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Discussion Starter #1
I have a friend that has a 2008 Jeep Patriot. She went to the store then on her way home check engine light came on and started flashing and got the traction light came on. I went over had problem starting ,pulled code 335 crack sensor problem also C121C cleared codes got started drove to my shop at home. looked online and read others having same problem. they installed new crank sensor did relearn process and light stayed out and ran fine. I did the same thing it would work and drove fine throughout the day but when it set for 7hours or over night had same problem. It would crack and crack then start ran rough turn on check engine light then started blinking and traction light came then when to solid check engine light. had to let it run for awhile before I could clear codes. did this same thing about a week and a half everyday used my scan tool to do relearn, did the 70 then coast to 40 three times.tried all i read about. A friend thought it might be the computer loosing the memory on this setting. Has anybody else had same problem, I sure would appreciate any suggestions. Thank you
 

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Could be a bad PCM, or a wiring problem.

Someone who had a similar problem (c121c) found they could stall the engine by pulling on the wiring harness for the crank sensor:

 

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Here's the info from the manual on C121C:

C121C-TORQUE REQUEST SIGNAL DENIED
For a complete wiring diagram Refer to Section 8W.

When Monitored:
With the engine running.

Set Condition:
When the Powertrain Control Module indicates, for an extended period of time, that engine management relevant for Automatic Yaw Control/Traction Control System control can not be accomplished.


Possible Causes

ANTI-LOCK BRAKE MODULE

POWERTRAIN CONTROL MODULE
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Diagnostic Test
1. CHECK FOR A DTC C121C-TORQUE REQUEST SIGNAL DENIED
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NOTE: This DTC must be active for the results of this test to be valid and this DTC may set while driving under severe load conditions.


Turn the ignition on.
With the scan tool, read and record DTCs.
With the scan tool, read and record Freeze Frame information.
With the scan tool, erase DTCs.
Cycle the ignition switch from off to on.
Start Engine.
With the scan tool, read and record DTCs and monitor ESP Torque Request status.

Does the scan tool display: C121C-TORQUE REQUEST SIGNAL DENIED?

Yes

Go To 2


No

Refer to the INTERMITTENT CONDITION diagnostic procedure. (Refer to 5 - BRAKES - DIAGNOSIS AND TESTING)

2. CHECK THE POWERTRAIN DTCS
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With the scan tool, read and record Powertrain DTCs.

Were any Powertrain related DTCs found?

Yes

Repair the Powertrain System in accordance with the Service Information.


No

Go To 3

3. ESP TORQUE REQUEST SIGNAL
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Engine started.
With the scan tool, read the Allow ESP Torque Request status bit.

Was the Allow ESP Torque Request showing NOT set?

Yes

Replace the Powertrain Module in accordance with the Service Information.



No

Replace the Anti-Lock Brake Module in accordance with the Service Information.

Perform ABS VERIFICATION TEST. (Refer to 5 - BRAKES - STANDARD PROCEDURE).
 

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Discussion Starter #5
Could be a bad PCM, or a wiring problem.

Someone who had a similar problem (c121c) found they could stall the engine by pulling on the wiring harness for the crank sensor:

Thank you very much. I will give it a try. It is so strange that after I clear the p335 and the C121C codes I can drive around stop and go. no problem restarting, but after 6 or more hour the next time or day it takes a bit to start them codes. I was going to order a refurbished ECM from a good company lifetime warranty. Flagship 1.Thanks again
 
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