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Re: Key Won't Start Car (Intermittent)

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It has happened twice this week. Have a 2009 PDK. Car is in park, foot on brake pedal, turn the key and nothing. All the dash lights display, idiot lights on, but no clicking/cranking noise. Just dead silence. Turn again, same result. I remove the key, open the door and start over. Fires right up. Do I need a new batter for the key fob? Is the starter going (pun intended)? A switch/relay in the brake that tells the car's brain that the brake pedal is depressed (owner isn't at this point)? Or, just weird coincidence? Thanks.
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db997S
It has happened twice this week. Have a 2009 PDK. Car is in park, foot on brake pedal, turn the key and nothing. All the dash lights display, idiot lights on, but no clicking/cranking noise. Just dead silence. Turn again, same result. I remove the key, open the door and start over. Fires right up. Do I need a new batter for the key fob? Is the starter going (pun intended)? A switch/relay in the brake that tells the car's brain that the brake pedal is depressed (owner isn't at this point)? Or, just weird coincidence? Thanks.

The battery in the key fob plays no role in engine starting. The battery is just there to provide enough juice for the RF circuit to send a signal when you press a button on the fob to lock/unlock the car.

There is an RFID "pill" in the key fob that when you turn the key to start the engine receives an RF transmission from the car's security module. The antenna is behind the key surround. This signal energizes the RFID pill and it responds with an RF transmission in which its ID is encoded. The transmission is picked up by the antenna behind the key surround and carried to the security module which extracts the ID and compares it to the ones stored in its non-volatile memory. If the ID is found then the engine may start provided other conditions are met.

The next time you go to start the engine and it doesn't start:

Try turning the key off and wiggling the key moving it about to see if when you try to start the engine again if this makes a difference. If it does then ignition switch is suspect. If the car key is part of a heavy key chain the ignition switch can fail rather early.

Try turning the key off and releasing then depressing the brake pedal -- several times -- to see if when you try to start the engine again if this makes a difference. If it does then brake pedal switch is suspect. (As an aside you need to "check" the brake light switch once in a while to make sure it is ok. I do this by using the windows at work and observing the behavior of the brake lights in the windows when I gently press on the brake pedal. What I have seen -- with my Boxster -- is the brake lights may not come on until the pedal is pressed quite a ways. Or the brake lights may not come on at all. The brake light switch (and other switches that are activated by the pedal hardware) can and do wear out.)

Try turning the key off then moving the PDK shift lever about then back in Park to see if when you try to start the engine again if this makes a difference. If it does then the switch that recognizes the PDK is in Park is suspect.
Does this behavior happen when you have just unlocked the car? Reason I asked is that I had a strange electrical experience, battery drained when the car sat for 5 days in my garage unlocked, and the service advisor told me that it's best to have the car locked even in one's home garage. Something about the car going into a "sleep" mode. there was no problem found and I have not had the problem again.
I never lock my Boxster in the garage and have only seen a problem with battery discharge when my ignition switch started failing,
Yes, but it was only while at work, so way less than 5-day sleep mode.
Well, the car acts like it thinks it is not in park. I don't have PDK, but I assume there is some indication on the dash that it's in "P". Next time this happens check that the indication is there if you haven't done so already.
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