Door lock, windows, alarm problems

[Heavydee]

Hi, everyone,  I have tried to research these topics, but I am sort of at my wits end. My car is a 1999 Boxster with manual transmission with 131,000 miles on it. All of a sudden, the windows and door locks started to act very wonky. If I try to lock the car with the fob, you can hear the mechanical whizzing of the locks and then a double beep from the alarm, and the doors do not lock The lock button on the dash does not work. The driver's side door will lock with the key, but not the passenger's side. the windows are very peculiar. If they are both down, and I put the passenger side window up all the way, the driver's side window will go up without touching the button.

My mechanic pulled codes, and this is what he got:

Airbag:
03 -- Airbag warning supply
29 -- ignition circuit-side airbag, driver
49 -- belt buckle, passenger
46 -- belt buckle, driver
31 -- ignition circuit-side airbag, driver
21 -- ignition circuit, driver
45 -- belt buckle, driver

Alarm System:
25 -- terminal 86 is not detected
36 -- passenger compartment monitoring sensor
42 -- wrong key or wrong transponder pill
11 -- voltage failure during alarm output
10 -- voltage failure at terminal 30 with alarm system active
46 -- control locking synchronization
34 -- passenger compartment monitoring sensor
47 -- control locking synchronization
58 -- tank servo motor not energized despite relay activation
61 -- central locking limit position unlock not reached

He suggested that I should replace the M535 ECU. I have checked all of the related fuses, and I have checked the fuse on the M535. I opened the M535 box, and cleaned everything the best that I could. There were definitely signs that there had been water in the box.

The car runs and drives, the convertible top works fine, I just can't lock the doors and set the alarm. Does this sound like it is an issue with the M535 box or more of the door locking mechanisms? Or, is it due to the electrical part of the ignition switch? Any suggestions, or ways to troubleshoot would be appreciated.

Thanks,
Rob

1999 Boxster, Arctic Silver over red, 5sp manual

[JFP in PA]

The central locking computer is toast.  It may be repairable, but that could end up costing more than getting a new one and having it programmed.

 

Good luck and when you are paying for the new unit, remember that Porsche sells a $20 part that prevents this from happening:

 

 

[Heavydee]

Thanks, JFP, for your reply. I've owned the car for about three years, and have always kept it garaged. I didn't know about the issue of the drains until now. I have seen the cost of a new ECU, but do you have an idea of what it costs to get a new one programmed by a dealer?

[JFP in PA]

1 hour ago, Heavydee said:

Thanks, JFP, for your reply. I've owned the car for about three years, and have always kept it garaged. I didn't know about the issue of the drains until now. I have seen the cost of a new ECU, but do you have an idea of what it costs to get a new one programmed by a dealer?

 

You are looking at around one hour of diagnostic time, and as dealer hourly cost vary with geography, which can be anywhere from around $150 to as much as $300.

 

The problem with the convertible top well flooding has been well known and documented since the early 2000's.  The well under where the tops stores is well designed to collect water and funnel it to the two drains that drop it under the car.  Problem has been from day one that these drains quickly become plugged with grass clippings, leaf debris and the like, resulting in the well becoming flooded.  When the car is in motion, and the brakes are applied, a wave of the trapped water sloshes over the well lip and directly under the driver's seat where the central locking module lives.  Around 2001-2002 Porsche realized there was a significant problem (due to the number of modules they were replacing under warranty) and released the specially contoured screens to protect the well drains.  Having installed a ton of these screens, you would be amazed at how many cars had either one or both drains completely plugged, and even had standing water in the wells.  The preventative fix is simple: Clean out the drains with compressed air and/or soapy water, then plug in the screens.  Problem solved, I have had them in my personal car since they were released, and drains have never needed cleaning again................😉