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Old 06-27-2020, 12:36 PM   #1
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Partially fried immobilizer - possibly?

I recently picked up an '04 Boxster S, I'm new to the Porsche world and new to this forum too. I've been working through a list of small issues while familiarizing myself with the car. Based on reading and rereading a thousand forum posts, I think most of the issues could tie back to the immobilizer (M535), which has very clear water damage (pics below). Oddly, despite these issues and the obviously old water damage, the car still starts without any problem.

If you were in my shoes, would you risk trying to clean the PCB, which seems like it could damage the immobilizer further and potentially kill my ability to start the car? Or would you leave the car as-is and live with these issues? For using ecu doctors or a similar service, would it be in my favor to leave the board alone?

My issues which seem tied to immobilizer:
- remote does not work, central locking switch does not work
- manually locking with key only locks driver door, not passenger, frunk, trunk, or fuel door (trunk/frunk only work with key in ignition so those seem secure-ish)
- alarm does not arm, no honk/beep when locking manually, so likely does not work at all
- dome, trunk and frunk lights dead
- possible battery drain (have checked with multi-meter and not witnessed outsized draw, but battery seems to die if i leave the car alone for ~a week)

I've checked all fuses and replaced broken ones, including the one on the immobilizer.

Thanks for taking a look!

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Old 06-27-2020, 02:13 PM   #2
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You should probably have it repaired as soon as it's convenient. ECU Doctors, or forum member Qmulus can transfer the data from a damaged module to a replacement.

You may be able to restore some function by cleaning it, but you could also do more damage.

Leaving it alone, it will likely continue to degrade and could leave you stranded at an inconvenient place and time.

As a last resort, or temporary measure, you could buy a used matching set of 'M535 box' + DME + key fob with transponder (from an 03 or 04 similar to your car). It would work, but would not have he correct programming for your car's specifics.
I am not an attorney, mechanic, or member of the clergy. Following any advice given in my posts is done at your own peril.
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Old 06-27-2020, 03:09 PM   #3
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Find Qmulus. Like 78F350 said, he can transfer the data from your board to a good one. And he can do it at a fraction of the cost of ECU Doctors. A dealer quoted me $850 for the immobilizer and programming, and if IIRC, that's around what ECU was charging for the repair.
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Last edited by piper6909; 06-27-2020 at 03:12 PM.
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Old 06-27-2020, 03:53 PM   #4
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Thanks 78F350 and piper6909 - really appreciate the quick response and advice - I'll get a hold of Qmulus.
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Old 06-28-2020, 03:30 AM   #5
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I have his number if you want to text me at 512-925-9171
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Old 06-30-2020, 07:49 AM   #6
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Got the PM and responded.

From the corrosion I see in those pictures, it is a bit surprising that your car is still starting. I wouldn't count on it doing it for long.

The different colors that you see are the salts of the different metals on the board that have dissolved. The water itself doesn't destroy the board, but water with electricity creates electrolysis. That is why you lose functionality a little at a time, not all at once. So, if you know you got water under the seat, it is important to disconnect the battery (most important!), remove the seat and remove and dry out the immobilizer ASAP. If it is done quickly, it is likely that you will have no damage. If you leave the battery connected, and the immobilizer wet, then you end up with this type of damage. It is important to clean up as much of the damage as possible, but if you send them to me, I prefer to see pictures of the board BEFORE it was cleaned. That shows me where to look for problems. Note that the worst damage is generally under the relays, and there is NO way to get to that damage other than to carefully desolder the relays clean it, repair the damaged traces and replace the relays. Just removing the relays can take a half an hour just to make sure more damage is not done, and relays that are good are not damaged.

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