996.2 door latch confusion

Hello! I'm finally embarking on fixing the door latches in my new-to-me 2002 C4S, but I'm not sure of the actual issues: Driver's door: Locks and unlocks fine (physical key and interior button). Pulling either door handle lowers the window properly but the window goes back up when I let go of the exterior door handle. The interior door handle works fine most of the time. I used a PIWIS III to verify that the door lock state is correct and that the "door open" state goes from closed to open back to closed when using the exterior handle. I'm guessing it's the outer microswitch on the door latch (which checks the door open/close state) but still confused why it works for the interior door handle (most of the time). Has anyone seen this before? Passenger door: Locks just fine with key and interior button. Need to pull the interior door handle to unlock. Window never lowers. PIWIS shows locked and closed no matter what I do. If I try to unlock the car with the interior button (or when the car tries to unlock on engine off), the latches seem to unlock, then lock again, and the horn beeps twice. My best guess is the inside microswitch (which checks the door lock/unlock state) is stuck on the lock position. Key remotes: I have both original keys. The car unlocks and starts with the physical keys just fine. The LED on each key lights up when I press either button but no communication at all with the car. I have heard that lock issues can lead to remotes not working. Is this a likely issue or are the keys just dead after 23+ years? Appreciate any advice!

Quotes source post: 20061741

It will drive you nuts trying to figure out the why and where of all the micro switches/DME/BCM that are controlling the door/windows/central locking system. From your above explanation, just change out the latches with some new inexpensive URO ones. That should fix at least part of your problem maybe all of it except the key fobs. Similar problems got fixed for me with correct URO part # latches. The left is different than the right. They've worked perfectly for me in 2 cars now for years. Its amazing how much those latches control everything you're complaining about. Your key fobs circuit board is gone. You need new fobs, but keep the pills and blades they are still good and needed. You will need the IPAS codes from the Porsche dealer for your vin car and the key codes that should come with official new fobs. You'll need To program the fobs with PIWIS. Or pay someone to program them, an expensive proposition usually... jmo

Quotes source post: 20061799

Makes sense. I already got the driver side URO latch but it seems that URO doesn't make one for the 996.2 passenger side. VEMO makes this part (OEM # 3B1837016) but I'm not sure if it fits 996s (# 3B1837016 P ). I found the microswitches that Porsche uses on mouser and ordered a bunch. I'll try replacing just the switches before I spend $600 on a new latch. The key fobs are a bummer. The previous owner actually provided a replacement fob (complete with the code) but I haven't had any luck getting the IPAS codes from the Porsche dealers around here unfortunately. Thanks for your response!

Audi TT from the same era are a straight swap and can be had for 20-30USD Just note that L/R door lock mechanisms have different part numbers for LHD and RHD cars.

Quotes source post: 20061859

Interesting. I looked it up on the URO catalog and found this (sku 13372, OEM # 8N1837016C). It says compatible with Porsche 996 but only w/o M535. I read on the door latch replacement thread that VW parts disable the remote fob. Is it safe to assume that this will lead to similar results?

Quotes source post: 20061897

My driver's door issue was the window wouldn't remain down when the door was open. I.e the door didn't know it was open so it raised the glass. I replaced with this https://www.ebay.com.au/itm/194438952958 My remote button still works fine I don't, however, have M535 on my car

Ah. Got it. I believe the locks are only different for the passenger side. How can I tell if I have M535 in my car? Doesn't say anything on the VIN decoder.

I found a sticker in my owners manual that listed the options my car came with. I think there's also a sticker on the underside of the hood. For me LM7X (colour Atlas Grey) C23 226 288 411 601 635

I�m pretty sure the M535 is referencing the version of the immobilizer module. https://www.ebay.com/itm/326159276235 The two options are either M534 or M535. I don�t know if there�s another way to find out, but the most straightforward method is to take a look at sticker on the module itself. You�ll need to remove the seat to do this, but if you have a videoscope you could just stick it in beneath the seat and try to read the sticker.

Looking at the 996 PDF for parts - part 14 is the door lock. The last column is blank which would indicate that there's no special door lock for cars with M535

I know that we are deep into the $ saving mode. When I have these issues, the only parts I would buy is from a Porsche dealer. I am not rich, I just don't want frustration of having to rip out the door twice or three times.

Thanks for all the guidance, folks! From what I have uncovered, 3B1837016 P is the part for our 996s, but similar parts 3B1837016(C) are used in Audis and Volkswagen that seem to disable the remote fobs. And while it will probably just make more sense to just get the OEM part and resolve the issue once and for all, the engineer inside me doesn't want to give up without a fight (i.e. replacing just the microswitches). With that said, I started with an easier task and managed to get the IPAS codes from a local porsche dealership (just had to show them my title and driver's license to prove that I own the car), and I was just able to program the spare key fob that the previous owner had included with the car. The fob is from a 986 and so has buttons for both the front and rear hatches (neither of which do anything) but at least I'm now able to unlock the car with the fob and the alarm doesn't go off if I don't insert the key into the ignition within 10 seconds of opening the door. I've also been troubleshooting the passenger door with the PIWIS. It seems that the alarm module is just reading locked/closed from the door no matter the state. Unlocking the car with the key fob or the interior lock button results in a double beep but the passenger door does still unlock. Locking with the fob or the interior button works just fine. So I'm going to try replacing both the open/close microswitch as well as the locked/unlocked microswitch.

Alright. I will take all the "I told you so"s. After some investigation, I realized that the switches inside the latch were different than the switches outside. I decided to do something really stupid (at least in hindsight) -- I bought a used original passenger side latch from ebay. After one somewhat frustrating but fairly straightforward hour, I had the latch installed and... the passenger door now has the same problem as the driver door -- the windows drop down but don't stay up. However, at least the passenger door can be opened without starting the car and lowering the windows manually. At this point, I have a key that works perfectly, no more horn beep when I unlock the car, and both doors are operational with quirks. I'm honestly fairly happy to leave both doors as is. It gives the car some character. Thanks for all the advice folks!