Hi All, I am new here and was hoping that someone has had the same problems as I have with my MCS and would be able to point me in the right direction....

The 2011 MCS N18 has 79000KM on the clock and is in Limp Home Mode (reduced power) as soon as the car starts up. I have taken the car to a mini Dealer and the Fault Code is (pressure in high pressure fuel system below the required) the dealer advised that the high pressure fuel pump (HPFP) needs to be changed. I ordered a new HPFP from ebay and replaced the pump. I used a ELM OBD bluetooth scan tool with "Car scanner" app from play store, to read the faults and cleared the faults. however the car is still in Limp Home Mode. I used the scan tool to read any new codes and these are the codes it shows:

P3429
U0DA4
P3782
P2CO1

Checked out the codes on Google, but either cant be found or i get multiple different explanations for the same code.

 

Update:

I got the car to a BMW tech guy who was able to connect the MCS to a proper diagnostic tool.

The code that pops now, is P15A6, which is "Engine Oil pressure, Plausibility: Oil Pressure high before start.

So I start with check the connector plug at the Oil Pressure Sensor and found that the 5V power supply (Blue wire) to the sensor and the Signal wire (Yellow Wire) had a short circuit,

The engine oil-pressure sensor is connected with a 3-pin plug connector. The engine-management control unit supplies the unit with 5 volts and earth. The measurement range is 0.5 to 4.6 volts, which corresponds to oil pressures of 0.5 bar (50 kPa) to 10.5 bar (1050 kPa).

looks like the 5V supply voltage was being sent back to the DME, which interpreted that has high oil pressure.

So I managed to fix the connector, and the signal seams to be about right, Start up the car and its still in Limp Mode, not sure if its because I still need to erase the fault codes using the correct diagnostic tool. I tried removing the Battery terminal for 10Min and reconnecting, but still the car is in Limp Home Mode!!!

Will take the Car to the BMW Tech tomorrow, for him to erase the faults and see what else pops up now.

The next check will have to be the Oil control solenoid that's fitted to the Oil Pump. I dont think that its the issue as it would have throw a code if is was defective.

 

Update, I have replaced the Oil pressure sensor and I dont get the P15A6 code any longer, however now the MCS is throwing some new codes listed below. Also have the software and coding updated on the car, According the ISTA, most of the modules were on versions between 2010-2011, Now they are all on a 2017 version and I must say the engine sounds much smoother at Idle, the Rev Limiter was removed, passenger occupancy sensor is functioning again with no airbag warning light on the dash any longer, and i didnt change any hardware.

P2C57 - Charging pressure control, plausibility Pressure too low
P2BC1 - Mixture control: Fuel-air mixture too rich
P112E - Air mass system, plausibility: calculated air volumes in air intake system implausible

I suspect that P2BC1 / P112E code is a result of the low boost pressure and is not actually the O2 Sensor that measures the Air Fuel Mixture or the MAF sensor.

After doing some research on google, I found that the common problems related to Low Charge pressure, is a damaged Diverter Valve or a Waste gate flap not sealing completely. Going to start with the Diverter valve and then go from there, If its the waste gate flap, then I would have to replace the turbo

 

Thanks for your continued updates. I am reading as I have an 11 MCS also.

 

Thanks cargusjoh

Update, so yesterday, I picked up a Diverter Valve for the Turbo, I noticed that the design has been improved, unfortunately i forgot to take pictures. On inspection of the DV I removed, everything looked good, but I have read on this forum that guys had changed their DV although there were no physical damage and it sorted out their problem.

With High hope, I started up the MCS and BANG that limp home mode warning pops up.......Frustration is an understatement!!!

Code reader throws out a few codes, but the ones that stand out where

P2C86- Charging pressure - ambient pressure, comparison: Charging pressure too low
P28A1 - Air mass system, plausibility: calculated air masses in the air intake system not plausible


So the next this I did was remove the turbo Heat shield to inspect that the waste gate actuator is operating, and it was, Now I can rule out the Vacuum Pump, Vacuum Lines, Vacuum Tank and Vacuum Controller unit.

I still need to check id the waste gate flap is sealing, which I will check today. together with a continuity test of the wiring from the DME to the Charge Pressure Sensor and DME to the Intake Pressure sensor.

 

Update on the latest with the 2011 N18 MCS:

So I have dropped of the MCS with a turbo specialist, who have reconditioned the turbo, cleaned out the intercooler, boost pipes and remoived the Catalytic converter.

According to them there was a blockage in the intercooler, that was causing the problem with the car not picking up boost pressure.

So now the car is going into boost, but starts to misfire due to low fuel pressure in the high pressure fuel system!!!

So i pick the car up and drive it home keeping the RPM just below 3200, just before if starts to boost and about 2km from home i pushed the car up to 4000RPM and the car drove as if it was new......

So i took the car around the block a few times and it was back

I get home and im all excited, wait for the wife to come home, so we could take the car for a spin, and Boom its back in Limp mode due to low fuel pressure in the high pressure fuel system (P0087).

So back to square 1... plug the OBD scan tool and decide to drive the car for a while around the block to see whats happening.

Before startup, fuel line pressure was 5bar, coolant temp 31deg. no misfires, no stumbling, no stammering. Let it idle for 2-3 minutes from start, within which it dropped to a normal idle RPM on its own. Fuel pressure did not jump to normal range -- topped out mid 5.4bars. Test drive and it misfires as the car get into boost.
Drove around the block for a few more time then decided to pull off, shut it down, crank it up and gun it right after startup. Boom it was up to 102Bar, and when it dropped back it dropped to normal range (high 50Bar-55Bar). At this time it hit me that the Operating temperature of the car influenced what the HPFP was doing.

IN concussion when the car is below 98deg, the HPFP does not fo up more that 5.4bar, but as soonas the temp hits 102-106 deg the fuel pressure shoots up and the car runs normal.

Take note I did fit a new HPFP just before the MCS went in for the turbo work.

So the investigation goes on to find out how the temp effects the HPFP.

HELP, if you have had the same issue and have been able to fix the problem.