Hi, I've got an X3 (2.0 Diesel 2007) which was stuck in limp mode (DPF Backlog + glowplug change required.) Yesterday I changed the plugs and took it out for a drive to force a regen which i think was successful. Parked it up, reset the codes and then drove around for 5 minutes - Checked codes again and nothing was showing and the car felt keener to accelerate with no obvious restrictions. Went out this morning to take it for a quick run on the motorway to check we were actually out of limp mode and the car ran OK however i noticed the OBC had reset (No mpg recorded/clock was set to --.-- etc) however the service interval info remained and A/C, radio etc all functioning correctly. The code reader will also no longer connect (Although connected fine when the car was parked up last night). Took it for a test drive, 15 miles on surface roads and a quick run on the motorway and it's running fine and not in limp mode, however when i turned everything off and back on again the OBC once again reset. - I've checked the (+) battery cable which runs from the drivers side to the nest of cables next to (What I, as an inexperienced monkey) believe to be the ECU and this has continuity and is securely connected. This is the only battery terminals i disconnected (Not sure if this is where i went wrong and should have disconnected in the boot too?) - I've also checked all connectors which where moved/unplugged to do the glow plug changes and this was all OK too. - As a "grasping at straws" effort I've also tried resetting the OBC via the test functons but this made no difference. The only tell tale sign I can find is when turning to the second ignition point there is a loud repetitive clicking (Like a relay firing or a pump?) and the dials appear to drop (Excessive battery drain?) momentarily. Once this stops the vehicle starts and drives fine. The clicking seems to be from something in the cabin, rather than the engine bay (It is louder in the cabin than the bay) I've uploaded a video below:
The glow plug control unit was changed a week ago (This was prior to limp mode, it went into limp mode after this was installed - Garage blamed DPF/Plugs and refused to work on it for another week and half, hence me trying to get it running) the vehicle was driving fine prior to this (But with heavier than expected fuel usage) Any pointers on where to go next would be greatly appreciated.