Transmission Control Module & Shift solenoid issues - Mazda3 Forums : The #1 Mazda 3 Forum
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post #1 of 3 (permalink) Old 03-10-2011, 07:57 PM Thread Starter
Bicycle Rider
Join Date: Feb 2010
Location: Midwest
Posts: 3
Transmission Control Module & Shift solenoid issues

Took my car (2006 with 5spd auto) to the dealer because CEL & AT lights were on and the gear indicator would stop working intermittently. This was Feb. 14th. Dealer informs me that it's the TCM, I authorize the repair ($1100). I pick up the car on Feb 16th and bring it back on the 18th for the same issue. Dealer informs me that the part is special order and will not be in until 21st or 22nd. I pick up the car on the 24th. Back to the dealer on the 25th. Picked it up March 8th at which point they explained the shift solenoid was also bad and that was what causing the original problem.

They tried to charge an additional $250 for replacing the solenoid. I politely declined to pay & after explaining why, the service manager agreed to waive the additional charges.

2 days later (today) and it's at the dealer again for the same issues.

I'm absolutely refusing to pay another red penny for this repair. It's been in 4 times now and never lasts more than 2 days when I get it back.

Any thoughts or suggestions?
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post #2 of 3 (permalink) Old 03-10-2011, 10:52 PM
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Join Date: Mar 2006
Location: St. Paul, MN
Posts: 3,486
Re: Transmission Control Module & Shift solenoid issues

IIRC there is no separate transmission control module; it's integrated in the car's main ECU. I would expect an ECU failure to cause problems other than just a couple indicator lights failing to work and the CEL and AT lights to come on. The price ($1100) sounds about right for a replacement ECU the end, my gut feeling is that they didn't diagnose your original problem thoroughly enough and suggested replacing the ECU on a guess.

Also, assuming the car was driving properly otherwise, a shift solenoid wouldn't be the problem. Shift solenoids are what makes the ATX shift through gears.

I'm thinking you have a problem with a sensor somewhere, or a wiring problem (pinched, corroded, etc.). Since the CEL and AT indicators are coming on, the tech should be able to read the error codes that the ECU is throwing and use them to diagnose the problem. Since it's a Mazda dealer you took the car to, hopefully the tech will finally have the intestinal fortitude to call the Mazda tech hotline for help with diagnosing. You might want to politely suggest they "call to see what Mazda thinks is going on with the car" to get the point across that you're tired of them guessing as to what the problem is.

Incidentally, how many miles are on your car, and how often (if ever) have you had the transmission fluid changed?

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post #3 of 3 (permalink) Old 03-10-2011, 11:38 PM Thread Starter
Bicycle Rider
Join Date: Feb 2010
Location: Midwest
Posts: 3
Re: Transmission Control Module & Shift solenoid issues

I apologize for not being more specific in my original explanation of the problems I'm experiencing with the car.

Did not mean to lead anybody astray or confuse anybody.Not to offend you or doubt your knowledge but the dealer called it a TCM, other members on the boards have called it a TCM as well. No mention of the ECU was made. I've nver read or heard that the two items were "integrated", on this site or anywhere else, that is news to me.

The issues were with the transmission, no sport-shift hard shift into reverse. I have read other posts on this board about similar issues most seemed to be related to the transmission electronics and not an indicator light failing to work.

The car currently has 81,000 miles I have had it since 59,000.

As far as the error codes go, although I did not see them first hand, I was informed it was a failure of the TCM not the ECU. 3rd time at the dealer I was told it was the shift solenoid that was burnt out/failed that caused the TCM (not ECU) to originally fail.
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