Hello! So my lexus has the codes P0125 and P0440. For the P0125 I was wondering where the Coolant Temperature Sensor is? Since my coolant levels are still full and seem to be fine, I figured it had to be the sensor.

 

Hello,

P0440 means there is a leak in an EVAP system, which could range from a loose gas cap to a leaking Charcoal Canister, which one is it you will have to find that out, it's impossible to tell anything without seeing the car in person unfortunately. This would be the first code I would diagnose before going to the other one.

P0125 code doesn't usually indicate a fault with a Temp Sensor in those cars, more often than not, it comes up if something is preventing the ECU from entering Closed Loop operation. Closed loop means that instead of utilizing a pre-defined operation charts, hard coded in the ECU, it works directly from the sensor operation, where MAF sensor to sets the initial amount, and A/F sensors are used as a feedback for that amount, creating a very precise system in any conditions.

In your case, there is something preventing the car from going into the Closed Loop control, from my experience, that code, could be a result of some glitch caused by ... cosmic radiation I assume, but if that's the case, it doesn't come back if you reset it, so that would be the first thing to try. If that won't help, it's often caused by a faulty A/F sensor, which can degrade over time. To see if that's the case, you will have to check Engine Live Data, A/F Sensor readouts should be close to, but not stuck on 3.2-ish volts, if you abruptly press the throttle, you should see the readouts immediately go to the Rich side, thay would indicate a working sensor.

Hope this helps and best of luck!

 

Hi There I just bought a 1999 RX300 and started feeling it was idling funny so I went to put my scanner on it and also got code P0125 but no check engine light. Has anyone had this problem and how did you get it fixed. Thanks so much in advanced

 

Well, usually that means a blown CEL bulb..

Hope this helps and best of luck!

 

Since the RX is new to you, please read through the user Manual.

On every start .. really before start as you move the ignition key from Lock-> Acc -> On/Run pause and check all the dash lights. The oil pressure, brake, check-engine warning lights should turn on [if I have missed any they will be listed in the owners manual]. This is very important step/confirmation that tells you that all the things that these light bulbs are monitoring are working. After few seconds these will turn off and specially after start [key back to run] these should stay unlit and if they do light up then you must explore the warning seriously.

If you were sold the vehicle by a licensed re-seller [not a private sale] then you have legal recourse [is it worth pursuing or not is up to you]. If it is private sale then you have reduced remedies.

Salim

 

Yeah, if you're reading codes but no check engine light, hmmmm

It might have been on so long the bulb burned out