bradys007

P1725 recently came up on my OBD II my car shuts down, has a hard time shifting and will not start after the car stops without a battery disconnect. When the car does start it runs rough and makes a loud knocking sound. this has all happened within the last day 1999 ES 300. I am concerned that it is more than faulty sensors or wiring.

Please advise.

Thank you!

hzt30

P1725 - NT revolution sensor Circuit Malfunction

This sensor detects the rotation speed of the input turbine. By comparing the input turbine speed signal (NT) with the counter gear speed sensor signal (NC), the ECM detects the shift timing of the gears and appropriately controls the engine torque and hydraulic pressure according to various conditions. Thus smooth gear shifting is performed.

Trouble area:

Open or short in transmission revolution sensor (NT) circuit
Transmission revolution sensor (NT)

ECM

bradys007

With the situation of those controls being open or short. could that explain the knocking sound with loss of torque and delivery of pressure. as noted before I have a knocking sound. It actually sounds like a large exhaust leak pre-manifold. could the malfunction in the sensor or the system being open cause this failure as well as the vehicle shutting off?

Thank you!

hzt30

There are two speed sensors in the transmission:
1. Input Turbine Speed Sensor referred to as NT
2. The counter gear speed sensor signal (NC)

Since these are speed sensors and control transmission shifting I don't think it would cause rough running or shut the engine off. I have noticed another thread with the same P1725 code but the engine ran fine. I think that the engine shutting off might be a different issue. Did you check for pending codes?

https://www.clublexus.com/forums/rx-...hat-is-it.html

bradys007

The only other code that is pending is P0171 bank 1 too lean but that is intermittent and cycles about every 100-300 miles

hzt30

Will the engine stay running after you start it? When does it actually shut down?

bradys007

It stays running, but shuts down when the CEL comes on. Then refuses to start until battery disconnected, regardless of a clear for the codes. It does run like a typical P1725 error. but I have never known this to shut the vehicle down or cause an excessive back-pressure/popping sound.

Thanks

hzt30

Does the engine run smooth when it is running? How long does it stay running before the CEL come on? It could be a bad signal or ground that is shared to whatever causes the shut down.

bradys007

It did run smooth. I was driving it home from work and it died. the sound coming from the engine was like a really extreme misfire almost like there was no plug in one of the cylinders. It finally gave out on my way to the mechanic. and would not start. It seemed as thought it would not start as a precautionary failure. As i was towing it the battery died very quickly with just moderate use of brakes and hazards.

When it finally gave out the engine was very hot but did not register on OBD as over 212F and was below halfway on the cluster indicator. when I removed the dipstick to see if heat was damaging the oil smoke was released from the dipstick hole but oil was fine?????? hopefully I will find out today. I don't often take my vehicles to my mechanic but this cluster of problems has me stumped.