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Discussion Starter #1
Good evening everyone,
Just finished replacing my I4 engine for a lower mileage one. Prior to swappong enignes I had a CEL for the o2 sensors. After swapping engine and topping off all fluids replacing o2 sensors, I start her up and idled perfect till it warmed up slightily and the idle started surging. Jumping from 1200 to 2000 rpms. CEL came on and I got code P2185 Engine Coolant Temperature Sensor 2 Circuit High Voltage

I looked up videos. I'm not over heating of anything. Again it didn't do it prior to the swap. Any suggestions?

Thanks in advance

Anyone?
 

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Elvira - the car
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You don't need an overheating condition for this to happen. If the sensor outputs a signal that makes the ECU think the engine coolant is cold, even if it's warmed up,it will increase the fuel delivery to adjust. A cold engine needs more fuel so that sensor is calling for it.

Replace the sensor and that 1200-2000 rpm oscillating will probably go away.

It initially idled OK because the engine and coolant WERE really still cold. After warming up the Coolant sensor was fighting with the other sensors that were reading a warm engine.

The ECU was fighting to fix the problem.

Secondary problem might simply be air in the coolant. Swapping engine may have left air in system but you sound like you know what you're doing since you're swapping engines and all that. Might just be an oversight.
 

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Discussion Starter #3
Yea I've swapped engines before but never had an issue like this I "burped" the radiator twice to make sure. Topped off fluids. I will change the sensor once I get home. Thanks for the response.

Just curious, is it common for a sensor to fail from simply unplugging for an extended period of time? Car was without a engine for about a week since I was doing it after work on my little free time .
 

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Elvira - the car
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Yea I've swapped engines before but never had an issue like this I "burped" the radiator twice to make sure. Topped off fluids. I will change the sensor once I get home. Thanks for the response.

Just curious, is it common for a sensor to fail from simply unplugging for an extended period of time? Car was without a engine for about a week since I was doing it after work on my little free time .
I once had two fail within 2 months of each other, new. Your situation is not similar to mine but it might be since the sensor body was not submerged in coolant all that time (1 week or so) it may have been breached after drying out and replaced into the coolant.:dunno:

Simply unplugging shouldn't kill it unless the plug or wires broke.

I should add the failures were on a Volvo not a Honda. So it wasn't a Honda part problem.
 

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This code is for the coolant sensor at the bottom of the radiator. Make sure the wiring is OK and the sensor is plugged in tightly. It may just be a bad sensor. You may also need to do an idle relearn as well.
 

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Discussion Starter #7
So I put a new sensor and still have CEL along with the surging idle. Could doing a relearn get rid of the CEL?
 

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Isn't the radiator coolant sensor in charge of activating the fans only?

I thought the ECU took it's temperature data from the coolant sensor located on the block (The one that drives the dash temp too).

When I got my car it had the radiator sensor overridden (Harness has two wires and they were spliced together) and the fans were on 24/7 even with the AC off, my idle was not affected. I replaced it and fixed the harness and the only difference was my fans now work by temperature as they should with the AC off.
 

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Discussion Starter #9
I don't know what else it is. I'm not expert but not a novice. I put my scanner and that's the only that comes up. I clear the code with car off, CEL turns off momenteraly then don't back on.
 

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Elvira - the car
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Isn't the radiator coolant sensor in charge of activating the fans only?

I thought the ECU took it's temperature data from the coolant sensor located on the block (The one that drives the dash temp too).

When I got my car it had the radiator sensor overridden (Harness has two wires and they were spliced together) and the fans were on 24/7 even with the AC off, my idle was not affected. I replaced it and fixed the harness and the only difference was my fans now work by temperature as they should with the AC off.
I believe this to be true. I do not know which engine this is but most times the ECT (Egine Coolant Temperature) sensor that goes to the ECU is in the block or like some, directly in the thermostat cover or very near that position.

Do a search on that engine and see if it calls out another temperature sensor.
 

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Discussion Starter #11
According to the "GOOGLE" and Hayes manual , there is another temp sensor by the egr. From what I read that's through one that sends the signal to the temperature gauge.
 

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The one on the top of the engine is the Gauge sensor the one at the bottom of the radiator is sensor 2. Take a look at this video, it should answer your questions on location of sensor 2.

 

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The CEL is either bad wiring or a bad sensor, the sensor can be checked with a multimeter. The connector can have corrosion, or the wires are pinch in the harness. I would inspect the connector carefully and follow the wires back. At this point I would do an idle relearn as it is an easy procedure. The temp sensor should not cause the idle to be irregular.
 

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Discussion Starter #15
Finally got back on here, So I fixed my idle. Didn't have to do a relearn but I still do have the CEL for that sensor. So I'm guessing the wiring got bad somehow whenb swapping out motor. Sensor is new. Going to take it to a buddy of mine to see if he can fix that for me. But thanks for all the help guys. Thumbs up!
 

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Finally got back on here, So I fixed my idle. Didn't have to do a relearn but I still do have the CEL for that sensor. So I'm guessing the wiring got bad somehow whenb swapping out motor. Sensor is new. Going to take it to a buddy of mine to see if he can fix that for me. But thanks for all the help guys. Thumbs up!
Bro how did you get this fix? I have this honda accord 2006 that I just bought and I am having this p2185 and running very rough. I changed the radiator sensor and still the same problem please can you help me with a hint of how you fix yours? Thanks
 
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