G448 Sensor: constantly 222*C, plugged in or not

Vappy

Registered User
As the title says, my G448 sensor reading on my app says it is 222*c all the time, whether the new sensor is plugged in or not. I checked the wiring going into the ECU and it's like new, with no evidence of water damage or tampering.

This tells me that somewhere along the wiring for the sensor, there is some resistance due to a dodgy wire or even dodgy socket for the sensor to plug into.

If my understanding is correct, it's a 5V line with a small resistor on the ECU/PCM, and then resistance on the sensor gives an accurate temperature setting.

What do you guys recommend I do next? I can check things like continuity, resistance, voltage, etc with a device, but I think that the stuck reading explains more of a wiring issue from A to B?

Thanks

EDIT: Car is a 2007 3.0TDI CAPA engine.
 

Vappy

Registered User
A bump and an update on the situation. I double checked the wiring at both ends and don't see any damage, which opens up the question as to whether any software tampering has been done. That's way past my capability, and I only have an ELM adaptor to see basic readings.

I have bought some contact cleaner to give the socket the sensor plugs into a spray, let it dry and see if that clears up any potential issue within the socket itself. It does look a little dirty I suppose. Other wise, i'm out of ideas.

EDIT: Contact cleaner didn't help at all.
 
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desertstorm

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I suspect that the app you are using to look at the value is not correct. I have a CAPA engine and tried using Torque to monitor some stuff on the car and it does the basic stuff like RPM, temperature etc but sensor values either don't display or are incorrect. If you have a multimeter measure the resistance of the sensor. They are not thermo couples these days they use platinum RTD sensors so basically like a thermistor but good for 1000 degrees C.
I presume you have a fault code for that sensor. Measure the resistance of one of the other EGT sensors, and quite often the connectors are the same on the various sensors so you can plug one of the other sensors into the G448 and see if the fault code clears.
 

Vappy

Registered User
Thanks for the reply, desert.

I currently have no fault code for it, but the last time it did a DPF regen was almost 50,000km ago according to the app I use, which was even before I owned it, and consequently haven't ever experienced a DPF regen in this car. My MIL isn't on and I have no DTCs, but seeing that it hasn't done a regen in forever and that eventually will lead to a MIL, I started these investigations.

P.S. The app I use is called Car Scanner and is the one reporting 222c, which also shows normal temperatures for the other EGT sensors. When I unplug any of the others, it reads 1000c instantly, so I will do some hot swapping of sensors to see what reading comes up, and also check the resistance.
 

desertstorm

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It's possible it's had the DPF gutted. Easy to tell, if there is any kind of soot in the tailpipe it has no DPF.
I cut open the rear boxes on my car at around 80K miles and you could eat your dinner of the inside of the rear box.
IMG_1497.JPG
 

Vappy

Registered User
Hmm, it does have quite a bit of soot in the tail pipe - exactly the same looking stuff I saw on the end of the EGT sensor when I took it out. The thing is, it doesn't sound anything remotely close to what i've heard online with DPFs removed and no back boxes. I've had my back boxes off in the past and it's sounded no different. I've never seen the temperatures get that high on the EGT readings, which could support it not having any innerds?

Family members have said it's a loud car, but it sounds stock when I compare it to stock audio samples..

I appreciate your help on this matter, desert. I've learned a lot from your posts and threads from the past!
 

Vappy

Registered User
That would make sense. The soot mass measured and calculated has never changed from 59.8g, ash volume measures zero. If it is indeed gutted, I am quite taken back by simply how quiet it is. It really does sound bone stock - I feel like i've been blessed with no DPF problems and robbed of a good V6 note, haha. You can't have everything.

I think i'll just leave the G448 alone and make cleaning out the intake my next job for when the weather is warmer.

Thank you for the help, desert!
 
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