9Y0 common problems and failures
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Does anyone know what the codes P1D7400 and P1D7500 are? My 2025 Cayenne S mentioned above (cylinder misfiring and battery issues on 800 mile new car) is still in shop and not sure what is planned to give me comfort that car is reliable in light of starting/battery issues. These two codes came from service tech and are in addition to the various P0300, P0302 and P304 codes I saw on my OBD scan. Any thoughts appreciated!
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From: northwest US, but also victoria b.c. and nyc
Does anyone know what the codes P1D7400 and P1D7500 are? My 2025 Cayenne S mentioned above (cylinder misfiring and battery issues on 800 mile new car) is still in shop and not sure what is planned to give me comfort that car is reliable in light of starting/battery issues. These two codes came from service tech and are in addition to the various P0300, P0302 and P304 codes I saw on my OBD scan. Any thoughts appreciated!
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From: linker Fahrbahn
Misfire can happen from many causes small and large.
Loose or paint-covered ground point, loose ignition coil connector or burned and broken valve, bad hpfp etc etc. Need an exhaustive diagnosis.
Loose or paint-covered ground point, loose ignition coil connector or burned and broken valve, bad hpfp etc etc. Need an exhaustive diagnosis.
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Does anyone know what the codes P1D7400 and P1D7500 are? My 2025 Cayenne S mentioned above (cylinder misfiring and battery issues on 800 mile new car) is still in shop and not sure what is planned to give me comfort that car is reliable in light of starting/battery issues. These two codes came from service tech and are in addition to the various P0300, P0302 and P304 codes I saw on my OBD scan. Any thoughts appreciated!
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From: northwest US, but also victoria b.c. and nyc
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Thanks everyone for info! Dealer says all codes erased and cannot find reason for the misfires or the battery discharge fully next morning. They want me to drive to see if it happens again. It is a little over a month old! I said unfair for me to cross my fingers and hope it doesn’t happen again! Discovered P1D7400 and P1D7500 relate to possible cat damage due to frequent misfires. They said it only happened once. But I started, it labored for a few min and then I shutoff and restarted to same problem. Did this sequence maybe 5 times before it corrected. So imho it was misfiring for at least 15 min. At 500-700 RPMs, misfires occurred about 8-11 thousand times. Speaking with GenMgr Monday to discuss where we go from here. They don’t want to diagnose without more!?
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From: linker Fahrbahn
Thanks everyone for info! Dealer says all codes erased and cannot find reason for the misfires or the battery discharge fully next morning. They want me to drive to see if it happens again. It is a little over a month old! I said unfair for me to cross my fingers and hope it doesn’t happen again! Discovered P1D7400 and P1D7500 relate to possible cat damage due to frequent misfires. They said it only happened once. But I started, it labored for a few min and then I shutoff and restarted to same problem. Did this sequence maybe 5 times before it corrected. So imho it was misfiring for at least 15 min. At 500-700 RPMs, misfires occurred about 8-11 thousand times. Speaking with GenMgr Monday to discuss where we go from here. They don’t want to diagnose without more!?
It’s a new car so warranty will cover the cost if any. Time and inconvenience will be incurred so practice your best patience skills.
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From: northwest US, but also victoria b.c. and nyc
@TGKelly and get an antigravity sc-10 charger. rule out battery. why would you not do that?
if your vehicle had a misfire condition that is ongoing it will reoccur.
also, buy good gas, that can’t hurt. i buy gas from a cool locally owned station where they work on tons of older porsches and classic cars. they are very clean and picky. they say hi when you come and they sell 92 octane ethanol free gas. does it pencil cost wise as far as mileage, no. but, i have talked to them - they maintain their pumps and are very quality conscious. and it seems like i do get an extra mile per gallon w ethanol free. you don’t have to buy ethanol free. shell is what i go for out of i am out of area. no costco, nothing wrong w costco, it just bugs me that they only sell 91 - they claim it tests higher, but if that was true all the time it would be labeled higher.
if your vehicle had a misfire condition that is ongoing it will reoccur.
also, buy good gas, that can’t hurt. i buy gas from a cool locally owned station where they work on tons of older porsches and classic cars. they are very clean and picky. they say hi when you come and they sell 92 octane ethanol free gas. does it pencil cost wise as far as mileage, no. but, i have talked to them - they maintain their pumps and are very quality conscious. and it seems like i do get an extra mile per gallon w ethanol free. you don’t have to buy ethanol free. shell is what i go for out of i am out of area. no costco, nothing wrong w costco, it just bugs me that they only sell 91 - they claim it tests higher, but if that was true all the time it would be labeled higher.
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Thread Starter
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From: linker Fahrbahn
Updated list:
- .1 lurching, surging or lurging when downshifting - believed to be related to the dual mass torque converter damper and lockup clutch release programming. Most noticeable with light braking 3–>2 downshift. After entering 2nd gear the lockup clutch releases and engine inertia creates a torque surge. Lockup clutch status can be seen live with an OBD device. https://rennlist.com/forums/cayenne-...own-shift.html
- .1 6th gear vibration or shudder - believed to be related to the wet multi-plate torque transfer clutch mounted on the rear of the transmission - mainly affects V6 powertrains. https://rennlist.com/forums/cayenne-...vibration.html
- controllable water pump shroud seal failure - causes collateral damage to the vacuum system - can affect V6 and V8 engines. Can occur with no CEL and no overheating. Can be observed by low coolant level in the reservoir and dried coolant on any component for example coolant shutoff valve or vacuum solenoids. Also experienced on Audi RS5 and Macan installations. https://rennlist.com/forums/cayenne-...how-often.html
- oil vapor separators - regular maintenance item on all modern German direct injection engines - can cause excessive crankcase vacuum or pressure which can fail seals and gaskets - can affect V6 and V8 engines. DIYable. https://rennlist.com/forums/cayenne-...r-failure.html
- .1 Porsche Surface Coated Brakes - squealing, no known solution other than changing to standard rotors and pads. https://rennlist.com/forums/cayenne-...ueal-pscb.html
- early .1 LiFePO4 main battery - can fail prematurely - members have reported the battery is replaceable under warranty. Late .1 and all .2 use AGM batteries. Aftermarket conversion to AGM is possible. https://rennlist.com/forums/cayenne-...e-battery.html
- PSCB noise complaints when new and apparently an emerging issue with “bumps” on the rotors as they age. Porsche no longer offers PSCB so it suggests they are aware of the problems. No solution to noise, warranty rotor replacement with “bumps” might be possible depending on the dealer and your persistence. https://rennlist.com/forums/cayenne-...nne-turbo.html
- broken turbo wastegate lever near 100k miles. Lever is not replaceable but one sote member has done a welded repair. Turbo replacement required if weld repair is not done. https://rennlist.com/forums/cayenne-...l#post19613294
- leaking coolant shutoff valve <50k miles https://rennlist.com/forums/cayenne-...l#post19686057
- early .1 PCM5 screen goes black without warning. Eventually it reboots itself and returns to normal function.
- bubbling "PORSCHE" lettering in .1 rear light bar https://rennlist.com/forums/cayenne-...ht-defect.html
- .1 leather dash lifting. Too early to know if this affects .2. https://rennlist.com/forums/cayenne-...ash-issue.html
- oil filter housing gasket leak. Detectable from signs of oil in the engine valley near the oil filter housing-engine block interface. Cause is collapsed/failed gasket. DIYable repair. https://www.audiworld.com/forums/aud...grade-3065401/
- weak front upper control arms. Bushings are torn <<100k miles. Causes wandering and steering vagueness. DIYable. https://rennlist.com/forums/cayenne-...the-right.html
Last edited by chassis; May 21, 2025 at 09:45 PM.
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Need Help 2025 Cayenne S Coupe Not Starting UPDATE
Thanks again to everyone for advice and info! Dealer said Porsche would not authorize additional diagnostic work and wanted me to just drive it and see. I politely gave dealer a list of other Cayenne S models available in the area as well as GTS models that I would accept on trade. I simply argued the car failed to start 33 days into ownership so I was “revoking my acceptance” of it under Uniform Commercial Code. Dealer is great… few days later agreed to allow $ for $ trade into new one. I upgraded to GTS (paid diff) and love it so far. Unfair of Porsche to expect new owner to “test drive” new car to see if it fails to start again! Either find and fix root cause of problem (restoring confidence) or take back… seems right thing to do.
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From: northwest US, but also victoria b.c. and nyc
Thanks again to everyone for advice and info! Dealer said Porsche would not authorize additional diagnostic work and wanted me to just drive it and see. I politely gave dealer a list of other Cayenne S models available in the area as well as GTS models that I would accept on trade. I simply argued the car failed to start 33 days into ownership so I was “revoking my acceptance” of it under Uniform Commercial Code. Dealer is great… few days later agreed to allow $ for $ trade into new one. I upgraded to GTS (paid diff) and love it so far. Unfair of Porsche to expect new owner to “test drive” new car to see if it fails to start again! Either find and fix root cause of problem (restoring confidence) or take back… seems right thing to do.
