Low rail pressure prevents the E90 N47 crank from starting.

[Black_raven]

I started this thread since the problem is driving me crazy; I had already contributed it to another one, but it's probably too long now. If I am unable to locate the problem tomorrow, I will have to arrange for the car to be repaired at a garage.

While returning from Heathrow, the vehicle abruptly stopped responding (the "drive moderately" sign flashed on the dashboard) and would not turn over. I managed to get my car towed home, but they were unable to back into our driveway, leaving it parked on the street. Unfortunately, I do not have a secure method to get underneath it. In addition, it restricts my activities during rainstorms.


Just before Christmas, I took my car in for the B+ and blower wire recalls. I had been putting them off because I didn't see any problems with the wiring and was afraid they could mess with anything and cause a problem. It looks like they have, but I still don't think that's the problem with my crank not starting.

I've done my best to summarise everything that has transpired with the car since the beginning of December.

Current Tasks
16th December: Vehicle brought to Marshall BMW for recall repairs (airbag, B+ cable, and blower cable rework). Returns a number of S-codes for use with the control unit, siren, electronic fuel pump, roof function center, CID, alarm, and electronic fuel pump. I still haven't found out what caused it. The codes that tend to appear most frequently are:

There is no communication with the electronic fuel pump module (S 0098), the CAS (S 0074), and S 0114. No communication with the control unit, air conditioning, navigation system, or JBE (S0117, S0155, and S0212, respectively).

On occasion, the option to remove codes becomes greyed out and cannot be chosen. Similarly, accessing the ECU functionalities is not always possible.
19th December: Undersealed rear subframe, front control arms/links/wishbones, gearbox fluid and brake fluid were replaced. Noticed an oil leak on the cover of the rocker.
January 18th: Installed new copper washers, cleaned injector seats, and replaced rocker cover and gaskets.
On February 5th, while driving home from Heathrow Airport, my car broke down about 5 miles from my house. The Check Engine warning light momentarily came on before the car shut down, and now it won't turn over, even though it cranks normally. Except for the codes that are present after recall, no other codes are used. Although the pre-supply pressure rises to 3.9 bar, the main rail pressure remains at 10 bar. Over the rocker cover, sooting was noticed. It was found that the hose connecting the exhaust back pressure sensor was not properly reinstalled following the change of the rocker cover. Working without producing any output. Viewed codes again following cranking, and 04B90 was detected.
The lift pump, HP fuel pump, metering valve, pressure accumulator, rail pressure sensor, and rail pressure relief valve were all replaced from February 12th to the 17th with used but billed as "working" equipment.
Got the codes cleared and tried to access the fuel system bleed procedure, but couldn't get in touch with DDE.
The option to do a fuel system bleed was unavailable when I finally gained entry to the DDE menu.
The lift pump may be powered for two minutes using the spare battery.
We saw and cleared multiple communications-related codes.
Car continues to spin, but won't start. During continuous cranking, the rail pressure can spike to as high as 70 to 90 bar, which causes the engine to try to start but fail.
While cranking, the central display may show many codes and messages, which could be caused by a depletion on the battery.
After removing the DDE make contact relay, a fused jumper was inserted across terminals 2 to 6. It appears that accessing DDE communications is still not possible. Error code for DDE relay recorded. The car turns over, but it doesn't start since the rail pressure isn't there.
There is no indication of injector leakage while cranking, according to the leak off check.
While cranking, the rail return hose became twisted, yet the rail pressure remained unchanged.
I turned it on after disconnecting the rail return hose. When cranking, fuel leaks out of the return hole of the pressure rail.
Relay for making contact was replaced. The fuel bleed process cannot proceed because ISTA cannot communicate, although the DDE is now showing as green.
Transferred HP line from HPFP to rail and kept an eye on flow rate as cranking was done. Looks like the flow won't be able to develop pressure and is moving slowly.
february 20th and 21stSwapped the HP FP for a refurbished one. Examined the engine bay for any signs of fuel line leaks. The pump was powered for two minutes by a battery. I managed to complete the first part of the fuel system bleed procedure (pump operates for three minutes), but unfortunately, I was unable to proceed to the second part since the car refused to start.
There have been no increases since pre-supply was at 4.1 bar and rail was at 10 bar. After re-cranking, the rail return line became clogged, but the rail pressure remained unchanged.
Taken the DDE off and checked it for rust and water damage; everything seems OK.
I measured the voltage drop across the splice in the B+ cable while cranking, and it was 0.01V.
Checked at 60 ohms at the PT-CAN on the OBD (pins 6–14).
Revise (to include): I swapped out the JBE to make sure the module isn't the source of the communications problems.
Revoked the pressure rail regulator adjustments after an unsuccessful attempt to reset them, according to ISTA.
During a test drive, the engine was turned on but the clutch was not depressed. The pump activated and the central display indicated a pump failure, even though the engine was still running. The driver maintained a moderate speed. The display notice was cleared, but the pump did not restart, even after cycling the ignition.

Since there is still one component of the system that needs replacing, an EKPS is on its way to me.

[paulh2602601]

A malfunctioning DDE that is unable to regulate the HPFP metering valve is the only remaining possible explanation.
You have already replaced the fuel-related components (I wouldn't put my faith in EKP to fix it) and the HPFP twice, yet it continues to not produce any pressure even after mechanically twisting it.

[Black_raven]

I appreciate that, but for now it's more of a hit-and-miss than a strategy for success.

After I found the K-CAN wiring diagrams, I was planning to inspect the bus to determine whether the CAS was causing it to be dragged down and, consequently, the communication codes. Whether the CAS could intervene with the DDE to halt the pressure buildup was something I pondered. Upon matching immobiliser codes, my understanding is that the CAS sends the start enable signal to the DDE; however, I am unsure of the symptoms.


I was wondering if it would be best to simply get a full set of CAS, DDE, lock, and key in order to verify the fault has been resolved, before sending both modules for cloning, so that I can preserve the VIN, mileage, etc. Another option is to simply obtain the DDE and replicate it. Time is of the essence; I need the automobile by next week's end; hence, I may have to settle for purchasing the set and cloning it when I have more time.

By the way, have you heard anything about the possibility of reducing the donor's mileage? Like I mentioned before, I'd like to maintain accurate mileage records, and I'm worried that I won't be able to adjust the settings from a higher-mileage vehicle to my lower-mileage one if I borrow a set.

[paulh2602601]

When my f11 started loosing voltage at the terminals a few years ago, I thought it might be a cas problem. As a result, the sensor voltage codes were all low, and the crank wouldn't start. By connecting multiple power sources to the DDE via the JBE module, the CAS enables starting after the immobiliser is checked.
Although I am not sure, I would think that there would be codes that indicate CAS has dropped.


It could be wise to prepare the circuit diagrams and verify the terminal voltages of the power supply from CAS and JBE before proceeding with the control unit replacement and cloning.

People with the right software can fix mileage issues if you do need to replace pieces.

[Black_raven]

Please tell me that the lock does not contain any coding information in the event that I decide to proceed with the CAS/DDE swap out/clone method. Thank you. Instead of changing the locks on the doors and glovebox, I could just use the manual blade key and insert it into the donor set's keychain.

[paulh2602601]

Changing blades is a simple task.
It is not necessary to change keys when cloning CAS. I sent both the original and replacement CAS off, and they simply copied the data over.
After cloning, DDE, I thought it would be as easy as plugging it in.

[Black_raven]

Unfortunately, I did not have much time to investigate the problems today. I was given forty minutes. Very strangely, I spent the majority of that time attempting to identify continuity on K-CAN [Green and Orange Green twisted pairs], yet all of my attempts appeared to be open circuit. Finally, I went ahead and purchased a set of four things on eBay: CAS, DDE, Key, and Instruments. Expected arrival dates are Wednesday through Friday. I will attempt additional continuity checks when I have the time, but this week is really hectic. No visible indicators of damage were found when checking the CAS. I removed the screws from the DDE, but I was unable to remove the cover. Fearing harm, I replaced the screws.

After cloning, it should function properly since DDE solely relies on the CAS for handshake and start enabling signals. I was wondering if anyone might suggest a cloning company.

[paulh2602601]

I had never had DDE done before, but I merely saw an ad for it on eBay when I had CAS copied.