thoughts?
       
      Thanks
       
       
      ****************UPDATE************************
       
      So I sent my BCM in to a module repair centre and they said it was faulty and cannot be repaired. I ordered a new module and installed it and had it programed to my car. But I am still getting codes bcm-u041464 and dem-p188914. Anyone have any more suggestions? I do have access to a VIDA, is there any other things to check?
       
      Thank you for your time.
       
       
       
       
       
    • By Stefan Mohammed
      Hey guys,

      The clockspring for my 2000 S80 2.9 RHD is torn. I can't locate a part number on it and the only identifying lablel is a barcode with the text *1TH0507*A on it. I searched up on VIDA and I found several part numbers for my clockspring. I'm not sure which part number I need.

      The connector into the SWM is a 4 pin connector located on the top right of the clockspring and the connectors on the steering wheel side are: (1) 2-Wire Airbag Connector (orange cable sleeve, wire colours blue and brown), (1) 2-wire Horn Connector (grey jack, wire colours green and white) and, (1) 3-Wire Steering Wheel Control Connector (Green Connecor with 10 holes, 3 wires, wire colours blue, red, black). The Steering Wheel and Horn connector cables are sleeved together in a black sleeve. The steering wheel controls that came on the car were for cruise control and for audio control. The car came with a HU601 Headunit (no RTI) and standard cruise control (STC only).


      Steering Wheel Side of Spring (Note wire colours)


      Green connector is for steering wheel controls and grey is for the horn


      Steering wheel connector (grey) and horn connector (grey). Pinouts are: (STEERING WHEEL CONTROLS: 1-Blue, 2-Red, 3-Black, 4-EMPTY, 5-EMPTY) (HORN: 1-White, 2-GREEN).


      Single airbag connector (2 wires in orange sleeve)


      Alternate view of single airbag connector (2-wires in orange sleeve)


      Barcode on the side of the clockspring


      SWM connector on clockspring (the internal spring/pins are removed in this picture but it's a 4 pin connector). If you are looking head on to the clockspring (the side with the warning label on it) then this connector is at the top-right of the steering wheel.

      Thanks a mil - Stefan.


      [EDIT] VIN Number: YV1TS94C5Y1069110

    • By eastcoastbricks
      I have a 1998 V70 AWD, which I have swapped for 15g, whites and a T5 ECU. Car runs great aside from the enevidable SAS, and EVAP codes. P0410 and so on. I have removed the T5 ECU for the time being. My question is since I do not have SAS, can I perform the SAS delete witht the diode in the ecu, or will the ecu still look for the compents that were never on the AWD vs. the T5 such as the air pump, solenoid and relay. I know the best solution is to have my LPT ECU tuned but It is expensive to have these shipped out of country and back. Any Ideas or anyone who has concored these issues before would be awsome.