# Engine Coolant Temperature Circuit High Input (p0118)



## robcane (Feb 25, 2010)

I own a 1999 VW Passat 2.8l V6. The check engine light has been coming on periodically, the code is P0118 (Engine Coolant Temperature Circuit High Input). I looked it up and found this:
http://www.obd-codes.com/p0118
I was wondering what steps I can take to resolve this issue. Currently, the only symptom is that when I try to start the car the starter cranks normally, but the engine won't start. After a few tries of turning the key, it usually starts. Sometimes I wait a few minutes and try again. If the car has been sitting for a while (like overnight or a couple hours), the car starts fine and the check engine light doesn't even come on.
What's the worst case scenario? The car overheats without warning bc the temperature gauge is broken?
*The car has problems starting usually only when I am making frequent stops. Sometimes when the check engine light is on the car starts fine.
Thanks in advance for any help!


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## O_o (Nov 12, 2009)

*Re: Engine Coolant Temperature Circuit High Input (robcane)*


_Quote, originally posted by *robcane* »_What's the worst case scenario? The car overheats without warning bc the temperature gauge is broken?

No. The ECT sensor does not have anything to do with controlling the engine temperature. That's the thermostat's job. Of course, if your thermostat were stuck closed, you would not know you were overheating until it was too late if your ECT sensor were not working...

_Quote, originally posted by *robcane* »_the code is P0118 (Engine Coolant Temperature Circuit High Input). I looked it up and found this:
http://www.obd-codes.com/p0118

I think that code means the reference voltage for the ECT sensor is too high. Usually a fault in the ECT sensor circuit causes cold starting problems, but I'd start by checking that out anyway.


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## robcane (Feb 25, 2010)

Thanks .
I tried to check out the ECT, but its really tucked away behind the engine. I think I will have to take it to a mechanic tomorrow.


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## O_o (Nov 12, 2009)

*Re: (robcane)*

Yeah, it's not easy to get at, but if you remove the beauty cover and the flex hose coming out of your airbox, you should have enough room.


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## robcane (Feb 25, 2010)

*Re: ()*

I removed the flex hose, but I still need the hands of a 12 year old girl to actually reach it!


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## O_o (Nov 12, 2009)

*Re: (robcane)*

Hmmm... can't help you there. I have two boys.








Maybe it's a bit tighter in the Passat (?). I don't remember it being that bad on the A4, but we are talking several years ago now. I think I made a hook out of a coat hanger to yank the clips off, and then just grabbed it with some pliers.


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## robcane (Feb 25, 2010)

Do you know how I could find the ground for the ECM? 
Can't find it in the repair manual.
I think there may be a loose ground somewhere since the problem is intermittent.


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## O_o (Nov 12, 2009)

*Re: (robcane)*

Intermittent operation is a classic symptom of a fubar ECT sensor, but it doesn't hurt to check.
ECM? Is that a typo? I don't have the pin-out for either the ECM or the ECT sensor, but ground is black by international convention*. Other colors are occasionally used, but if you find a black wire and it isn't ground, then some engineer needs to be fired.
* DC circuits ONLY. Black is HOT in North American AC wiring


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## dkfackler (Feb 8, 2010)

*Re: ()*

Aren't the VW ground wires brown?
d


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## O_o (Nov 12, 2009)

*Re: (dkfackler)*

Yes, VW usually uses brown for ground when it's not black. Still, if there is a black wire, it must be ground.
I don't remember the difference, but I think black can be connected to a device ground/neutral/negative terminal, whereas brown must be connected directly to the chassis. Does anybody know for sure?


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