Hi all,

My Panamera (2011 make) is letting me down lately.

The 'reduced engine power' is popping up often lately + the engine is starting rough (takes some time to start, but always starts so far). Restarting the car helps in getting rid of the message.

Sometimes no message is being displayed, but still the engine is holding back...mostly in 4th and 5th gear. Again, restarting helps getting rid of this.

Went to a local garage. They hooked up the computer and indicated an issue with the high pressure fuel system. Changed the sensor, but unfortunately the issue is still there and also when checking the computer after sensor replacement...same message about the high pressure fuel system.

According to them the pump itself was visibly in new state and not leaking or whatsoever. Unfortunately, they could not test the pump to make sure whether the pump is the rootcause or not.

The dillema is now to pinpoint whether the HPFP is indeed the rootcause. Replacing the pump is quite expensive. The pump itself already costs 1000 EUR.

Hope someone here can help me out.

How can I make sure the pump is indeed faulted en not something else (plugs, injector, etc.)?

Thanks in advance!

 

First step = get a diagnostic tool. I opted for durametric which, while ahead of the pack compared to other options, is still (at least I have been told) a distant second to the bootleg porsche software/laptop combo for somewhere around $700. I regret not doing this but the durametric has helped quite a bit in narrowing in on some issues. I think a lot of people with earlier panamera turbos, myself included, have similar symptoms (PASM/reduced power/misfiring etc) that all stem from at least one but likely a combo of several common root causes - plugs/coils/o2 sensor/old battery/MAF or sensor issue etc.

my 2011 panamera turbo is my first porsche - compared to other german cars I have owned (Audi A6, SL65 AMG) + american cars (a few vettes and a 2004 Viper that has managed to survive) + various-not-worth-mentioning hondas - I am seeing that while the panamera seems to have been built well, what would be small electrical weaknesses/inconveniences on my other cars seem to set off chain reactions or put the car into limp mode to the point where they need to be addressed else the car be non-driveable.

Get a scan tool, start researching problems online and educate yourself as much as possible (I am only starting this myself) because for these cars, stealerships and "cheaper" indys will happily bend you over in parts/labor if you dont know the details and cost of the issue you are seeking to remediate. I found this out the hard way.

Could it be the HPFP? perhaps. But your going to feel like an idiot if you go through the process of addressing only to have the problem persist and have it turn out being something stupid like an cracked coil or an old battery - good luck!

 

Thanks for your reply and advice!

 

I just ordered a Foxwell NT510elite. Even with codes sometimes it is hard, but it is better if you got the actual codes that the car put out. The car was at the dealer for a recall and had a check engine light the day before the appointment. Although I cleared the codes I gave them to the service advisor. They sent the car home running smooth but a week later things came back and progressed to even worse.

Did the shop test the low pressure fuel pumps? There is a pressure test procedure and a volume /quantity test procedure. It's in the service literature that if you suspect the HPFP first test the low pressure fuel pumps. Try to find out the actual codes...

 

I had the engine fault, as well as chassis fault, PDK fault, etc (5 lights of death lol). But I also had a check engine light for a throttle position sensor. It was a bad throttle body

 

Hey JTM Holland - I have a Panamera 2010 4S with the exact same problem. When I leave the car parked for several hours, I turn the ignition key, and it takes ~5-7 seconds to actually start and it sounds like not enough fuel is going through the engine. I think the cold weather makes it worse. Once it starts, the Reduced Engine Power lights up and engine runs somewhat weak (sometimes this light doesn't come out - but lately more so, especially as the weather gets colder). Then after a minute, I turn the engine off, turn the ignition back on, and it works perfectly fine. I connected the iCarSoft POR II, and it gives me a P1031 code (Fuel High-Pressure Sensor Stuck At Start) and P1023 (Fuel Pressure/Quantity Too Low At Start). I took it to an Indy (who I trust) and said "I can tell you the possible problems but I do not have the experience to fix your car" He told me that the following are NOT the problem: the battery, the coils, the spark plugs, the High Pressure Fuel Pump (if broken, then the car wouldn't run smoothly after re-starting the car) or the starter (if broken, the car wouldn't start at all). What he suspected was that the fuel pressure was leaking somewhere and redirecting fuel back to the gas tank when parked for a long time (which makes sense as to (i) why the engine takes longer to start, since there is no fuel in whatever pump and (ii) why the car starts fine when turning it off and immediately turning it back on, since there is fuel in the whatever pump). He also said could be a sensor. But ultimately, he didn't want to spend countless hours disassembling the car, swapping parts, and charging me a small fortune for something he might or might not be able to fix. So he told me to take it to the Porsche Dealership as they would be able to diagnose the problem more precisely.

I have spent so much time researching this issue and the thought of taking it to Porsche is driving me nuts. That said, I was very curious what ultimately happened with your car and if you were able to fix the problem. If so, would you mind sharing?

Thx!

 

Hey syh244 - my Panamera 2010 4S is at a Porsche Specialist at this very moment, with similar problems as yours. His first (quick) diagnose is that the HPFP is not functioning well. How did your story finally end?
Thanks,
Richard

 

My symptoms are the same as @syh244Durametric shows same P1023 (Fuel Pressure Reg valve short upper limit) and P1031 (IMRC valve N316 upper limit). This has been intermittent for maybe a year/10K and not getting worse or better. My excellent porsche indy says P1031 IMRC is not important but P1023 might be HPFP. Before a long road trip he checked with PIWIS over multiple days and said he'd never seen an HPFP going bad that didn't show some pressure issues, and mine was perfect. 5K miles later, still the same: reduced power (and start-stop disabled) at 10-20% of starts, clears with restart. Maybe worse if it sits for a week, maybe worse colder, maybe worse at altitude. The car runs like crap if you don't clear the reduced engine power error, but I don't think there is any performance issue after I restart and clear the error. VERY interested what syh244 or JTMHolland figure out. I can't get motivated to shotgun $1800 for HPFP or a lot more if I let the dealer at it. Thanks.

 

Have you tried during the key start process leaving the key in "Run" for a few seconds prior to moving on to "Start"?

The purpose of this delay is to allow the low pressure lift pump time to pressure the system.

I let my car sit for 3 months without starting over this past winter and noticed that the lift pump ran for several seconds to re-pressurize the system prior to the first time I went to start. Only time it has noticeably run the LP fuel pump prior to starting. No issues -- jut heard the pump running.

Might be a way to troubleshoot the issue between a LP lift pump and HP fuel pump problem. Could be the system pressure is leaking down while car is off.

 

Chuck, two variables I have tried are: 1)waiting a few seconds between run and start as you suggest, and, 2)holding the key on start until it starts instead of releasing it and letting it auto-start. I have seen the “reduced power” fail with both. I am pretty sure 2) helps, but have not tried 1) many times. I’ll change my regular start to doing both and collect data.

In a fit of data collection, I hung a scope on the power posts under the hood. Picture 1 is a warm start – under 1 second (10V is center line). Picture 2 is a long cold start that did not get "reduced power" fail – lots of cranks and 2.4 secs. That seems longer than it used to be. Picture 3 is a cold start that took 1.7 secs and had the “reduced power” fail. No idea what it could mean.

I loved my 41C, but loved my 34C best.

1) Warm Start - no fail


2) Long cold start - no fail.


3)Cold start - FAIL (reduced power)

 

Looking at your pre-start voltages on the scope ---- seem a little low for an AGM fully charged battery (should be 12.8-12.9 or so).
Any chance you have a battery capacity issue? These cars are VERY sensitive to voltage issues - car will throw lots of strange codes / symptoms that are cleared up by replacing battery.

If you have access to a good battery tester, might be worth a quick check.

I had an HP34C as well (made it though 3 semesters of physics with it) --- moved up to the 41 when I got into the higher level engineering classes - needed more programming space & ability.

 

Chuck, I’m not sure the scope vertical adjusts are perfect, and the traces were taken at different times. So I took DVM readings at the power posts under the hood.
1)car off overnight, light background load: 12.77V
2)open door, more stuff comes on: 12.35V
3)ignition on: drops under 12V for a couple seconds, then sits at about 12.1V until starting.

Do these seem low? For a month I put on a trickle charger whenever it was in the garage, and it did not seem to change the failure rate. My Bosch 850cca 92Ah is 5yrs old. The battery cables from rear of car drop around 0.5V during starting. Yes, shotgunning a $300 battery is less disagreeable than $1800 HPFP. Thanks for your input.

Same path, then back to 34C after college. Still works.

 

To close out, a new HPFP fixed all issues. No more errors, no "reduced power", no "start/stop disabled". Battery&voltage were not the issue.Summary of the story:
Mid-2021: Reduced Power and Start/Stop disabled occasionally at engine start. Durametric P1031 IMRC and P1023 fuel reg short to gnd. Taking longer to start when cold. Mechanic sees codes but no HP pressure issues over multiple days testing. So I go a year and 10K miles with occasional fails, restart always clears.

Fall 2022: Sometimes fails restart with a check engine. Durametric P053F cold start pressure along with P1031 and P1023/P1026. Sometimes "reduced power" 30 seconds after start instead of immediate. Mechanic confident of bad HPFP, replaced, all good. Starts in under 1 second every time when cold versus 2 or more seconds before.


Cold start after HPFP replaced: under 1 second every time. Center is 10V calibrated and voltage is measured at studs under hood.

 

Dear My Hero,
Well I wont speak to soon yet, but my car is a pain in my ***. Believe it or not I have those same codes, PDK fault, Chassis fault, Engine Fault...and I think PCM or something like that. Anyway seems like my has a similar problem to yours, so I think I will try to replace mine as well. Thank you so much for sharing and being apart of this forum. I will let you and others know how it goes if you still check this forum for updates.

 

FYI - ultimately I took my car to Porsche dealership. They needed to replace the high pressure fuel pump. $4.3K