So............I bought my FL SD4 a few weeks ago and have been happy with it, pulls like a train and beautiful to drive. In the last week however it had developed a really annoying fault which manifests as follows: Car drives fine with no problems, stop car, re-start car and "Reduced engine performance" is triggered".

The fault code that is triggered is "B100A-15 (6C) Fuel pump authorisation - General electrical failure - circuit short to battery or open".
Now, the reduced performance will not re-set on it's own, I have to clear the fault code for this to happen after which the car is fine again............ until i next stop and start again. It doesn't happen every time, about one in three key starts.

I have read all the threads here on REP, have checked the intercooler hoses for leaks, the fuel filter is nearly new. I've run out of ideas! Please help!

I still have this problem. It seems that to trigger the fault I don't need to start the engine, switching on the ignition and letting the system do it's system check is enough. It seems to be annoyingly intermittent .

Anyone seen this before?

Sorry, never heard of this sort of fault. However bad earths and poor battery can throw all sorts of weird results. Do you have the additional earth strap fitted? If not, that is what I would do first.

Had the same fault since I bought the car a year ago but the it runs fine. I been trying to discover a cure.

An independant checked it out and told me that some cars throw the fault. They could have it in for a couple of days check it over but there is no guarantee it will be fixed. Just have to live with it until it makes the car undrivable.

In this case the fault triggers Reduced Engine Performance which i can only remove with my code reader so I'll have to find a solution. I've ordered a second earth strap and ill try that first as suggested. Thanks for your advice.

Sorted. It was a faulty DPF pressure sensor. Diagnosed by analysing live data from the sensor.

Well done but are you still pulling the B100A-15 (6C) Fuel pump authorisation - General electrical failure - circuit short to battery or open Error Code

Just checked and yes, the same fault code now keeps returning even though the car is now fixed and driving fine.

Thanks for the reply. It's as I suspected.