Check Engine Light On w/ P2789

the map and mass air flow sensor are combined on the prince engine and is held in by a small torx screw under the vvt motor on side of inlet manifold,
the rocker cover has a pcv valve in it when fails the idle will go all screwy etc and engine will get 02 sensor codes for reading faults etc, if the vvt ie variable valve lift ie on inlet cam shaft it allows the valves to open further controlled by the ecu on the car clever stuff this allows more air in to the cylinder so the map maf would be expecting a certain amount of air flow, but if the valves dont open correctly the air flow is limited and ecu sees it and throws a code, could try a powerlatch as per below , this resets it all and if software glitch will clear it , at least it rules out a glitch
How to reset all ecu's

this procedure is called a power latch

firstly turn on the ignition not engine running,IE FOB IN DASH SLOT, TOUCH BUTTON UNTIL SEE DASH LIGHTS ON IE FUEL GAUGES ETC THIS IS IGNITION ON, THEN FOR IGNITION OFF TOUCH BUTTON ONCE THIS SWITCHES THE IGNITION OFF IE SAME PROCESS HAS TURNING A KEY ON AND OFF FOR IGNITION, ADDED THIS AS WAS POINTED OUT TO ME SOME MAY NOT KNOW HOW THE IGNITION ON AND OFF WORKS FOR THIS, THE BODY CONTROL MODULE STAYS ON FOR 3 MINUTES ANYWAY SO THIS WOULD KEEP IT ALL LIVE ANYWAY TO DO RESET ETC,
open bonnet remove battery positive lead and then turn off ignition.
then touch the positive lead to earth,this powers down all ecus and resets erasing intermittent faults in the process.then reconnect the battery lead.
if the vehicle doesnt start straight away leave the ignition on for 2-3 mins as it has gone into anti scanning mode.

IMPORTANT PLEASE READ CAREFULLY
upon starting the vehicle DO NOT TOUCH THE THROTTLE allow vehicle to idle until cooling fans cut in to allow the engine ecu to reset correctly and reprogramme the learning curve,then drive in all gears upto 4,000 rpm accellerating steadily.

as stated this resets all ecus so any electrical faults caused by conflict errors in programming will be erased and fixed.if the fault is still evident there is a problem that will need further diagnosis

result that it seems like the wiring looms start to break down with age and heat have seen many over the years and on the psa Peugeot Citroen stuff as they share the engines the one that happens most is thermostat housing leaks seeps over time and the coolant soaks up the wiring loom and in to the under body BSM and rusts the pins out and get total shut downs and cant even read the ecu for a code etc, makes me wonder of they are using a biodegradable wiring that break down and black with age and heat etc, as most of this starts around the 7 years old mark, also the wiring when gets wet all the time and road salts get to the copper the copper turns green this green corrosion causes high resistances and effect the system that run on them, see this more on the maf and map and 02 sensors and thermostat and temp sensor circuits, in the uk for a 2008 mini clubman cooper d bmw want £505 for new wiring engine harness,