Mazda 3. 2.0 GAS. Automatic transmission 4. Year 2004.
Sometimes when I drive AT comes on and transmission shifts in 3ed gear refusing to go up in 4 gear. if i stop for a while without turning off the car then AT goes off and transmission works properly. It can happen that I drive whole day without problem and the next day i get AT 3 times in a row.

Next to AT, check engine light also came on (which stayed). first I thought it could be the input turbine speed sensor but when I did computer diagnostic, it showed that the Camshaft position sensor was giving low signal. computer did not show any other problems.

Now, I am wondering didi any of you had similar problems with CAM sensor ?
Can CAM sensor really cause transmission problems and AT light on?

thanks in advance to all !

 

I wouldn't worry too much about solving everything at once. Transmissions are expensive, make sure your engine is running right first. Replace your cam position sensor, re-set ECU by disconnecting battery and stepping on brake pedal while cam sensor gets changed.
I've heard the throttle body acting up on automatic transmissions. Have you ever cleaned your throttle body or Mass Airflow Sensor? If not within last 2-3 years, do it now. Ever change your PCV valve? (this may not be related, but a must to do). If not within last 3 years, now is the time.
The other thing I would do is install an extra ground wire to the transmission and to the throttle body as well (from your negative terminal on battery - 12 gauge should suffice).

The above things are not costly and a good starting point. (not sure about PCV location on your vehicle though).

With your car being so old, mileage? Auto Tranny fluid should be changed at least every 50,000 miles (max).

 

thanks for the response,

1. regarding throttle body, I have cleaned it few months ago. When it was stuck the car was turning off itself while without pushing accelerator (e.g standing at the red light).

2. regarding PVC valve, I have not done it yet.

3. regarding the fluid, I have changed it and flushed 2 months ago.

4. regarding the extra ground wire, I can not figure out what you mean by it and for what can it be helpful? PLZ, explain a bit.

I have ordered the CAM sensor and will receive it in few days ,and I will replace it directly. Hope it will help. I just wanted to know if someone else had also CAM sensor problems and it had the same transmission symptoms ?

 

He means you should install an extra ground wire to these two places just in case your main ground wires have bad connections, its amazing how a bad ground wire can mess up a car.

 

+1 EXACTLY, Thanks.

 

thanks, now I get it sound pretty wise

 

Don't want to get you worried, but it's an uncomfortable coincidence that this started happening not too long after the fluid change. Was this a power flush? I'm not yet all that familiar with maintenance specific to Mazdas, but do know that a power flush is something to be avoided on many other higher mileage vehicles.

 

That and those "power flushes" are never recommended by the manufacturers, they even state do NOT get them and if you do you can void your warranty.

 

I am pretty sure that this problem was before I did fluid change. Perhaps I am not precise with timings. But the reason I did fluid change was AT an transmission problem. I thought that it might be time for fluid change.

regarding "power flushes", I did not do it. I have just let additional 4 liters of fluid circulate in the transmission, so I got sure that there was not left old fluid. I also replaced the filter.

Moreover, I have true feeling that it is not the tranny problem. It is something electrical. If I dont get AT on dashboard tranny shifts perfectly and functions perfectly. When I get the AT tranny goes in 3 gear, and I suppose this is kinda emergency option for the car telling me that something is not ok.

I should receive my CAM sensor today, and will replace it directly. I will let you know results.

 

I hope it's not too late. Was this your first change?
Mileage?