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Q: Possible issue with the shift solenoid or TCM?

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My 2007 mazda 3 2.3 automatic is hard shifting followed by the AT light coming on. Hooked up to computer at O'Reilly and code is saying shift solenoid. Took to dealership they say transmission control module. Big difference in price, is dealer trying to take advantage of me? The guy I talked to at dealer didn't sound like he knew the difference

My car has 188000 miles.
My car has an automatic transmission.

It could be either one and it’s impossible to say without inspecting the car. The difference between the O’Reilly diagnosis and the dealer’s is probably one of equipment. O’Reilly uses a generic OBD-II scanner and the dealer should be using a factory designated unit. The difference in the information available to the different scanners is pretty big.

Additionally, the dealer has access to a database of failures in previous cars that are similar to yours so they may be diagnosing based on a pattern of failures. That doesn’t mean the dealer’s diagnosis is always right. It just means they are working from a bigger toolbox.

It wouldn’t hurt to get a third opinion, you can get one at home, by having Your Mechanic send a technician out to read your car’s diagnostic system and interpret the codes for you. Best of luck!

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