NigelBywater

Did a little digging and found the official manual. Seems like 1 is underneath.

Thanks for this. That said, I have no idea where sensor 1 is under the bonnet based on this. As I said, 2 and 3 are easy to find but 1 is illusive when I look at the engine bay.

Thanks Steve. So I’ve located 2 and 3, uncoupled each of these to determine which was which. Where 3 and 4 are is anyone’s guess. I’ll take a look at you previous contributions for the layout of the sensors.

Thanks Stevey, for this. Bought a replacement pressure sensor. Ash load is consistent with age and not an issue right now. This really leaves the sensor as the culprit. No smoke 💨 being released so that rules out oil and coolant and the EGR is working fine. Anyone know where the sensor 1 is? 2 and 3 are easy to spot.

My Audi A6 Ultra has been trying to regen for weeks now P2458. Ends up putting me in limp mode continuously. All tests say the DPF isn’t blocked. Strange thing is the discrepancy between regen temperatures on the motorway where sensor 1 (post turbo) is 230ish degrees but sensors 2,3 and 4 reach over 550 and up to 620 degrees. Still won’t reset even when I drive it like I stole it. Is this a sensor 1 issue?

I’m having issues locating Sensor 1. I get the error P2458 but the car won’t regen. I got the readings last night at 2500RPM: My pattern: • Sensor 1: 247 °C • Sensor 2: 541 °C • Sensor 3: 615 °C • Sensor 4: 508 °C This surly cannot be real gas behaviour; gas cannot more than double in temperature between sensor 1 and sensor 2 without an enormous heat source in between, and certainly not while still under the same exhaust flow. I assume therefore that sensor 1 is telling the ECU not to begin a regen. I’d welcome help locating this sensor.