Subaru Diagnostic Woes, Parts is Parts
In our work we get those challenges that test our confidence. This project is one of those times. The vehicle was at a repossession lot getting ready for sale. The traction light was constantly on. When scanned both the trouble codes and the vehicle data pointed to the steering angle sensor. Subaru decided to make this sensor real special. It must be because the street price is darn near $400. In checking with the local dealer, it was not a stocked part. This always raises red flags.
Continuing on with the diagnosis all the basics were covered. Power, Ground, Hi and Lo CAN signals. Everything checked out up to the connector for the steering angle sensor. No other codes were stored leading to another problem. I went to a local wrecking yard and purchased a steering column. I extracted the SAS and installed it. The result was the same. Digging deeper into the service information, I went through the trouble tree. Yep, it got me into trouble.
Following the flow chart based on the codes the result was to replace the VSC control module. I went to the wrecking yard and got a used one. I was just not convinced that it would fix it. Here I will give a warning on installing a used ABS/VSC in a Subaru. Make sure in the scan data that the codes match between the one being replaced and the donor. Even the factory tool will not rewrite the coding. I have tried a few times. I have yet to change this once written. Fortunately, the codes were compatible between the two modules. Still, no joy. Now I am getting frustrated. I go to Google, Youtube and the forums. One guy stated that the YAW sensor will keep the SAS from calibrating. I found one locally for around $15.
Instead of going back and forth to the lot, I set up the system on my bench. ABS/VSC controller, Steering Angle Sensor and YAW sensor. In order to see what modules were communicating, I hooked up a CAN tracer and monitored the different modules. The steering angle sensor reported as node 2. I could see that it was communicating. The numbers did not change on the scan tool screen. Back to square 1. Where to go from here.
The original problem was that the vehicle system did not recognize a change in signal from the steering angle sensor. Could the wrecking yard part be bad? I ordered another column. I extracted the SAS and connected it on the bench. WOW, the numbers are changing! Next day, SAS installed and Traction Control Light is off. When extracting the second SAS I noticed that more screws were found in the module than the one I took out before. I suspect that someone purchased the column, switched the part and took it back for credit.
In conclusion, even though the SAS was communicating across the CAN lines, the values were not changing. The sensor appears to have a hall effect array that reads the cutouts in the wheel. Maybe that part goes bad. Another point worth mentioning. The diagnostic line that the scan tool reads is not the CAN lines. It is the K-Line. In order for the scan tool to see the ABS/VSC that K-Line needs to be connected. Otherwise you get a no communication error. Somehow we believe that we can't get a bad part new or used. I am seeing this more and more. Product bad right out of the box.
Dang Chris....another scope-meter! Do people just hand you new tools to test? If not, I think "shopaholics" has meetings like AA. :-) The important lesson here is that your original instincts and testing were valid. Tough crap to the owner if the part is expensive. Great tip about the K-Line too!!
Geoff, Without getting into too many details, I do testing for different companies on either new products or ones they want to introduce. As for the tracing tool, I used a Vector CANCardXLe tool I purchased on eBay and a tracing program I found on the internet. For scanning, I used SSMIII. On this job I ate all the bad apples. Since the parts were used I still came out OK. On things like this…
Chris, in regards to the statements, "As for the tracing tool, I used a Vector CANCardXLe tool I purchased on eBay and a tracing program I found on the internet"; Maybe you could do a post on just that alone? I have no clue what you are talking about right there. I know you are referring to the screen shot with all numbers and codes, which I glanced past, as it was all French to me. :-) Thank…
also I apologize that I keep reversing your name in my brain. Mike Chris Chris Mike. Sorry!
Awesome Post.....Michael, after reading post after post, I can say I would love to shadow you for a week or 2. Your case studies along with a few specific others here and the problems that you encounter are on another level compared to what I see day to day in the shop....I particularly am intrigued by yours and other's testing methods on this site....awesome read and thank you for posting!!!!
Same out here Samuel. Even though I am the "diag guy" at the shop here, RO's with "check noise" and "check leaks" outnumber the quality DTC investigations 10:1. Legit diagnostics is practically my hobby. I read, and watch, far more than I actually ever do.