Hello, New member here.

My 2008 Mazda 5 with 69K miles has been great. Yesterday the AT light came on at 55 mph, and I felt and heard a CLUNK. I slowed down and it was fine. Then today on an uphill stretch it happened again at 40 mph.
The AT fluid level has always been good. I checked it again today and it is good.

The CLUNK kinda felt like it disengaged briefly and then re-engaged. Kinda like stepping on a clutch briefly in a standard shift car.
Any ideas? Is there any AT issues this model is known for? Any Service Bulletin etc?


Thanks for any help !

 

What condition is the ATF in? Is it dark? does it smell bad? How long since it was last changed? Have you had it scanned for fault codes?

 

Thanks grim reaper,

ATF color looks good.
I did not apply the sniff test.
I dont know if it was ever changed. Mileage is 69K.

I took it to my mechanic yesterday. He pulled P0720 Output Speed Sensor, and P0841 TFP Sensor Switch. He referred me to his Transmission guy. It goes in Monday. I asked...Should I wear a diaper when I go there?....He said....Well, no-o-o-o, probably not.

So far around town, its OK under 30mph. The CLUNKS were at 55mph and then at 40.

When I told my mechanic that I saw nothing in the owners maintenance schedule about changing ATF, he said it is not our grandfathers ATF, and it costs $16 per Qt. (hawaii). Usually it never needs changing...*they say*...he told me.

Googling those codes....transmissionrepaircostguide .com says:

P0720. The output shaft speed sensor is located nearest the drive axle, and is used by the ECU to monitor the speed/RPM of the transmission output shaft. A P0720 diagnostic trouble code gets stored when the data coming from the OSS sensor doesn’t fall within the ECU’s preprogrammed parameters.

P0841. An automatic transmission needs a certain amount of hydraulic pressure in order to move gears around and propel you down the road. A P0841 DTC means that the transmission fluid pressure sensor which monitors the hydraulic pressure inside of the transmission is not performing according to the preset parameters.

Lots more at Links:
https://www.transmissionrepaircostguide.com/p0720/
https://www.transmissionrepaircostguide.com/p0841/

Until Monday's shop stop...Stay Tuned.

Thanks again!

 

Well,

Trans guy scanned it, and drove it around town. No code, no issue on road. He talked to his friend that found the 2 codes. They were erased or reset.

It has not happened again during a week or more of daily driving.

Trans guy said if the issue becomes a problem it will need a new (or used) TCM.

He said if it was his car, ....(*he would not buy a Mazda in the first place*)... But if it was his, we would keep driving it, and be on the lookout for a used TCM.