[cb21rf]

I have a 2011 335d and have been getting the dreaded 4BF4 and the DPF warning light every time I start it up. BT Tool says it's been almost 1k kilometers since last regen, with soot mass at 22g.

I tried to drive it on the highway and try to get the revs up a bit so the temp will rise and regen will trigger, but have noticed something really odd with the coolant temp. When I drive it at higher revs on the highway, coolant temp actually seems to cool - it goes from about 89C to about 85-86C. When I idled it, coolant temp rose to 95C.

Tried manually forcing the regen through BT Tool but it's not working. I had my thermostat replaced a year and a half ago and I was wondering if this was probably the issue again.

I've had a couple of warranty repairs lately - active tank sensor and NOX sensors.

Any ideas or help on this would be greatly appreciated!

EDIT -- took it to an indy shop. DPF diff sensor is bad. They are also doing a DPF cleaning. Hopefully that does the trick.