Changed out my ect sensor but obd code p0115 persists

Hi all, so about a month ago my car (1999, Toyota Camry, 2.2L engine) started acting rather strange. I took it out for a drive and it began hesitating while accelerating, I was going about 60mph. As soon as I noticed this I pulled on an off road to turn around and head back home, but once I slowed down to make a u-turn, it stalled on me. I let it sit for a bit, and it started up again, but it was running high in idle. I was luckily able to get it home, even though it kept hesitating all the while.
I called up my dad because he knows a whole lot more about cars than I do, and he suggested I get an OBD sensor. Well I ran it and a p0115 code came back, from what I’ve read that means that there’s something wrong with the electronic coolant temperature sensor, or something in the circuit. As the title says, I changed out my sensor, but I still get the p0115 code. I took it out for another test drive to see if anything had changed, but all the same symptoms occurred.

So in all, it stalls when I decrease speed, hesitates at over ~20-30mph, and also high idles at around 2k rpm.

I’ve also read that it might be the thermostat or some malfunctioning wiring involved in the ect circuit, does this sound right to yall? I’m open to any advice.

I’d replace the thermostat.


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Is the engine overheating? Fault P0115 can occur if the engine coolant temperature sensor value is out of range (too hot). It is common to see these faults when there is no coolant in the system.

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I think you mean you purchased a scan tool, which said there’s a p0115 diagnostic code stored in your car’s computer memory. The engine coolant temp sensor is used by the drivetrain computer to set the fuel to air mixture. Engines need much more fuel when cold than warm, so if that sensor doesn’t register the correct coolant temp the computer won’t be injecting the correct amount of gasoline and poor engine performance could result. However, if engineis overheating, that will cause poor engine performance too. As mentioned above, ruling out engine overheating as the cause, that’s the first priority.

My guess, engine isn’t overheating, and the original ECT sensor was working perfectly. Problem is in the wiring between the sensor and the drivetrain computer. Coolant temp sensors usually simple thermistors, no moving parts and not a common failure item. Any engine compartment work done recently that required wiring be moved out of the way? Also check the faces of the associated connector for that sensor, maybe a pin/socket has pulled out or corroded.

Thermistors are pretty easy to bench test if you have an ohm meter and know how to use it. Google will tell you how to do it. I expect you’ll discover both the original and new one are working ok.


Nope, no overheating

Yeah, it’s a scan tool, I’m not sure why, but I always end up calling it an OBD sensor. I haven’t had any work done on my car recently, but I’ll be sure to go through and check the wiring and such.
Also I really appreciate the explanation of the system, I had a vague idea of how it worked before, so it helped me connect the dots.

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