Check engine and AT light on

purpleneko • 9 November 2019

Check engine and AT light been one for about a month now.    Started with slight jerks when shifting from park or neutral into drive or reverse; getting worse.  Stays in 3rd gear; mechanics say its not going into overdrive.  Changed transmission fluid and filter but lights still on.   My research on internet match symptoms to either the solenoid or automatic transmission module (ATM) needs to be replaced or fixed.  Read somewhere on net to try using manual mode to troubleshoot problem.  If manual shifting works, then it would confirm or rule out something but don't recall what the article said.  So yesterday I used the manual shifting and I was able to shift from gears 1 through 5 and engine did not rev. and both check engine and AT lights turned off!    Can't find that article/website info to read again. Does anyone have info on this?  Help needed in Hawaii!


There are a couple of things that could be going on here. The vehicle speed sensor that is in the transmission can be the problem. Or one of the solenoids that is in the transmission valve body is faulty.

I am glad that the reading online has helped you narrow down the problem. The next step in the diagnostics process is to either find a transmission shop that can read the fault codes for you. Or you can get a scanner online that will read transmission fault codes. Go to any of the marketplaces and search " Mazda Transmission Scanner" You will find a decent scanner for around $150.

Then use the OBD2 port under the dashboard to read the codes from the TCU. That will get you even closer to the cause of the problem. Let me know what you find out or if I can help in any other way.

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  • Hi Auto Service Genti!  Thank you so much for reading my call for help and a speedy response!  Okay, I will have someone read the fault codes and keep you updated.

    Aloha from Hawaii.

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  • Hey Mercedes Medic, will update once I get the code.    Using the manual mode is working not consistently. Now the gear number doesn't display on the dash (M1, M2, etc.) only the letter M.  Seems like manual mode is not working and when I put it in Drive, engine is starting rev at 3000 rpm so I go back to automatic.  Check engine and AT light still on.  Shifting getting clunkier with the car jerking when shifting into Drive.  Waiting for my mechanic to talk to his mechanics so they can troubleshoot and hook me up to get the code!  Stay tuned all  

    This is an awesome site.  Thanks!

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