ceboyd

yes indeed but the immobilizer CODE is programmed into the ECU that talks to the alarm module.. and is not programmed into the alarm module (when you have to reprogram your keys, it is because of changing the keys and you need the code in your ECU)....

....I was able to plug-n-play 3 different alarm modules and all worked fine.... BUT I also had the immobilizer supposedly programmed out of my ECU (yet my key lock/unlock still work fine and my alarm still works as it always did) so it's all a little 'voodoo' to me so I make no claims to know it all about the immobilizer and the 'alarm code'

TRINITONY

This guy explains how things work....

https://rennlist.com/forums/showthre...ht=immobilizer

John Velasco

I have read this before. What I’m looking for is a concept for diagnosing the immobilizer IE what pin should have voltage when. I don’t have a set of factory manuals or I would not be asking. I don’t want to buy an immobilizer if it’s not the problem. I also do not want to eliminate the system. I might be ordering a 997 GT3 and want to have this car spot on.

hidden

Interesting reading. I had no idea that the alarm unit wasn't the immobilizer. My car had the messed up Alarm Unit. I'm not sure my car even has a immobilizer installed. I just know if I unplug the alarm control unit the car won't start. My car is a 1995. The power door locks do not work as I dont have any remote key fobs. Hmm.. Maybe I'm getting my hopes up that I'll actually be able to use a remote to open the door.

grmnxtc

Hidden,

You can add third party remotes to these cars (pretty easy really).

Here's a starting point...

https://rennlist.com/forums/993-forum/122906-remote-door-lock-unlock-installation-into-95-993-a.html

John Velasco

Any one have a last minuet thought?
I’m calling the flat bed and sending it to the dealer.

jv

hidden

Does anyone have a picture of the immobilizer unit itself? I always thought the Alarm Control unit was the immobilizer but I guess I'm wrong. I actually got my door locks to work today with the new alarm control unit. I just need to add the additional function of a remote key fob.

So my question is, what unit is the receiver for the remote key fobs?

ceboyd

the immobilizer was a function of the ECU I thought..

Is there a different box for just the immobilizer?

If there is, I never knew about it or which box it is...

John Velasco

The Immobilizer is just right of the DME under the driver’s seat. The immobilizer receives the input from the remote and sends a signal to the alarm module, if all is well with the sensors the Immobilizer will send a ground signal to the DME to allow the engine to crank. If something is wrong with the sensors or with the ignition key chime switch we will have a failure to start and a noise. I may have a sequence out of order here, but its close enough. My problem was not having the wiring diagrams to diagnose the problem. I still am not sure if you have to drill the rivets on the DME cover to remove the immobilizer. This cover is the reason you can’t see the Immobilizer with the seat in.

jv

Lorenfb

"here's a photo to show you exactly how the immobilizer module looks.. I have a spare FS still if you need one." - ceboyd -

No, that's just the alarm module which just controls functions commanded
by the immobilizer. The immobilizer is under the metal plate under the driver's
seat. the rivet nuts must be cut to be removed.

The immobilizer sends a command to the DME to allow a "running" mode and
commands the alarm unit to allow cranking. Most likely the 4 digit code has
been removed from the immobilizer at installation.

Bottom line: The immobilizer should be the LAST element to be considered faulty.
That's unless the car is a cab and the unit got water damaged.

TRINITONY

So there may be the possibility of the code being under it? Why I'm asking is that I'm uncertain whether my car has the original immobizer.

Lorenfb

In most cases the code is removed from the unit.

If the immobilizer(alarm) light goes out when the remote is depressed, then most
likely the immobilizer is O.K. Then the problem could be the clutch switch, as mentioned,
or the alarm unit which drives the starter relay which drives the starter solenoid.

There's an emergency procedure for starting the 993 as outlined in the owner's
manual by locking & unlocking the driver's door without using the remote.
Verify this by reading your manual.

TRINITONY

Tks..

John Velasco

Thanks for the input. I tried all of your suggestions but I don’t even have the light illuminating. I can’t use the emergency procedure, so therefore Me thinks I will be buying a new Immobilizer. Your input on previous threads helped me to this conclusion.
jv

Lorenfb

A bad functioning ignition switch can affect the access "into" the immobilizer
for programming, besides the case of not having the correct access code.
If the remote/immobilizer can set/reset (lock/unlock) the car, then there's
a likelihood that the immobilizer is O.K., but reprogramming is problematic
because of other issues, e.g. the ignition switch or the access code.