P109B Fault code

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Active Member
Jul 3, 2014
Holbury, Hampshire
E350d, E350 CDI sold on at 357,000 miles, C270 is sadly no longer with us, chewed a glow plug :-(
Hi All,
I'm getting a P109B fault code, I have searched but can't find anything conclusive. The car is running cooler than normal, fluctuating between 60 and 80 degrees and doing lots of DPF regens. Seems to be driving ok though, any ideas what may be wrong?
I did put some DPF cleaning additive in the tank prior to removing and cleaning it but ran it down to about a 6th of a tank then filled to the brim so would be surprised if this is still having an effect causing the regens?
Sounds like new thermostat time to start with ?
Very rough idle and lots of smoke when started a while ago, settled down when warmed up a little though 🤔

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