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Lou P.
Lou P., ASE Certified Technician
Category: Porsche
Satisfied Customers: 4064
Experience:  I Have knowledge in almost all car lines and can help with general questions and more!!!!!
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2008 CAYENNE FAULT P12A2 = CHECK PRESSURE READING = MOST OF

Customer Question

2008 CAYENNE FAULT P12A2 = CHECK PRESSURE READING = MOST OF TIME AT 35160 MBAR = HEAVY ACCEL WENT TO 10000 MBAR FOR SPLIT SEC. SEEMS WITH IN RANGE
Submitted: 1 month ago.
Category: Porsche
Customer: replied 1 month ago.
ANY THOUGHTS ?
Expert:  Jim replied 1 month ago.

The following checks are needed to isolate this problem.

Check for excessive vacuum in the crankcase. The crankcase pressure regulating valve is apart of the cyclone oil separator on this engine. This assembly is built into the cylinder head cover.

Remove the vacuum supply hose running from the intake to the housing. If the vacuum in the crankcase goes away, the issue is with the crankcase pressure regulating valve.

The entire unit is replaced as a whole.

Issues with the crankcase pressure regulating valve and the breather system can cause a multitude of performance issues.

If this information is helpful, please accept my answer and leave a positive rating before leaving the site.

Customer: replied 1 month ago.
IF U REMOVE VACUUM HOSE = VACUUM WILL GO AWAY = ITS THE WAY IT GETS VACUUM ? . ENG. DIES WHEN THATB IS REMOVED ? R/R OIL CAP AND HAS VACUUM . SEEMS LIKE A LOT . MAY NEED TO PUT ON A SLACK TUBE TO C INCHS OF VACUUM ?
Expert:  Jim replied 1 month ago.

The engine may die when you remove the hose because of the leak.

Customer: replied 1 month ago.
TIME BEFORE U CAN CALL ?
Expert:  Lou P. replied 1 month ago.

Hello, different tech here, Lou , what engine do you have in your Cayenne?

Expert:  Lou P. replied 1 month ago.

P12A2 Diagnostic information - DME V6 DFI Fuel high pressure implausible NOTE: The diagnostics detect a deviation in the fuel high pressure. Diagnostic conditions - Battery positive voltage 10 V ... 16 V - Engine start detected > 5 sec. - No fault codes P0193 or P0192 Possible fault causes - Tank vent (TEV) mechanically faulty (does not close fully) - Fuel high-pressure sensor faulty - Fluctuating fuel high pressure, e.g. due to: ***** ***** fuel circuit - Pressure relief valve - Fuel high-pressure pump - Injection valve

P12A2 Diagnosis information - DME V8 DFI Fuel high-pressure sensor implausible NOTE: - Faults in the fuel high-pressure injection area are often caused by defects in the predelivery circuit (fuel low-pressure). - Therefore, if there are problems in the fuel high-pressure injection area, the predelivery circuit must be checked first. NOTE: Diagnosis detects a permanent deviation of the measured fuel high pressure from the calculated fuel high pressure. The fuel high pressure value is calculated from various variables such as lambda control and fuel quantity control. Diagnostic conditions - Battery positive voltage > 9 V - Engine start recognized > 250 sec. - Engine temperature - 10 °C ...+ 100 °C (50 °F ... 212 °F) - Engine speed 450 ... 4,000 rpm - Lambda control active Possible fault causes - Predelivery quantity or pressure in fuel low-pressure circuit too low - Fuel high-pressure system leaking - Fuel high-pressure sensor faulty - Fuel high-pressure pump faulty

the fuel pressure will need checked from the low pressure in tank pump.

Customer: replied 1 month ago.
WAITING FOR A REPLY ?
Expert:  Lou P. replied 1 month ago.

did you not see the code info i just sent??

Customer: replied 1 month ago.
HI LOU = YA GENERIC STUFF . SAW ALL THAT ON ALLDATA = MY QUSESTION TO U WILL LOW OUT PUT FROM ONE OF TANK PUMPS CAUSE A HIGH PRESSURE FAULT IN HIGH PRESSURE SYSTEM ? SYSTEM IS RUNNING AROUND SPECS AT 35000 MBAR AND UNDER FULL LOAD PEAKED ONCE FOR A SEC. AT 10000 MBAR . TRIED NEW SENSOR = SAME READINGS = EASY TO TRY . INSTALLED A HIGH PRESSURE PUMP LITTLE OVER A YEAR AGO AND NO PROB. SINCE . SHE RAN OUT OF GAS LAST MONTH AND SEEMS TO HAVBE STARTED AFTER THAT . BUT HIGH PRESSURE FAULT FROM LOW PRESSURE FROM TANKS ?? WONDERING .
Customer: replied 1 month ago.
DEALERSHIP U R AT ? I WORKED FOR PORSCHE 1980-90. SF AND SANTA ROSA
Expert:  Lou P. replied 1 month ago.

yes sir, in these models the first failure is always the high pressure pump, since its somewhat new , its not likely the issues, it most likely going to be one of the two tank pumps, and peoria IL, about 10 years mostly mercedes but porsche silver for about 5 years.

Customer: replied 1 month ago.
YUC HATE MERCEDES = BMW FOR 28 YRS NOW
Expert:  Lou P. replied 1 month ago.

lol, same for me and bmw, i think its a love hate, they do things differently, benz are super easy to work on, im sure you feel the same about bmw,

let me know what you find and if you need more info, sounds like you got a good head on your shoulders, but the fault is going to be one of the pumps, either low pressure or high, Lou P.

Please take a second and click the stars at the top of the screen to rate me so i may receive my credit , 5 stars is ideal , please request me in the future.
Keep in mind then when you rate it does not end our conversation. you can still return here to me for follow up information if needed, Lou P.

Expert:  Lou P. replied 1 month ago.

you will get the high pressure fault from the low pressure circuit because the pumps cannot keep up with the demand of the fuel quantity. so anytime we have a issue with the high pressure system in the gas and diesels we always always check the low pressure side first, both for pressure and flow.

Customer: replied 1 month ago.
FIRST TIME ON THIS THING = HOW DO I GET U IN FUTURE FOR MERCEDES = I WORK ON ALOT OF THEM AND ON NEW PORSCHES .
Expert:  Lou P. replied 1 month ago.

ok so best way is to return to this chat and click on my picture or the link that says ask Lou another question, or google JustAnswer/Lou P and you will see hundreds of thousands of my chats, click on anyone and you can ask me a question from there, or anytime you are in the mercedes section and ask a question in the first line always put 'ATTN LOU P ONLY' and the other techs should leave it alone for me, after a few questions you will have your favorite techs at hand and the process down :)

Expert:  Lou P. replied 1 month ago.

I have to leave to commute, so i will check back later when i can today, if not please let me know the outcome and do not forget to rate my service please, we are only paid if we are rated positively and 5 stars is always preferred :)

Expert:  Lou P. replied 1 month ago.

did you make any progress?