Hello everyone!
I'm almost at my wits' end with this one, so hopefully someone can shed some light! I have a 2012 Unlimited Sahara with the 3.6L and Nag 1 auto transmission. I have had a myriad of wiring issues with this one. Recently, I am having an issue where the trans will go to limp mode and stays in second gear, but does not throw any codes. I do not feel like its a mechanical issue, but an electronic or electrical issue. I have been inside the transmission through the valve body and the pan was really clean super minimal deposits on pan magnet. I replaced the conductor plate while I was in there. I have a bidirectional scanner that allows live data monitoring and module resetting. Here are some things I have noticed during my diagnosis:
I'm almost at my wits' end with this one, so hopefully someone can shed some light! I have a 2012 Unlimited Sahara with the 3.6L and Nag 1 auto transmission. I have had a myriad of wiring issues with this one. Recently, I am having an issue where the trans will go to limp mode and stays in second gear, but does not throw any codes. I do not feel like its a mechanical issue, but an electronic or electrical issue. I have been inside the transmission through the valve body and the pan was really clean super minimal deposits on pan magnet. I replaced the conductor plate while I was in there. I have a bidirectional scanner that allows live data monitoring and module resetting. Here are some things I have noticed during my diagnosis:
- While monitoring the TCM module, the output shaft speed is reading at the top of the range WITH THE ENGINE OFF! This reading is a calculation of both rear wheel speed sensors (all 4 if 4WD is engaged) and the n3 out put speed sensor from the conductor plate. The n3 sensor and all wheel speed sensors are reading correctly.
- The gear shift indication does not allow manual shift selection.
- It will throw a P0731 - Gear Ratio Error in 1st code. I feel this is a symptom code not a cause after the trans stays in second gear and it comes in after a stop and start (it's taking off in 2nd gear....of course the ratio is off)
- I have gotten lost communication codes across modules connected to the Canbus C circuit, but those went away.
- I did some continuity tests on the canbus circuit (plan do do more)
- I took it to a professional shop for diagnosis; they said it was an issue inside the transmission. I replaced the conductor plate with a better one. Did not help
- I also may have an ABS module issue, but again, the wheel speed sensors are working properly. I actually purchased a rebuilt one (took a chance) but couldn't write the vin to it. Took it to dealer they said it was DOA. They also said they updated the programming on a couple of modules. I'm beginning to think they may have corrupted something, but they will never admit that.