CEL and radiator fans running constantly

[catfood12]

After around 700 miles of mainly motorway driving last week, I got a CEL. Also noticed that the radiator fans were running constantly. That was when I arrived home after a long drive, not stuck in traffic. Same next morning from cold, CEL and fans running constantly. Van still ran well, it did take ages to warm up next day though.




VCDS gave me this;



Engine ECU showing this;



Then when a bit more warmed up.



Then completely lost the plot!




Looks like the G83 sensor on the radiator hose has failed. I think we can rule out wiring or the ECU with those values.

Looks like it's a 06A919501A. Mentioned on a few other threads too.

Location of Engine Coolant Temperature Sensor.

Can anyone tell me location of the “Engine coolant Temperature Sensor” on the 204 engine please. My temperature gauge started playing up yesterday and I’ve got a fault code “00522 Engine Coolant Temperature Sensor (G62). I’ve searched the forum, googled it and searched on YouTube and had no...

www.t6forum.com

Lots of chat on other VW forums too, looks like a common part.

£52 incl VAT from the main dealers, but they don't have the sealing washer in stock that needs to be replaced at the same time.

£54 from TPS. Not sure why more expensive.

Pattern part, £10 from the Amazonians. Will be here tomorrow.

Grey 2 pin Water Coolant Temperature Gauge Sensor 06A919501A Temp Sender Clip & O ring Compatible with VW Group Vehicles Skoda SEAT etc. : Amazon.co.uk: Automotive

Buy Grey 2 pin Water Coolant Temperature Gauge Sensor 06A919501A Temp Sender Clip & O ring Compatible with VW Group Vehicles Skoda SEAT etc. at Amazon UK. Free delivery on eligible orders.

www.amazon.co.uk

 

[catfood12]

Oh well. It wasn't the sensor. Changed sensor, just the same. Too hasty with my ruling out the wiring.





Tried shorting pins etc, and I see a difference in reported temperature. Went down the wrong rabbit hole until I realised that the brown wire isn't actually a ground, but a reference from the ECU. I'm looking at G83 on the right....



Brown wire, ref 275(circuit 69), then appears as wire 69 (circuit 275) later on;



I guess Ping 15 on the ECU gives some stable reference for all of those sensors. The ECU goes to -40 degrees, which is open circuit, regularly. Looks like a loose connection somewhere. Lots of wiggling hasn't been able to provoke it yet.

Next stop is battery out I guess to get to the ECU in the E-box.

Trying to find any of the other sensors, or the loom connector (D121) to test from. This wouldn't have happened to Diagnose Dan.

 

[Pauly]

What document/page are those diagrams from ?

 

[Loz]

D121 features here;

 

[Pauly]

What engine @catfood12 ?

 

[catfood12]

What document/page are those diagrams from ?

It the 2.0 EU6 Diesel wiring diagram here;

https://www.t6forum.com/threads/2-0-diesel-eu6-engine-wiring-diagram.28944/

Pages 6 & 21.

D121 features here;
View attachment 150477

What doc is that ? I can't seem to find it on here.

What engine @catfood12 ?

I have an EU6 204... Not sure what code that is. 2017 PV LWB 2WD.

 

[Pauly]

Any progress ?

 

[catfood12]

Any progress ?

Not yet. There's so little space to try and get to things. I haven't pulled the battery out to get to the E Box yet.


Did you manage to find any docs showing sensor locations, or location of this connector D121 Pauly ?

 

[Loz]

Not yet. There's so little space to try and get to things. I haven't pulled the battery out to get to the E Box yet.


Did you manage to find any docs showing sensor locations, or location of this connector D121 Pauly ?

D121 is unlikely to be a connector, it could simply be a splice in the loom.

 

[Pauly]

I would agree that it will be a splice inside a taped up loom

Could you test between pin 2 of the coolant temp sensor against pin 1 of any of the other sensors connected to D121, guessing G71 intake manifold sensor may be the easiest to access
You may be able to prove wiring integrity through the brown cores ?

I do think ultimately you are going to have to get the battery out and open the ebox, both sides of that plug run back to T10g which is inside the ebox

 

[catfood12]

I would agree that it will be a splice inside a taped up loom

Could you test between pin 2 of the coolant temp sensor against pin 1 of any of the other sensors connected to D121, guessing G71 intake manifold sensor may be the easiest to access
You may be able to prove wiring integrity through the brown cores ?

I do think ultimately you are going to have to get the battery out and open the ebox, both sides of that plug run back to T10g which is inside the ebox

That's exactly what my next step is, but I can't physically find G71!

 

[Loz]

That's exactly what my next step is, but I can't physically find G71!

right on the top, 20 in this pic.

 

[catfood12]

right on the top, 20 in this pic.
View attachment 151182

Sadly not I think. Cable colours are wrong. I think that above is G42;



G71 is described as inlet manifold pressure sensor, so I think it's measuring boosted air, can't see all of the manifold though under the layers of other plumbing and wiring.

 

[Loz]

Except the diagram suggest its a combined sensor.



The one that on the manifold is a different sensor.

 

[catfood12]

Soz @Loz, you're right, that is G71, I was looking at the other sensor. Thanks for digging this out.

Finally back after Easter break, and this was first job on my to do list.

Tested continuity between the brown wires on G71 (Intake manifold sensor) and G83 - the rad outlet temp sensor that I have a problem with.

G71;



Paper clip to make contact on G71, as I don't have anything more professional looking.

Similar on G83;



Open circuit.




Double checking my paperclip connectivity by back probing with the thinnest thing I have (an old set of BOC welding torch jet reamers), as a paperclip wouldn't go in, which was OK;



Same down below.



I wanted to double check what's being seen at the ECU, so opened up the ebox.

More paperclips;


Pin 15 on the 96 way connector.

Same. Open loop to the temp sensor;



Continuity to the manifold sensor;



As discussed earlier in the thread, the D121 crimp or joins are internal to the loom. The temp sensor is on the last leg to the ebox, but I don't fancy stripping that all back. I soldered on a piggy back wire and ran it as neatly as I could;



Same at the manifold sensor end;


Cleared codes and am getting sensible temp readings and no CEL or fans;


Problem fixed, but I don't really want to leave that wire there permanently. If (when) I ever take the front off, it would give much better access to the loom.

No amount of wiggling or pulling the loom would give any continuity, so it must be a fracture on the cable or (more likely) the D121 joint. I cut back the insulation of the brown wire about 6 inches back form the G83 connector in case it had fractured near the crimp, but that was OK, so that's where I soldered my wire onto.

I'm pleased it's at least fixed for now.

 

[Howzat]

That's some stellar fault finding and documenting for future reference. Hats off to you mate.

 

[Loz]

I have found a couple of broken wires very close to the plugs, it might be worth using a pin to push through the insulation a few inches away from the plugs.

 

[catfood12]

I have found a couple of broken wires very close to the plugs, it might be worth using a pin to push through the insulation a few inches away from the plugs.

Cheers @Loz, I've seen that too before, where they break at the strain relief crimp on the terminal. I stripped back about 6" from the crimp terminal on the sensor, I could see the sensor but not back into the loom, so that's where I soldered my piggy back wire.

 

[Sanyes]

This is some serious documentation.
Unfortunately this is happening to me too.
My fan is kicking on when starting the van but after a few miles, the fan stops when the coolant temperature rises.
Swapped the temperature sensor first, thinking this was the problem but it turned out,it wasn't.
Now I have to do something similar what @catfood12 did in this thread

 

[Sanyes]

Thanks to @catfood12 documentation , I tested the continuity with the G71 manifold sensor but found out, that my brown wire had continuity but the red one, didn't.
So I started to check the wires behind G83, the coolant sensor and found the culprit.
The wires started to fracture/break, the red one was cut and the brown didn't had much until that one would break.
Don't know what could cause this type of wire fracture, maybe it was rubbing to something? Can't really tell.
So I soldered both wires just to be sure.
My faults disappeared and the sensor read the correct temperature.