Very strange warning light and engine issue

[jonwatt]

I'll be amazed if anyone know this but here goes. A4 B8 2.0TDi

Some time ago my SPF warning light came on with the engine light and the coil light, the car immediately went into limp mode.

Took it to my normal garage guy, he said I could either replace the DPF or get it cleaned. Got it cleaned, no change. Went back to the cleaning company, they did a load of diagnostics, said the DPF was spotless, cleaned it again and flows both sides were well within tolerance, it should be running fine. On the way home, filled up with fuel, drove out of the garage, coil light goes out, engine returns to full power. A bit later the DPF light goes out but the engine light stays on. Now, if I ever get another warning light on the dash say for low fuel or low washer fluid, the DPF light comes on and if left long enough will go back into limp mode. Topping up the fluid or fuel will bring everything back inline and working although the engine warning light always stays on.


Any ideas? My local garage guy doesn't know. I took it to an electrical specialist who just said the DPF needed replacing.

[DanSkoda]

Has the dpf pressure sensor been replaced? Not an uncommon failing on them. As for the levels influencing things I've not heard of before!

[msremmert]

Don't suppose you have any friends with a vagcom who could kindly check the code for you once the light is on?

Dfp pressure is a common failure (as above) and if it's failed the car won't be regenning.

A friend of mines failed and then he had a lend of my vagcom to recalibrate the replaced sensor. To my knowledge the car is still OK!

[bearman68]

As above, the sensor will need recalibrating, and the DPF will need a forced regen from a more sophisticated unit than Vagcom. I know it shouldn't, as it's clean, but you will need to drive it with the diagnostic kit attached, to perform a regen. (or cut it out and remap)