Come along with Eric O. as we dive into this intermittent complain of "some light on the dash comes on and my car shifts hard." Looking at the code history and seeing a rash of no com codes it doesn't take us long to find the bad connection dropping out the CAN. We just need to determine if it is a bad connection or a bad wire. -Enjoy
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OTC (3415) CAN Test Box - Breakout Box and Protocol Detector:
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50 thoughts on “Chevy cobalt: trac light on, harsh shifting and no com w/ all modules”
  1. Avataaar/Circle Created with python_avatars Adrian Martinez says:

    Tengo un problema similar con mi carro

  2. Avataaar/Circle Created with python_avatars willy68057 says:

    Same issues filter was clogged changed it and flushed it works great

  3. Avataaar/Circle Created with python_avatars joe mamma says:

    same problem changed the fluid and filter than flush it out worked for me. Might not work for but did for me

  4. Avataaar/Circle Created with python_avatars Cars says:

    Deoxit = The best contact cleaner available= had a friend with a Cavy and the ABS light would come on whenever the humidity was high. Turn off the engine to reset the warning and the next day same problem. Cleaned the contacts on both front wheel ABS sensors and no problems for ten years now.

  5. Avataaar/Circle Created with python_avatars JohnnyLightning says:

    The ground on the front of the transmission is bad. They have 6 ground wires all going to one flimsy connector that over time gets corroded and looses connection.

  6. Avataaar/Circle Created with python_avatars Jose Pizarro says:

    Thanks for your video

  7. Avataaar/Circle Created with python_avatars ADD Me Ons😁 says:

    I have a 2010 cobalt and randomly when I slam on the brakes, the trans will start to kick when shifting 2nd gear. Its and automatic and this doesnt always happen. After turning it off and turning it back on this issue may go away until I need to slam on the breaks again.. what is it?

    Chevy says trans solenoid?

  8. Avataaar/Circle Created with python_avatars Kelly Klein says:

    Thanks for pinpointing this issue.
    I looked for the same harness and the wires where tightly kinked over. I disconnected the harness and turned the key on. The tracktion control light was off, so I think two of the wires were effected from stretching. I put it back together without siting the harness back on bracket and no trouble

  9. Avataaar/Circle Created with python_avatars Kelly Klein says:

    Same thing on a hhr. Track control light comes on transmission runs harsh. After vehicle sits for a little while, everything works ok on a restart.

  10. Avataaar/Circle Created with python_avatars J Newell says:

    I have the same issue, comes and goes. Mine also shakes horribly at 55 to 60. Have replaced everything in the front end so I'm assuming the electric power steering has the issue. But if you YouTube that job its a bit more then I'll attempt alone. Did these issues ever reveal themselves later down the road?

  11. Avataaar/Circle Created with python_avatars Alex Gonz says:


  12. Avataaar/Circle Created with python_avatars Virginia Hardy says:

    My Cobalt only throws a traction control & abs light when it’s barely above freezing after a wet day. Also while sitting still at a traffic light or parking space. Never does it while moving & it locks the call until you do 2 starts, then it acts like nothing ever happened. Corroded wheel sensor? Note you only have voltage while the car’s moving, not still. Could be the traction control has a poor ground or something else going on. In warm weather, it’ll never do it.

  13. Avataaar/Circle Created with python_avatars crlaw75 says:

    My kind of vehicle; plain, without all the computer and tech crap on vehicles today.
    The problem is a lot of those vehicles are rusting or scrapped.

  14. Avataaar/Circle Created with python_avatars Terry See says:

    Thank you for your video, it is nice to see a technician instead of a parts changer , I subscribed to your publication, thanks again

  15. Avataaar/Circle Created with python_avatars Brandon McNeely says:

    My 06 HHR is doing the same thing harsh shift and abs traction light coming on then going back to normal then coming on again . No check engine light .

  16. Avataaar/Circle Created with python_avatars Martin Kucic says:

    Oh Hell No! You can do it but I wanna put a bullet in my head!!
    How do you charge the customer for that? I need to go to school.

  17. Avataaar/Circle Created with python_avatars Carrie Petiprin says:

    Did this solve the issue for the vehicle owners? I am currently dealing with the exact same issue with my Chevy Cobalt. Same kind of car manual windows and locks. All the gauges will start wigging out and the transmission will shift really hard. I've taken it back and forth to my local Chevy dealer for the past 3 years for the same issue. This week alone I have paid out $460 to replace parts and then they came back and said that it is a computer issue that is going to cost me another $890. It will be at least 10 times or more that I have taken the vehicle in to have the same exact issue fixed. My local Chevy dealer ordered the computer and are planning on installing it Monday. Do you have any advice to offer me?

  18. Avataaar/Circle Created with python_avatars hi says:

    Best advice is don't buy a chevy

  19. Avataaar/Circle Created with python_avatars Notquiteultralight says:

    “Its been touched”🤣

  20. Avataaar/Circle Created with python_avatars Shaun Deleon says:

    And is it pricey?

  21. Avataaar/Circle Created with python_avatars Shaun Deleon says:

    My car is doing this same problem ? I have a awsome master mechanic should I tell him to do the same check you are so he can trace it down?

  22. Avataaar/Circle Created with python_avatars Bill Wilson says:

    I just repaired a slowbalt that would randomly die and restart after 20 minutes or so by replacing the negative battery terminal. The factory ones are crap and wouldn't tighten completely. it displayed codes p0606. p0700, p0335, u0100

  23. Avataaar/Circle Created with python_avatars Kelcey Spackman says:

    I have the same problem going on with my cobalt. Did this car ever return?

  24. Avataaar/Circle Created with python_avatars the big dog angel says:

    Hello Erica your video came up on my YouTube channel cuz I'm trying to figure out a problem with my mechanic it's actually touched on a few basis but I just wondering if we want to run by this to you a couple days ago my Chevy Cobalt I was driving and everything around like I normally do every day and find when I came home turned it off and then turn off and I had to turn the key back on to the on position to turn it off now the power steering on the cluster came on says power steering the traction control light came on I knew a couple of the fuses were blue blue on that interior so I redid those when was blown under the junction box I redid that but went back out there today still doing the same thing and now my engine light and airbag light is indicated when the car is completely off in the keys out of the ignition it's throwing a p1682 code but we have a feeling it's electrical but since we've been watching your videos last couple days trying to figure out what is wrong with it you know you seem like the closest person to the problem I appreciate if you can get back to me as soon as possible and let me know what you think or what the problem

  25. Avataaar/Circle Created with python_avatars the big dog angel says:

    Can you please reply back to me or message me personally I'm having kind of the same issue I started two days ago my engine light came on my power steering light came on on the you know the cluster saying power steering and then my traction control light came on and I put hook up my scanner through a p1682 and then I checked a couple of the fuses in the fuse box there is a couple you know blown I replace them and the other thing is when it shows that code and the problem when I turn my key on the car starts when I turn the key off the car still on until I turn it back on you know what the key position and I'm lost for words

  26. Avataaar/Circle Created with python_avatars Somethings cantbefixed says:

    I think there was a recall for this problem

  27. Avataaar/Circle Created with python_avatars Garth Clark says:

    I have to wonder what some of those other shops would have done with this issue. Those who convince customers to pay for parts replacements. And a week or so later, the car comes back with the same problems, they do the same thing again by chucking parts are it. As I know it, a shop shouldn't get paid for things they do that doesn't correct the problem, only the thing that does yet shops collect undue fee's from their customers. Interesting how that occurs to way too many customers while Eric does his diagnosis for a one hour shop charge (in most cases) then explains to the customer what he has found and which path to take in correcting the problem. I wish there were more shops and dealerships who would perform their diag the same when they really can't make the call with 100% certainty. Too bad some of these connections and termination issues can't be taken to the manufactures and say, "hey, these parts are failing by defect in design", buy the car back until you learn a few lessons about design/dependability engineering in electronics.

  28. Avataaar/Circle Created with python_avatars Mathew Bolt says:

    Is this Eric the car guy but on a different channel?

  29. Avataaar/Circle Created with python_avatars Jack Harris says:

    Eric: Many years ago IBM looked for cold solder on PC boards by operating them with elevated heat on a vibrating table.  Eliminated many failures in the field.

  30. Avataaar/Circle Created with python_avatars hellship rc says:

    Im willing to bet the storage drawer/trunk release has been moving or digging into that harness. As soon as i noticed mine was doing that I taped my harnesses out of the way.

  31. Avataaar/Circle Created with python_avatars justsomeguytoyou says:

    A very interesting case. It's been over a year, did the customer ever bring it back for the same issue?

  32. Avataaar/Circle Created with python_avatars Tbone productions says:

    Crazy thought here, is there any talk in the industry of fiber optic cables replacing copper wires? Just wondering

  33. Avataaar/Circle Created with python_avatars Danny Wojkiewicz says:

    I have a 97 Chevy Cavalier has a anti-theft light that comes on when it's cold and it won't start until it warms up need help

  34. Avataaar/Circle Created with python_avatars Mike Chiodetti says:

    Oh ya, Great Video! Keep up the good work!

  35. Avataaar/Circle Created with python_avatars Mike Chiodetti says:

    My 06 Nissan Frontier did the same thing, the "U" code was the 4WD module under the dash. Cleaned the connections, problem solved. Network's happy, no problem with the 4WD module before and after cleaning and the code hasn't come back. Love those intermittents! They are the curse of the automotive industry!

  36. Avataaar/Circle Created with python_avatars Peter MacKay says:

    I have a 2007 Cobalt, very similar to this one you show. I get the same symptoms in the rain. When it's dry all is good. In the rain I get the codes. I've had it happen a few times. Usually it happens just when i start the car. Recently it's happened while driving. The car goes into low power mode.

  37. Avataaar/Circle Created with python_avatars Vita Vas says:


  38. Avataaar/Circle Created with python_avatars Anthony Perez says:

    My 2006 cobalt is giving me the same problem i found the maf sensor pigtail with a ripped wire i replaced then i found my exhuast actuator pigtail ripped the t/c light shut of for a day then came back on ever since and now wont even shut off i need help please

  39. Avataaar/Circle Created with python_avatars Joe Bucci says:

    At the dealership we the database tool. We can see what module are on line and which are not. The first thing I do I check resistance at the dlc connector then go from there. Split the system in half check for 120 ohms, then move Towards the side that doesn't have 120 ohms. You know the rest.

  40. Avataaar/Circle Created with python_avatars hammer head says:

    Another thing. When you break out the schematics and go through them step by step during your troubleshooting routine is priceless. I have learned a ton watching your troubleshooting methods. A million thanks to you. And again, Kay Man scared the hell out of me, LOL!

  41. Avataaar/Circle Created with python_avatars hammer head says:

    Another great diagnostic video, thanks again. Loved the comment by Kay Man.

  42. Avataaar/Circle Created with python_avatars Danny C says:

    Mr. O, you would make an excellent instructor at a tech school.

  43. Avataaar/Circle Created with python_avatars Donald Pauli says:

    Manny. Yes it is but when diluted properly with alcohol, one small bottle will last years

  44. Avataaar/Circle Created with python_avatars mikerivera09 says:

    Cobalts had a power steering motor recall. Maybe when/is the recall was done something got screwed up when/if the tech unplugged that connector. Not a Chevy tech. Toyota tech here. But I owned a cobalt with that recall.

  45. Avataaar/Circle Created with python_avatars fishhuntadventure says:

    This is why I drive a 1989 jeep. There’s a lot less mysteries installed at the factory.

  46. Avataaar/Circle Created with python_avatars Donald Pauli says:

    There is a product called Stabilant 22 used in the electronic industry that goes a long way to improve conductivity with slip together connections and terminal contact areas