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Discussion Starter #1
I have a 98 Camry 4cyl.

The car at times would not start and kind of backfire when attempting to start. I cant find the link but I found a post on here with all the symptoms a bad ect sensor would cause, and I found that I was experiencing most of them.

Car was having trouble starting, check engine light was on and I needed to smog the car in a few days. Which check engine light = auto fail at smog station.

So I purchased a OBD II scanner at Harborfreight on sale around $70. This one + 20% off coupon ;). I figured why not, and I was about to purchase a real expensive one off Amazon. $$$$$$

http://www.harborfreight.com/can-obd-ii-code-reader-eobd-scanner-98614.html

Code I got was P0115 Engine Coolant temperature sensor 1 circuit

So I cleared the code and went to parts store to get a new sensor. Car starts and ran fine for a week or so...

I then noticed a faint smell under the hood, like burning coolant. This was late at night when I got home after a 35-40 mile drive to my destination there and back.

Next day I take it for a short drive to get the car up to temperature and I notice the electric fans never came on. I turned on the AC and the fans would still not come on.

Next I disconnected the connector from the temp sensor in the radiator and turned the car on. Both fans come on and and run just fine.

Temp gauge never states the car is over heating, needle stays in the middle the whole time after warming up and driving around town.

With the HF OBD II scanner the live data option showed the temp rising up to 207 before I decided to turn the car off, and still no fans kicking on. I thought around 200 is when the fans normally kick on for this engine.

I took the car for a short drive to the post office down the street today (around 2 miles from my home). I park, go inside, then when I leave and get onto the street I feel a slight jerk and notice the check engine light popped back on. When I got home and scanned the car I get the same code again P0115.

I have to dig up the receipt so I can have the parts store give me a new sensor and see if that works. But this would not cause my fans not to work would it? I thought the sensor alone that screws into the radiator controls when the fans come on. To my knowleged if the fans come on with the connector removed the sensor in the radiator is good. And if the the sensor is bad the fans would stay on constantly??
 
G

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That depends on how the rad fan switch fails. If it fails open, then yes the fans would run constantly. If it fails closed, the fans will not run at all. With the AC on and still no fans sounds like a bad relay or poor ground connection.
 

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If you have a meter check the resistance across the the 2 prongs. Check it once, when the car is cool and again when the car is hot. The resistence should be higher/lower than the other when hot or cold. (I forget which way it works, but its basically how the sensor works to turn on your rad fan

Sounds like your troubleshooting steps are correct and you bought a bad ECT sensor or as suggested above a wiring/relay prob. I had a similar prob but not nearly as serious as yours. Check the link below, it helped me tremendously and sounds like everything you described.

http://www.obd-codes.com/p0115
 
G

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If you have a meter check the resistance across the the 2 prongs. Check it once, when the car is cool and again when the car is hot. The resistence should be higher/lower than the other when hot or cold. (I forget which way it works, but its basically how the sensor works to turn on your rad fan

Sounds like your troubleshooting steps are correct and you bought a bad ECT sensor or as suggested above a wiring/relay prob. I had a similar prob but not nearly as serious as yours. Check the link below, it helped me tremendously and sounds like everything you described.

http://www.obd-codes.com/p0115
The ECT sensor does not run the fans. The radiator fan switch at the bottom of the radiator operates the fans. The ECT tells the ECU what the coolant temperature is. This controls fuel trim for the injectors.
 

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Discussion Starter #5
Removed some tape from the ECT connector and found this.



I'm going to trace the wires back a little more and see what I find. Plan on making a trip to junk yard and see if I can find a better connector with around 12in of wire to splice back in. This may or may not be the issue.

I've only used a Multi Meter a few times in my lifetime. Have yet need to use one on my own car. I will head out and pick one up soon. What should I be setting it to?

Should I be grounding the Ground probe to the car, or to the cars negative side of the battery and then use the positive side of the probe to either touch the pins on the Senor its self and or the pins on the sensor connector?
 

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The way those wires are twisted up, they could be broken inside the green part of the connector. If they are, that's probably what's causing the P0115 code.

But, like 96paseo said, that sensor is not responsible for controlling the radiator fans. There is another sensor mounted in the radiator that does that. It's actually a normally closed switch. Closed when the coolant is cold, and open when it's hot. From what you said in your first post, I think it's bad. But you could check it easily. Use an ohm meter to see if it goes from closed to open when the coolant gets hot.
 
G

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Turn the ignition to "ON", then check the connector for 5 volts reference. If your not getting 5 volts, there's definitely an issue with those wires. They look pretty badly twisted up. I searched all over but couldn't find a replacement pigtail+connector for that sensor.
 

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I can't remember where we got them, but when I was working for Toyota, we had a kit of the male and female ends of the individual pigtails. I'll try and find something on e-bay (I need a kit for myself anyways).

Kinda like this, but both male and female, with 6" of wire of various colours pre-soldered to them.

 
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