New owner! Big problems.....

[Badsmerf]

Wouldn't the engine running that low cause a bunch of fuel to be burned and hydrocarbons into the exhaust? I didn't have ista set up when I went into limp mode unfortunately.

That is the right part right? Can someone also explain how to delete these codes individually?

[Thecastle]

Originally Posted by Badsmerf

Wouldn't the engine running that low cause a bunch of fuel to be burned and hydrocarbons into the exhaust? I didn't have ista set up when I went into limp mode unfortunately.

That is the right part right? Can someone also explain how to delete these codes individually?

So injecting fuel into the exhaust is done on purpose in these engines. The cars do post injection events (inject fuel when exhaust valves are open) to send unburned fuel into the exhaust where its is burned by the Diesel Oxidation Catalyst (DOC). The point of the unburned fuel in the exhaust is so combustion takes place in the exhaust stream raising exhaust gas temperatures high enough to burn the soot captured in the DPF. So by design these cars are intended to operate with unburned fuel in the exhaust as part of their normal operating process.

The DOC and DPF ensure that minimal residual fuel and soot are left in the exhaust by the time the exhaust stream reaches the SCR. The SCR doesn't have an issue with unburned fuel per say its bigger problem is having its passages clogged by soot, which is why its located post DPF. Also it can't handle sulphur either.

BTW if the DOC wasn't working on your car you would have bad diesel stink exhaust fumes, like making your eyes water bad. So all of this was a long way to say, I don't know why your SCR failed, but low engine temps don't kill them as far as I've seen. They kill DPFs (don't get hot enough to regen), glow plugs and fuel economy (engine doesn't leave warm up mode). My car has had its SCR injector, Catalyst, and DEF tank all replaced at separate times and has not had the thermostat fail. SCR failures are not uncommon on BMW diesels.