CVT failure need help diagnosing further

[brianjwilson]

Hello! First post of what I'm guessing will me many over the years with my new to me 2013 Crosstrek with 187k miles. I was driving it this week and after 10 minutes, when starting from a stop at a light in drive, my CVT made a quick and loud grind noise and immediately after would not engage in either drive or reverse. All the dashboard lights came on as well. Had it towed home to diagnose. I bought it a few months ago and I know it had the valve body replaced by the prior owner just before I bought it, but that's what I suspected anyway given my reading on all the forums. A second symptom is when shifting from Park or Neutral into Drive or Reverse, you can hear the engine make a very slight temporary change in RPM and then a faint spinning sound coming from the transmission area. No spinning sound when in Park or Neutral.

I started with a basic code scan and got P0700 (generic transmission code). I use FreeSSM but the cable I'm using will only connect to the ECU and not the TCU, so I couldn't pull the more specific codes. So I went ahead and started diagnosing the valve body. I couldn't get a great ground and consistent reads using the transmission case as a ground (which the solenoids are grounded to), so went ahead and pulled the valve body from the transmission and read all the solenoid resistance values directly from the plug on the top of the valve body. All values checked out fine. So put it all back together and no change.

Two other things I've tried - verified that the brake lights work properly (to rule out BLS), and disconnected the battery to clear any settings that may be affecting it. And I've verified that the CVT fluid is properly filled (I did a drain and fill twice a couple of months ago).

Last thing is that for a couple of weeks before this happened, there would be a slight hesitation and slipping when changing from reverse to drive when first driving and engine / transmission was cold.

Any ideas? I'm still working on getting my VAGCOM cable working for the TCU. But I'm trying to find other things I can try at home without throwing parts at it and before having it towed to a transmission repair shop, where the cost will increase exponentially.

Thanks for your help!

 

[Ecmbuster]

The model and associated schematics will help. Model and Engine needs to match as in the image.

FreeSSM operates on the "K" line and not on the CAN (Controller Area Network) protocol.
The VAGCOM cable is dependent on the chipset.
This attachment is how I succeeded over many years of using the SSM2 protocol with older Subaru models.
The image is the 5EAT transmission connected with FreeSSM

The transmission is an animal to get out and requires extra equipment, A used transmission can be installed or have it / vehicle sent to a transmission shop. Another avenue is a reconditioned unit but again, it take specialized equipment to remove and reinstall the transmission.

A generic code reader is not what you need. Modern tools such as Snap-On, MAC, Launch or Autel will read the protocol with a great degree of accuracy.
Another version I also use is Easy Diag and can interrogate the entire network.

 

[brianjwilson]

The model and associated schematics will help. Model and Engine needs to match as in the image.

FreeSSM operates on the "K" line and not on the CAN (Controller Area Network) protocol.
The VAGCOM cable is dependent on the chipset.
This attachment is how I succeeded over many years of using the SSM2 protocol with older Subaru models.
The image is the 5EAT transmission connected with FreeSSM

The transmission is an animal to get out and requires extra equipment, A used transmission can be installed or have it / vehicle sent to a transmission shop. Another avenue is a reconditioned unit but again, it take specialized equipment to remove and reinstall the transmission.

A generic code reader is not what you need. Modern tools such as Snap-On, MAC, Launch or Autel will read the protocol with a great degree of accuracy.
Another version I also use is Easy Diag and can interrogate the entire network.

Thank you for that info on the cables - I have a new one with FTDI chipset on the way and hopefully that will help me get connected with FreeSSM to the TCM. In the meantime, I bought a different reader (BlueDrive) that I could get same day and gave me a lot more codes than my basic reader, a wide variety of codes that appear to be 1) TCM communication related, or 2) valve body related...
- Potentially TCM or wiring related: U0101 (lost comm with TCM), C1422 (VDC interruption), C1431 (AT abnormal), C1531/1532 (BLS off/on faults), U0164 (lost comm with HVAC control module), B14A1 (sunload sensor circuit low / open)
- Potentially valve body related: P2746/2750 (intermediate shaft speed sensor B/C circuit / range performance), P0974/0977 (shift solenoid A/B control circuit high)

So to see all those communication or other module errors (which I believe the TCM is part of the chain of modules that all have to talk together nicely) leads me to believe it's the TCU or a wiring / harness issue. I've already checked the continuity / resistance between the valve body connector, the transmission connector harness, and the transmission to TCU harness and didn't find anything wrong. Will poke around more. I've also checked all the solenoids on the valve body and all resistance readings were within range when cold.

I found an updated diagnosis tree for the control circuits high / low and for high readings it says to heat up the transmission to 80C and then check the resitance again. If it goes really high reading or to an open circuit, then that would point to the valve body needing replacement. But if it doesn't, that would point to the wiring or TCU.

The thing that still makes me think it's the valve body is just common sense and the odds (that's what usually goes bad), and the fact that the car will not shift out of Park. The shift lever isn't stuck - I can move it to Drive and Reverse - it's that the transmission doesn't engage. That points to a mechanical issue to me, like something wrong with the valve body.

 

[Ecmbuster]

You still need to identify the correct model. I believe those models have similarities but models do have some differences. Look at the earlier image to match your model.
U = Network, C = Chassis, B = Body, P = Powertrain
Check all the ground connections from battery negative, to the body and engine. Check all the ground straps from the engine to the body.
FreeSSM is only the "K" line and does not access the CAN Network. All you get is Engine and Transmission
A quality multi-meter will help but a Factory Service Manual is a great advantage.
If you have access to the TCM or ECM, post images. A decent laptop will create screen images using ShareX.
https://getsharex.com/
My setup is in the next image.
It can take one defective CAN controller to take down a network or parts of a network..
Non OEM additions need to be disconnected for any network tests.