Hey everyone,
I have a common issue but a few questions that I couldn’t find the answer to:

Mazda 6 GY1, 05/2007, 121 hp, 140000km
I had DPF light flashing and engine in limp mode. Went to a Mazda workshop in Southern Germany, they changed oil and filter, found the EGR valve not working, cleaned it by ultrasonic bath, assembled everything and ran the forced DPF regeneration.
Car was running fine for 500 km on the highway. Then DPF light came on (constant on) while on the highway. Went off after ~10 minutes. Another 500 km later (90% highway) DPF flashing and engine in limp mode again.
Now my questions:
1. should the workshop have changed the oil after running forced regeneration instead of before? Or twice, given that it was bad already?
2. how’s your experience with using not a new but a cleaned EGR, is this a solution or is it only a temporary fix?
3. what can happen if I continue driving in limp mode? Okay, it’s not fun, less power and blinking lights. But does it harm the engine?
4. I’ve read about the DPF light reset procedure. Does this just switch the light off? Or does it remove the error and gets the car out of limp mode? Does it then run the regular automatic DPF regeneration afterwards again?
5. What about the injector calibration procedure? The workshop didn’t mention performing it, should they have done so?
6. which possible root causes are there for the DPF issue? So far, I’ve heard: EGR valve not working, possibly holes in a tube leading to air intake, pressure sensors not working correctly, DPF needs replacement, issues with the injectors. Any other suggestions?
7. above all is the question if there’s a definitive way to know that the DPF is still okay. It’s a very costly part, and I don’t want to replace it just to have the same problem again.

Let me know your thoughts,
cheers, Joachim