Transmission not shifting properly and code P1725

Good afternoon,

What is the code number that came up?

Did you check the fluid level?

How long since you changed the oil, filter in the transmission?

https://www.2carpros.com/articles/how-to-service-an-automatic-transmission

The fact that will not move means either the level is too low, the filter is clogged or there is internal failure in the transmission.

https://www.2carpros.com/articles/automatic-transmission-problems

Roy

Reconfirm the code. P1201 is not listed in our database nor in generic OBD-II code list.

Symptom indicates the OD is most likely not engaging. Does manually turning the OD OFF and ON switch makes any difference to the engine rpm?

If P1201 is the confirmed code, that would mean a fault with the PCM as any code not listed means the PCM is faulty.
Electrical problems can be affected by disconnecting the battery, low or excessive charging. Power surge can damage PCM too.

I would suggest getting another scan done to check for trouble codes.

When the O/d switch fails to work, it could mean the transmission valve body has a fault.

Apart from checking fuses, I would suggest checking the ground circuits. If any is poor, especially for the transmission and its control, it can cause erratic shifting patterns.

TY for the donation

Get the coolant temperature, throttle position and vehicle speed sensors tested thoroughly if they all okay -could be coming from the internals of the transmision-which probably needs to be pressure tested to identify the problems.

The computer uses this input signals from this sensors to command and control the upshift/downshift/overdrive/lock-up thru shifting solenoids.

P0171 and P0174 are system running lean conditions. It could be vacuum leaks or a host of sourves and does not indicate what component is faulty. It could also be due to low fuel fuel pressure or caused by the knock sensor.

P0320 and P0325 - Knock sensors fault, left and right bank respectively.
Knock sensors failure are common for such vehicles.

All the 4 codes have no relations to the transmission not shifting to O/D which can be due to a fault with the O/D solenoid stiicking.

Sometimes problems are coincidental and you should not keep thinking it is related to the alternator replacement. Test the O/D solenoid first.

Yes, OD is 4th gear and can be manually turned off with the switch on gear shift if it is working correctly.

Yes, that is the situation it should be.

When you hit the button and if the O/D OFF light comes on (ensure the light comes on), the rpm should increase as the gear downshifts. If there are no changes, that means the transmission is in 3rd speed which runs at a higher rpm.

If you have a scan tool, that would be easy to test the solenoids. Usually when a solenoid fails, the transmission would go into limp mode and the MIL would indicate. You were not able to retrieve any trouble codes for transmission failure so there is a possibility the problem is with the transmission manual controls such as shift valves or clutches.

I could find not any relations to the knock sensor and engine going into limp mode. So far all the vehicles I have repaired regarding knock sensor problems have never had any complaints of the O/D not working nor of vehicle going into limp mode.

What the engine control system does is to retard the ignition timing and that would affect engine performance.

Whether the explanation given is true or not, let us put it aside first. Since the knock sensors are bad, have them rectified first and check the engine coolant level. Overheating is the most common cause of knck sensor failure.

Once the knock problems are resolved, we would know if the O/D not working is linked to it.

Before attempting repairs, clear the codes and go for a test drive first to check if the codes comes back. Try to drive with gradual acceleration to avoid pinging so that you can test the transmisison first.