Bought a 2011 mazda cx7 2.5l sport less than 2 months ago. Within the past 3 weeks of driving, it wants to shift really hard into gears, and revs up high before shifting. Wont go into reverse. I changed the transmission fluid, and it shifted and ran fine for about a week, then went back to the same thing and wont go into reverse and is shifting hard in all other gears or revving up before shifting. Any ideas what it could be? Only code that pops up on obd is p0126, which is thermostat.

 

By discription only not the DTC the first guess is you have a transmission that was not serviced and likely has a substantial build up of varnish in the valve body and solenoids as well other parts .

If over 150k miles it’s not like a band-aide single fluid change will cure it.

You also did not state if you did a pant and fluid change or had a shop strive it on a professional transmission service machine.


As for your DTC I suggest going back into the ECU/PCM and retrieve more information you missed. Make sure it is not a blue tooth scanning software but a semi quality Manually connected directly to the OBDII Diagnostic Connector.