EGR error codes P040D00 & P040C00 (temp. sensor)

[n10n]

Makes me wonder if this is the design to quickly warm up coolant entering into cabin heat exchanger....

Good point, although I would vote for just getting engine up to temp - quick coolant heat up is not necessary in summer

I didn't see the peak at the end

Now that you mention I probably (almost) idled for some time at the end of my sample drive as I went to fill her up but all the pumps were vacated.

now the positive/negative transition might have got the explanation.

I still don’t really grok this. Afaiu EGR coolant changeover valve and the actual EGR valve are separate, and I don’t see the point unless zero (off position) is somehow half open, and the neg/pos would be fully closed/open.

PS. Apologies @xcelrec for slightly deviating from your issue

Yes, apologies, completely my fault! Can’t help it when I see some interesting data and I do like open discussions around technical topics!

 

[xcelrec]

PS. Apologies @xcelrec for slightly deviating from your issue - but it's still about your sensor and how to take advantage of it

Yes, apologies, completely my fault! Can’t help it when I see some interesting data and I do like open discussions around technical topics!

Don't apologize! Even though I only understand half of what you guys are writing, its super interesting. So please, keep discussing here If you want !

 

[n10n]

Now I do see the behaviour also in my logs - haven't paid attention on that although tried to evaluate the EGR cooler blockage by recording everything related I could imagine.

View attachment 212102

I don’t as of now have any logs of IDE11872 but that indeed looks like exhaust temperature range, taken right off exhaust manifold.

I just looked at IDE07727 - coolant temperature at radiator outlet and it is <38° in my sample trip. I could not get how would it be possible to get 300° or so exhaust down to <50° in EGR cooler using coolant without some major pressure plays… but because radiator is so efficient I guess it just works out .

I will humbly cancel out my suspicions and agree IDE07729 measures air temperature.

 

[Aeroflyer]

Hello @xcelrec

I have what appears to be the exact same issue occurring on a 2017 T6 with CXHA engine.
My scan tool unhelpfully describes it as Temperature Sensor "A" circuit (same codes). So I am going to investigate the wiring and hope to find something like you did.

Looking at the sensor cable a bit closer, vw ran the sensor cable directly under some thin tubes. Guess the 150k km and vibration did the rest. The cable sheath was worn through and probably also the cable to a degree.

Do you happen to know where exactly the break/short was on the harness? It would save me a lot of hassle if I could head straight to the location of the problem.

Cheers in advance

 

[xcelrec]

Hello @xcelrec

I have what appears to be the exact same issue occurring on a 2017 T6 with CXHA engine.
My scan tool unhelpfully describes it as Temperature Sensor "A" circuit (same codes). So I am going to investigate the wiring and hope to find something like you did.

Do you happen to know where exactly the break/short was on the harness? It would save me a lot of hassle if I could head straight to the location of the problem.

Cheers in advance

Hej, yes.


In the picture (click to enlarge) the sensor cable is a bit pulled forward, but it's quite easy to access on top of the EGR cooler.

Maybe here it's a bit clearer, left sensor cable is the culprit.

 

[Aeroflyer]

Thanks for your reply.
So was it the wires from the sensor to the engine harness (so replacing the sensor fixed it) or actually on the main wiring harness where the break was?
Sorry for all the questions, but the sensor on mine was already replaced once.

 

[xcelrec]

It was the sensor cable. Replacing sensor fixed it for me (as you mentioned it comes with the wiring up to the connector), but I guess the issue could be anywhere in the signal chain.

 

[Aeroflyer]

Just an update from me. The replacement sensor had failed. It was a cheap one from Amazon (Frankberg brand) so hardly surprising but incredibly frustrating.
OE replacement fitted and all is good.

 

[Stu B]

Has anyone got a pic of where EGR Temperature Sensor "C" is
TIA