C121C code after sitting for a year - 3.6JK
04-14-2023, 10:16 AM
#1
JK Newbie
Thread Starter
C121C code after sitting for a year - 3.6JK
TL/DR: My JK sat for a year, the rear wheel was frozen in place and broke free- but now i have the Traction Control Assist light on and its throwing a C121C code - not sure if this is common but wanted to ask here for any advice as to what to check first and if that frozen wheel is a good place to start digging given what happened.
Full Story:
So my 2018 JK, with the Pentastar 3.6L engine, and ended up needed to have the noisy lifter/rocker replaced, and when we got in there we noticed how much sludge had built up and knew it needed some major work. I had just been laid off, so i decided to take the time to actually learn how to work on cars, got the FSM and a subscribtion to AllData for the wiring diagrams, and thought myself along the way (with a ton of help from guys on here!), so I pulled the motor, got in on the bench and broke it down into every possible piece i bagged and tagged, sent the head and block out to a machine shop to have to faced and measured, and got it all back together finally!! Since i had it open, i got all new main crank bearings and had it and the cam shafts polished (i did plastiguage them when replacing bearings), piston rings and bearings replaced, new oil pump, new water pump, new timing chain/gears/guides/tensioners/etc, Pretty much anything that came into contact with that dirty oil except the large parts i had the shop machine power wash, then verify they were all still within acceptable tollerances according to the FSM. This took about 8 months between family issues that came up, the garage was 40 mins away from home so it was a long haul to even work on it, and long story short it took for ever.
We finally got it running, and the first time i put it in gear the car did not want to move. I gave it more and more gas until i got to about 2.5k RMP when it finally made a loud POP noise. My brother was watching the driver side and said he saw the wheels moving, but when he moved to the passenger side he saw the rear passenger wheel was frozen and sliding - the pop noise is when it broke free and started to roll again.
Im about 75 miles into the break in process, already done 2 oil changes since the initial start to wash out all the assembly lube and shit that forms when the engine breaks in, but im stumped on this C121C error. The diagnostics show the C121C error as "Torque Request Signal Denied" but didn't give me any specific details about what wheel or where its coming from. There was also two other codes a C2100 "Battery Voltage Low" and C2102 "System Voltage Low" but the car was sitting for almost a year so im not shocked if we killed the battery over that time.
Keep in mind, im a total noob here and only worked on my dirt bikes so this is a large undertaking for me - so im totally open to any suggestions even if they think its stupid or common sense lol. Im amazed i got the engine rebuilt and running, but now i just gotta sort out these last few issues and ill be good to go! Funny note, after working on this thing for 8 months and putting it together, taking it part (broken screw), putting it back together, trouble shooting electrical issues (false error caused by aforementioned broken screw) that i feel like i know this 2018 JK so well now that i could work on a Pentastar 3.6 engine with my eyes closed now lol..... ok ok ok - so i know enough to be dangerous under the hood but now that its getting to wheel sensors and ABS stuff, its back to the learning board for me.
Thanks guys!
Any help would be greatly appreciated!!
Full Story:
So my 2018 JK, with the Pentastar 3.6L engine, and ended up needed to have the noisy lifter/rocker replaced, and when we got in there we noticed how much sludge had built up and knew it needed some major work. I had just been laid off, so i decided to take the time to actually learn how to work on cars, got the FSM and a subscribtion to AllData for the wiring diagrams, and thought myself along the way (with a ton of help from guys on here!), so I pulled the motor, got in on the bench and broke it down into every possible piece i bagged and tagged, sent the head and block out to a machine shop to have to faced and measured, and got it all back together finally!! Since i had it open, i got all new main crank bearings and had it and the cam shafts polished (i did plastiguage them when replacing bearings), piston rings and bearings replaced, new oil pump, new water pump, new timing chain/gears/guides/tensioners/etc, Pretty much anything that came into contact with that dirty oil except the large parts i had the shop machine power wash, then verify they were all still within acceptable tollerances according to the FSM. This took about 8 months between family issues that came up, the garage was 40 mins away from home so it was a long haul to even work on it, and long story short it took for ever.
We finally got it running, and the first time i put it in gear the car did not want to move. I gave it more and more gas until i got to about 2.5k RMP when it finally made a loud POP noise. My brother was watching the driver side and said he saw the wheels moving, but when he moved to the passenger side he saw the rear passenger wheel was frozen and sliding - the pop noise is when it broke free and started to roll again.
Im about 75 miles into the break in process, already done 2 oil changes since the initial start to wash out all the assembly lube and shit that forms when the engine breaks in, but im stumped on this C121C error. The diagnostics show the C121C error as "Torque Request Signal Denied" but didn't give me any specific details about what wheel or where its coming from. There was also two other codes a C2100 "Battery Voltage Low" and C2102 "System Voltage Low" but the car was sitting for almost a year so im not shocked if we killed the battery over that time.
Keep in mind, im a total noob here and only worked on my dirt bikes so this is a large undertaking for me - so im totally open to any suggestions even if they think its stupid or common sense lol. Im amazed i got the engine rebuilt and running, but now i just gotta sort out these last few issues and ill be good to go! Funny note, after working on this thing for 8 months and putting it together, taking it part (broken screw), putting it back together, trouble shooting electrical issues (false error caused by aforementioned broken screw) that i feel like i know this 2018 JK so well now that i could work on a Pentastar 3.6 engine with my eyes closed now lol..... ok ok ok - so i know enough to be dangerous under the hood but now that its getting to wheel sensors and ABS stuff, its back to the learning board for me.
Thanks guys!
Any help would be greatly appreciated!!
04-14-2023, 11:36 AM
#2
JK Jedi
I was just in your other thread as well, and as I noted there, I've been dealing with a P0369 camshaft code myself. What I would say is that when I throw this code, it is often followed by this same ABS/traction code. I really think this could just be related to the CPS issue your having and that you might just focus on resolving that before worrying too much about the C121C. Just my opinion based on myself getting that code related to the CPS code, and myself having zero ABS issues outside of that CPS code.
10-05-2023, 11:08 AM
#3
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Join Date: Oct 2023
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I was just in your other thread as well, and as I noted there, I've been dealing with a P0369 camshaft code myself. What I would say is that when I throw this code, it is often followed by this same ABS/traction code. I really think this could just be related to the CPS issue you are having and that you might just focus on resolving that before worrying too much about the C121C. Just my opinion based on myself getting that code related to the CPS code, and myself having zero ABS issues outside of that CPS code.
How did you end up fixing this issue? I am going through it as I type this 600 miles from home.