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Sebastian Vizcarra
Sebastian Vizcarra, Porsche Meister Tech
Category: Porsche
Satisfied Customers: 350
Experience:  Porsche Factory Certified Master Technician
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Key fob won't open or closed doors car will start but no power

Customer Question

Key fob won't open or closed doors car will start but no power to AC windows gas tank lid turn signals and the onboard menu I get a pop-up that says key is faulty not recognized but I just bought that key brand new from Porsche I took it to them yesterday they said it's not the key it's something electrical any idea
JA: Many things can cause trouble with the A/C. Some simple, some complicated. Fortunately, the mechanic I'm going to connect you with knows all the tricks and shortcuts. Are you hoping to fix this yourself?
Customer: Yes
JA: Great! What have you tried so far?
Customer: Disconnecting the battery
JA: Is there anything else the Porsche Mechanic should be aware of about your Porsche?
Customer: Also brought into Porsche and they simply just said something electrical is going on here the unit that communicates with the key
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 Porsche Mechanic about your situation and then connect you two.
Submitted: 8 months ago.
Category: Porsche
Expert:  porscheguru replied 8 months ago.
Hi, can you tell me what year and model Porsche this is? I can not see any addtl. info for your vehicle. Thanks and I will wait for your reply.
Customer: replied 8 months ago.
04 cayenne turbo
Expert:  porscheguru replied 8 months ago.
Would you agree to a phone service? It would be much easier to talk this through than trying to type.
Customer: replied 8 months ago.
At work doing this...so text is better
Expert:  porscheguru replied 8 months ago.
The remote will start the engine but the remote function is dead? Plus you are stating you are having other issues? The dealer tried to program the remote but they could not? What exactly did they say? Is the remote they tried to program brand new? You can not program used remotes and you can tell if it is new or used by how fast the LED flashes when pushing the remote control buttons. A super quick flash is new and a slow flash is used.
Customer: replied 8 months ago.
New remote...open and start car manully...but no electronics work...cant open close etc
Customer: replied 8 months ago.
Hello
Expert:  porscheguru replied 8 months ago.
Sorry, had to step away a second. Does the led in the door flash when you depress the remote control button?
Customer: replied 8 months ago.
On the key yes.....on the car no
Expert:  porscheguru replied 8 months ago.
Interesting, the remote control functionality is controlled by the Rear BCM or rear body control module. The dealer needs to go into the rear BCM or "Rear/Doors" control unit and see if they can pinpoint the issue. It could be as simple as a coding issue or the rear BCM needs to be replaced. They should also perform "vehicle handover" with the PIWIS tester as that has a tendency to fix weird problems.
Customer: replied 8 months ago.
No flash on led car door...check all fuses including on battery...they are good
Customer: replied 8 months ago.
Where is that located at
Expert:  porscheguru replied 8 months ago.
It is located in the right D pillar area by the amp and cd changer if you have them and right next to the trailer hitch ecu if equipped
Expert:  porscheguru replied 8 months ago.
They also need to check all of the inputs for the door latches to make sure a door latch is not preventing the doors from locking
Customer: replied 8 months ago.
So that BCM unit can interrupt the communication between the car and the key
Expert:  porscheguru replied 8 months ago.
Absolutely, the remote and alarm are in the rear BCM located in the right D pillar area. The drive block or immobilser is located in the KESSY or Immobiliser control unit located above the gas pedal. If you lock the car manually with the key blade in the drivers' door, do all the of the doors lock and does the horn beep and the parking lights flash?
Customer: replied 8 months ago.
no...only the 1 door locks...no flashes and horn doesnt beep
Customer: replied 8 months ago.
Ac/heater doesnt turn on....cant toggle menu on instrument cluster..windows wont go down..cant open rear hatch
Expert:  porscheguru replied 8 months ago.
Let me look at a wiring diagram and get back with you this afternoon Ok?
Customer: replied 8 months ago.
Ok..thanks
Expert:  porscheguru replied 8 months ago.
You stated you have checked all of the fuses but have you checked the 10 amp fuse #23 in the right fuse box?
Expert:  porscheguru replied 8 months ago.
Fuse 31 right is a power supply for the rear BCM 15 amp and fuse 53 left is also connected to the rear BCM
Customer: replied 8 months ago.
Ok....right side fuse box?....i checked fuse box on driver side ....
Expert:  porscheguru replied 8 months ago.
Right side fuse is the main power for the rear BCM. Fuse 31
Customer: replied 8 months ago.
Ok....held up at work now but will check
Customer: replied 8 months ago.
Checked those fuses...and rechecked every other fuse related...all good....managed to get to the bcm....played with it alittle..it set the alarm off and on....didnt notice any flashes...but once connected again...same situation...going to order a bcm just to see if thats it..otherwise im lost...lol..checked all connections to battery and connections to bcm ...all seem good
Expert:  porscheguru replied 8 months ago.
I replaced dozens of the rear BCM on early Cayennes. Many problems related to that control unit including remote control issues. One problem is you will need to have it properly coded with a PIWIS tester. It is now a one flavor control unit 2 button or 3 button remote (2003-2006) and you code it according to your vehicle. 955 618 029 04.
Expert:  porscheguru replied 8 months ago.
Too bad you did not have somebody to scan it with a PIWIS tester to see if the rear BCM even comes up on the control unit list. Water can enter that area from leaking sun roof drains and damage control units, amplifiers, etc. Anything in that area.
Customer: replied 8 months ago.
Quick question....if i order a new or used bcm...does it have to be programmed
Expert:  porscheguru replied 8 months ago.
It could theoretically work if all of the equipment and settings are exactly like yours but it is best to read what coding you have and literally either write it down or save it in the tester and print it out. Then change the new control unit to match your coding. It is bet to have a PIWIS tester to do this and almost essential.
Expert:  porscheguru replied 8 months ago.
Sometimes the rear BCM has corrupt software and the only way to fix it is to read the control unit from a known good vehicleand then write that coding to the corrupt control unit and then change the coding to match. I am not sure why your dealer did not at least look a little deeper for you.

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