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Drew, Super Mazda Tech.
Category: Mazda
Satisfied Customers: 2518
Experience:  19 yrs. experience. Mazda Senior Certified Tech, with Ford, Linc. & Merc. experience. ASE L1 Advanced Certified Master Tech.
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Mazda 3 S: Transmission shifts into 3rd gear while car is in

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Transmission shifts into 3rd gear while car is in motion, giving no warning of impending downshift. Two mechanics have read codes u0073 and u2516 while driving the car. Suspected turbine speed sensor and replaced it; with no change in car's operation. Inspected and cleaned electrical connections on PCM and TCM (without removing TCM); no discoloration or other visible signs of connection failure or short (i.e., twisted wires). Now I suspect TCM failure, but want to remove to visually inspect first. Ideas?
Welcome to Just Answer. My name is XXXXX XXXXX I will be glad to assist you.

I have replaced several of the TCM modules in these vehicles for these problems.

A U-fault code is not caused by a sensor but communication failure inside the modules.

I suggest just replacing the TCM and that should resolve the concern with your U-fault codes since you have already checked the other basic electrical connections.

If you ohm tested that CAN wires between PCM and TCM and are less then 5 ohms, then next step is to replace the TCM. You can also check for voltage at the CAN wires to the TCM. Test each wire should have around 2.5V with key on.

Please let me know if you have any additional questions by hitting the reply button.

Customer: replied 3 years ago.

Thanks. I haven't yet ohm tested any wires; I'm not sure I understand this step. How do I do this? It would seem to make sense with the parts disassembled. I'm confused, though, about how to do with the all the components reassembled (since you mention "2.5V with key on")?


Thanks again!



Hello Mike.

Lets skip the ohm test and just check for voltage first.

Disconnect the TCM electrical connector. Set your electrical testing meter to the 20V DC scale. Connect the black lead of your meter to the negative battery cable. WIth the key in the on position, engine off, use the positive meter lead and probe each CAN wire at the TCM electrical connector. There will be two CAN wires ( twisted pair ) and your meter should read close to 2.5V on each wire.

The CAN wires are pin# XXXXX and E.


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