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P2185 engine coolant temperature sensor 2 - circuit high

nadilos

New member
Location
Belgium
Car(s)
Golf 5 1.4 TSI
Hi

just bought a golf 5 1.4 tsi few months back for quite cheap. Had a few issues, fixed most of them but i'm still scratching my head because of the check engine light.

It gives me the following fault code:
- P2185 engine coolant temperature sensor 2 - circuit high

The fan still powers on and cools the engine down but not when the AC is on. That might be why my AC isn't working atm.

First thing I did was check the wiring and noticed some very dodgy wiring at the sensor. Did some wire work and replaced the sensor thinking that would make the dtc go away but no it keeps coming back.

Next thing I did was compare with another golf 5 of a colleague of mine because i'm not familiar with vw. Noticed a relay between the wiring on mine while the other golf had none (see picture). I don't know why it was placed there.

Car drives fine though and fan works.

Wondering if this could cause the dtc and how should I continue from here. Any help appreciated.

IMG_8442.jpeg
 

GTI's

Drag Racing Champion
Location
MD
Pull the wiring diagrams for the build date of this car and have a look at how it is wired.


Why is this plug missing wires


IMG_8442.jpeg
 

nadilos

New member
Location
Belgium
Car(s)
Golf 5 1.4 TSI
I removed the relay and put the wires back together as they should be. Now the fan just keeps spinning whenever the car is on. The check light is gone though.

The two coolant temp sensors are fine so that can't be the cause.

I even opened up the control module of the fan and everything seems ok inside nothing stuck or excessively dirty.

It seems the plug u highlighted is original.

Hmm what to do next? Just replace the fan control module?
 

GTI's

Drag Racing Champion
Location
MD
Look at the wiring diagram and find which wire is the signal wire to the fan control module make sure a signal is active on that wire. If the control module does not see a signal, then it will run all the time.


Yes, that connector highlighted is factory need to find out for what, Vw is not going to place a connector on a bracket for no reason.
 

nadilos

New member
Location
Belgium
Car(s)
Golf 5 1.4 TSI
Sorry for the late reply mate, couldn't find the time. Anyways, I found out that the connector is for the ambient temp sensor which is somehow missing. Could this be why the AC isn't working?

Concerning the wires, I did some multimeter back probing work and found the thick +red wire and small blue/red wire receive battery voltage. The yellow/purple wire gets a suspicious reading though, it receives 8v then drops to 5 then 3 and lastly OL on the meter. Then it jumps to 8 volts and drops again, It keeps repeating this. This yellow/purple comes from the motronic control unit so i assume it is a signal wire. Should I look for any disturbance in the wire? Is it acting up or normal?

Thanks
 
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