coolant temperature sensor circuit high

[grahamjf]

Hi all

Just had my 2005 Audi A4 2.0 tdi in for a diagnostic check at Audi and one of the fault codes said Coolant temperature sensor circuit high P0118.

I have changed that sensor and the thermostat 88 degrees before it went in, I dont understand the circuit high part of it.



The temperature gauge sits at 50 unless im booting the car up a hill, then it will go up a wee bit but wont reach the first notch. It's no where near sitting at 90 like it should be.



What is going on here?

[Okedokey]

Replace the IAT sensor.

[grahamjf]

Replace the IAT sensor.

Thanks for the reply
How would that effect the coolant temperature sensor?

Is that another name for the mass air flow?

[Okedokey]

No, that code seems to be more to do with the Intake Air Temperature sensor. https://www.ecstuning.com/Audi-B7_A4...ors/ES2800947/

However, the fact that your temp gauge sits at 50 is concerning. Do you have VCDS? It would be worth scanning the car more completely and posting the scan here.

[grahamjf]

Thanks for your help.

I will look into it, cant see vcds being more accurate than Audi tho.

Audi scanned the car they came up with the fault code P0118 Engine coolant temperature sensor Circuit High

The air temperature sensor fault code is P0113

Sounds more like a broken wire to the engine coolant sensor in the harness?

Thanks very much for your reply

[Okedokey]

https://www.obd-codes.com/p0118

Look at this. You're right, I tried to search earlier today and couldn't find anything.

[Theiceman]

if it moves when "booting up a hill" then goes back I doubt a wire is broken. Sounds like it is seeing a deflection , just not enough.

[grahamjf]

Thanks for the replies

What is a deflection?

[Theiceman]

deflection means the neddle is moving .. how much it moves means its deflection. point is its responding so a wire cant be broken.

What if its resistive , most thermocouplers are. what if you just shorted the wires together would the needle go all the way to the top ? or if you disconnected it . I don't know what would happen either way i'm just musing and trying to give you ideas of things to check.

[grahamjf]

ty very much for helping im going to try this test to c if the gauge goes all the way to the max i will report back soon ty

[grahamjf]

Just took off the plug and bridged the two pins and the gauge didnt even flinch.
Stayed below the 50.
I used a fused wire to check it.

My guess is that there is a fault with the wiring.

[Okedokey]

The post I linked above discussed how to check the wiring. Never short anything btw.

[grahamjf]

Thanks for the reply.

I'm not confident enough to go in about the pcm. I'll get someone who know's what there doing to check it