C7 acting crazy….bad ground??…. HELP
Thread Starter
Heel & Toe
Joined: Jan 2024
Posts: 17
Likes: 0
From: Atlanta
C7 acting crazy….bad ground??…. HELP
I have a 2014 C7 base auto. Recently it has been acting crazy randomly. One minute it’s fine, the next it has hardly no power, no back up camera when in reverse, active exhaust will not work, you cannot tell what gear you are in (does not display the P, R, N, D) shifts super rough and throws the CEL with another weird light at the top of the cluster that almost looks like a wrench.
CEL is U0101- Permanent: Lost Communication with transmission control module. DTC Severity 2 of 3: this fault may pose damage to components and should be repaired as soon as possible.
P26C8: Chassis Control Module Requested MIL Illumination
P050D Permanent: Cold Start Rough Idle
im thinking it is a loose or corroded ground, but I don’t know where they all are located. As mentioned, it will drive fine, flip out like this for 5-10 mins, then back to acting fine. Any ideas???
Thank you!!
CEL is U0101- Permanent: Lost Communication with transmission control module. DTC Severity 2 of 3: this fault may pose damage to components and should be repaired as soon as possible.
P26C8: Chassis Control Module Requested MIL Illumination
P050D Permanent: Cold Start Rough Idle
im thinking it is a loose or corroded ground, but I don’t know where they all are located. As mentioned, it will drive fine, flip out like this for 5-10 mins, then back to acting fine. Any ideas???
Thank you!!
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,643
Likes: 4,082
From: Cape Coral, Florida
With the “U” code sounds like a possible communication issue…I don’t know what mechanical or electrical abilities you possess but if it is a communication issues 999 out of a 1000 repair shops or dealerships would have no idea and how to even begin to diagnose this…how old is your battery ??…I always start a diagnosis with a battery check…you will need a factory level scan tool to see if you can communicate with the TCM when you are having issues…unfortunately it’s not a blown fuse.
Thread Starter
Heel & Toe
Joined: Jan 2024
Posts: 17
Likes: 0
From: Atlanta
With the “U” code sounds like a possible communication issue…I don’t know what mechanical or electrical abilities you possess but if it is a communication issues 999 out of a 1000 repair shops or dealerships would have no idea and how to even begin to diagnose this…how old is your battery ??…I always start a diagnosis with a battery check…you will need a factory level scan tool to see if you can communicate with the TCM when you are having issues…unfortunately it’s not a blown fuse.
I just didn’t know if a ground could be loose or dirty to cause this. It’s weird it runs find sometimes, and sometimes it acts completely crazy.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,643
Likes: 4,082
From: Cape Coral, Florida
No need to worry about the P26C8...it is an informational DTC only...read the NOTE below.
Diagnostic Aids
Communication codes, U-codes, as well as powertrain codes, P-codes, set in the chassis control module will cause the chassis control module to request DTC P26C8 to be set in the ECM.
Reference Information
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions See: A L L Diagnostic Trouble Codes ( DTC ) > Diagnostic Trouble Code Descriptions > Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References See: Vehicle > Programming and Relearning > Control Module References for scan tool information
Circuit/System Verification
Note:
* Do not replace the engine control module for this DTC. DTC P26C8 is an informational DTC.
* Correct any engine control and communication DTCs before diagnosing chassis control module DTCs.
Diagnostic Aids
Communication codes, U-codes, as well as powertrain codes, P-codes, set in the chassis control module will cause the chassis control module to request DTC P26C8 to be set in the ECM.
Reference Information
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions See: A L L Diagnostic Trouble Codes ( DTC ) > Diagnostic Trouble Code Descriptions > Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References See: Vehicle > Programming and Relearning > Control Module References for scan tool information
Circuit/System Verification
Note:
* Do not replace the engine control module for this DTC. DTC P26C8 is an informational DTC.
* Correct any engine control and communication DTCs before diagnosing chassis control module DTCs.
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Thread Starter
Heel & Toe
Joined: Jan 2024
Posts: 17
Likes: 0
From: Atlanta
So you’re saying I cannot access this ground or is just need to remove the wheel and fender well trim to access it?
Thread Starter
Heel & Toe
Joined: Jan 2024
Posts: 17
Likes: 0
From: Atlanta
Thread Starter
Heel & Toe
Joined: Jan 2024
Posts: 17
Likes: 0
From: Atlanta
No need to worry about the P26C8...it is an informational DTC only...read the NOTE below.
Diagnostic Aids
Communication codes, U-codes, as well as powertrain codes, P-codes, set in the chassis control module will cause the chassis control module to request DTC P26C8 to be set in the ECM.
Reference Information
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions See: A L L Diagnostic Trouble Codes ( DTC ) > Diagnostic Trouble Code Descriptions > Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References See: Vehicle > Programming and Relearning > Control Module References for scan tool information
Circuit/System Verification
Note:
* Do not replace the engine control module for this DTC. DTC P26C8 is an informational DTC.
* Correct any engine control and communication DTCs before diagnosing chassis control module DTCs.
Diagnostic Aids
Communication codes, U-codes, as well as powertrain codes, P-codes, set in the chassis control module will cause the chassis control module to request DTC P26C8 to be set in the ECM.
Reference Information
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions See: A L L Diagnostic Trouble Codes ( DTC ) > Diagnostic Trouble Code Descriptions > Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References See: Vehicle > Programming and Relearning > Control Module References for scan tool information
Circuit/System Verification
Note:
* Do not replace the engine control module for this DTC. DTC P26C8 is an informational DTC.
* Correct any engine control and communication DTCs before diagnosing chassis control module DTCs.
okay cool. Thank you!
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,643
Likes: 4,082
From: Cape Coral, Florida
These G401 grounds that are also on the C5 and C6 are usually on the frame rail…you can look there…BTW, the odd numbered grounds are on the left side of the car and G4XX are in the back…G1XX are in the engine bay.
Thread Starter
Heel & Toe
Joined: Jan 2024
Posts: 17
Likes: 0
From: Atlanta
thank you so much for the help! I will crawl around the drivers side and try and locate all the grounds to clean them and make sure they’re tight.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,643
Likes: 4,082
From: Cape Coral, Florida
I wouldn’t waste your time cleaning all these grounds…concentrate on the ground that may be causing your issue…they should be clean and not just tight…are you using a code reader ??
Thread Starter
Heel & Toe
Joined: Jan 2024
Posts: 17
Likes: 0
From: Atlanta
Le Mans Master
Joined: Jun 2019
Posts: 5,503
Likes: 2,202
From: Loveland
Look at this thread, it has the correct specs for the battery. Some are in/lbs some are ft/lbs.
https://www.corvetteforum.com/forums...que-specs.html
https://www.corvetteforum.com/forums...que-specs.html
Thread Starter
Heel & Toe
Joined: Jan 2024
Posts: 17
Likes: 0
From: Atlanta
Look at this thread, it has the correct specs for the battery. Some are in/lbs some are ft/lbs.
https://www.corvetteforum.com/forums...que-specs.html
https://www.corvetteforum.com/forums...que-specs.html
Nice! Thanks a lot
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,643
Likes: 4,082
From: Cape Coral, Florida
The wrench symbol usually means you have scheduled maintenance or a Powertrain or Transmission issue…my motto is “test don’t guess” so I can’t say for sure what your issue is…below are all the various circuits on G401…your NPP exhaust is one of those grounds…the “Prindle” as we call it may be related to the TCM no communication…I think the Innova should be able to read TCM codes so when it starts going haywire see if you can read “live data” in the TCM or that you can communicate with it…look at the other circuits on G401 and see if they too are affected…it may be shifting rough because of the VSS (vehicle speed sensor)…the car won’t shift right if the ECM does no the cars speed.
Thread Starter
Heel & Toe
Joined: Jan 2024
Posts: 17
Likes: 0
From: Atlanta
Man I really appreciate the documents! I can’t wait to get to work on the car. I will update you on what I find. I will probably tear into it tomorrow or the next day after work.