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Pete
Pete, Car Enthusiast
Category: UK Car
Satisfied Customers: 24697
Experience:  Over 17 years experience diagnosing and repairing automobiles.
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I have a 2008 L200 which throws a P1272 Code as soon as I

Customer Question

Hi PearlI have a 2008 L200 which throws a P1272 Code as soon as I crank it.I have tested the Fuel Pressure sensor with an Oscilloscope and a Delphi Diesel High Pressure Test Kit. Indeed it reads Fuel Pressure accurately.I have Load Tested the wiring from ECU to Suction Control Valve and Fuel Rail Pressure Sensor, the pins and female connectors are all clean and tight.I can clearly see that upon Cranking (Graphed Live Data) that Fuel Pressure Rises to 1650 - 1800 bar which I believe is excessive and sets the fault code.My thinking is that the SCV is not controlling the Fuel Pressure, I have replaced the SCV twice with no improvement.I am able to drive the SCV with my scan tool actuator function (Bosch KTS - Delphi DS150e and Snap on Verus)
JA: Sometimes things that you think will be really complicated end up being easy to fix with a Mitsubishi. The Mitsubishi Mechanic I'm going to connect you with knows all the tricks and shortcuts. Are you hoping to fix this yourself?
Customer: Further more
JA: Is there anything else the Mitsubishi Mechanic should be aware of about your Mitsubishi?
Customer: The SCV is driven by the ECU by a PWM / Duty Cycle With a NEgative on one Wire and a PWM Switched Positive on the Other.
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Mitsubishi Mechanic about your situation and then connect you two. I'll let you know when it is your turn.
Submitted: 10 months ago.
Category: UK Car
Customer: replied 10 months ago.
The SCV is driven by the ECU by a PWM / Duty Cycle With a NEgative on one Wire and a PWM Switched Positive on the Other.
I am able to control Fuel pressure manually using a PWM Generator connected to the SCV (Of Course I have isolated it from ECU) and I can control, raise and lower Fuel pressure as I wish. This tells me that the SCV fuel pumpare good, The Rail Pressure sensor I have already confirmed as good.I read from the 4D56 Manual that the Rail Pressure Limiter Valve will "Pop Off" at 2000bar and will then not close until the pressure drops down to 500bar.As I crank this engine I can see that Fuel Pressure rises to circa 1700 bar very Quickly (Im assuming that is setting the P1272 fault code) then when I rev the engine, FP (fuel pressure) rises to 2000bar, the valve pops off and pressure drops to 650 bar and sits there - The Valve has popped off at 2000 bar and then because it never drops below 500 bar (where the relief valve is designed to close again) the Rail pressure is now running uncontrolled.I am aware that the New SCV should be adapted to the ECU by Computer however I cannot get this Bitch (sorry) to start and idle without setting a fault , with the fault code set I cannot perform the "Learn" procedure for the new SCV.Be assured that the SCV is correctly fitted with the Gasket and O ring in Place.
Customer: replied 10 months ago.
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Expert:  Pete replied 10 months ago.

My name is ***** ***** I am a professional here at Just Answer. I noticed that your question had not received a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.My info is somewhat limited on your model here but I had seen no one else has responded and would like to see if I can help here.If at any time you feel that I cannot help with this please let me know.

It is possible that this is an issue due to a fault in the engine control module sending incorrect signals to monitor and control the fuel system.I have seen some of these fail before in the past needing replaced for faults like this here.I would have this checked into/tested further to see if this is the cause here and if found to be an issue it will need replaced for this fault.

If this was already checked or replaced let me know so we can continue.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete