Perhaps more of a log to myself on what I looked at, but maybe this will be helpful for someone else out there. Still getting double-flashing of the door LEDs.

Opened the alarm module (unit under passenger seat) this weekend. Measured resistance of the coils on each of the relays to verify none were open/shorted. Resistance of the relays with part number V23072-C1061-A208 and V23072-C1061-A203 were 127 ohms. Resistance of the remaining relay's coil with part number V23072-C1056-A203 was 90.5 ohms. Also, using the pinouts in a similar Tyco V23072-C1061 datasheet (I couldn't find the original Siemens relay datasheet), I checked for stuck open / stuck closed contacts in each of the relays, but they all seemed ok. The only different one was the V23072-C1061-A208 relay at the edge of the row on the yellow connector side whose Normally Open terminals had a measured resistance of 104K ohms (reading increased over time). To me, this suggests a resistor/capacitor in parallel (or other components) rather than a failed relay. I did desolder it just to verify and sure enough, the switched pins were open (which is good).

Also checked for forward voltage drop across all diodes. They ranged from 0.56V to 0.68V. A few measured much closer to 0V, but I think this was due to other components in parallel (measuring them in-circuit) rather than desoldering and then measuring them.

The board had a conformal coating on it, so it was difficult to visually check for discolored / damaged components, but I couldn't see anything to suggest damage / burns.

Also, I used the alarm module sheet over at ecudoctors to check the portion of the harness connected to the yellow 26-pin header going into the alarm unit. I checked resistance from each of these pins to chassis ground. Measurements were as follows (pin numbering according to ecudoctors document). All measurements performed with doors, frunk, rear lid, and glovebox closed.
Pin 1 "Activate / closed": open
Pin 2 "Deactivate / open": open
Pin 3 "Luggage compartment contact": open
Pin 4: not populated
Pin 5 "Rear lid contact": 37 ohms (through engine compartment bulb)
Pin 6 "Speedo signal terminal A": open
Pin 7 "Input 1, rear parcel shelf switch for M 419": not populated
Pin 8 "Input 2": not populated
Pin 9 "Radio alarm contact": open
Pin 10 "Central Locking System position switch 'open'": 0 ohms
Pin 11 "Central Locking System button": open
Pin 12 "Central Locking System position switch 'closed'": 0 ohms
Pin 13 "Radio 1 (ground across alarm horn)": 1 ohm
Pin 14 "Diagnosis 'L'": open
Pin 15 "Diagnosis 'K'": open
Pin 16 "Glove box contact": open
Pin 17 "Input 3": open
Pin 18 "terminal 15": 69 ohms
Pin 19: not populated
Pin 20 "Central Locking System warning lamp": 22.6 ohms
Pin 21 "Door contacts": open (doors were shut)
Pin 22: not populated
Pin 23 "terminal 61": 60 ohms
Pin 24 "External electronics": not populated

At least with nine9six's suggestion, I'm able to at least start the car. Of course, the alarm goes off after a period, but that means I can at least drive it to a garage this week to have codes read.

 

Impressive amount of electronics knowledge you have there. Keep us posted on your progress!

 

1. The immobilizer or the alarm ECU rarely if ever fails.
2. Doing static tests on the ECUs generally yields no results.
3. Since you have the alarm ECU out, you should be able to de-activate it
by simply applying #30 & ground and the unlock function input. As long
as no sensor inputs are a problem, it should not enter the armed mode
and no LEDs should flash nor should the alarm horn sound.
4. Since you were not able to program the immobilizer, you may not have
the correct code, i.e. if it were replaced and the new code wasn't updated
with Porsche.
5. The vehicle can be started with just the immobilizer and with the alarm
unit removed by jumping the starter relay. Obviously the remote must
signal the immobilizer which must then command the DME ECM to enter
the run mode.
6. The immobilizer can be programmed without the alarm ECU connected.
7. 993 owners should always have a spare remote as is the case now days
with all vehicles utilizing electronic keys.

Based on the above, you should be able to isolate your problems to either
of the two ECUs or possibly the wiring.

 

Loren,
Thanks so much for taking your time to chime in!
Best regards to you and yours throughout 2016!

Scrumpy,
+1, on what mpruden said!

Cheers,
Paul

 

As the saying goes; "No news is good news". Seems the OP may have found
his problem, e.g. a simple wiring issue, as no update to the thread.

 

Perhaps Scrumpy is still diagnosing to pinpoint his issue...

I totally agree on how helpful feedback, and a description would be for others!

 

Still no progress. But somehow I missed Lorenfb's post until just now. Will give his suggestions a try. Need further clarifications though...
Perhaps I'm missing a wiring diagram (I am), but I'm not sure what pins "#30" or "unlock function input" indicate. The only decent diagram I've been able to find is the one from the ecudoctors website. Per that diagram, here's what I'm guessing:
- #30 is pin 1 (bottom left as pins facing me with black connector to the left side) on the large black connector. The ecudoctors diagram calls it "terminal 30". It sounds like you're suggesting to ground this pin.
- "unlock function input" - Not sure if you mean to ground another pin here, or if the system outputs this to the immobilizer unit. I don't know what this pin would be.

Is this correct?

My understanding is that since I can go through the programming steps with the key and the immobilizer icon flashes at the correct times (with correct timing) while doing so including at the end constantly flashing while I'm supposed to be mashing the fob button --this indicates that I have the correct code. I was actually given 3 different codes by the dealer. One was 3 digits, one was 4 (the one I'm using), and the other was 5. No idea what the other 2 are for, but the 4 digit one seems to be working (other than my fob perhaps being trash).

This is interesting, though I have questions about my fob's functionality so the fob might not actually be sending the signal. This is easy enough to try though and will at least give me some indication whether the fob is working.

(sigh)

 

Have scheduled an appointment with Hendrick Porsche here in Charlotte for Friday 1/15 to get the codes read out. Need better clues where to focus my efforts. The shotgun method is not working out and I'm running out of ideas. Will give Loren's suggestion a try if I can get more details.

Disconnected the alarm horn and removed the 4 turn signal fuses in preparation of driving it. Using the immobilizer codes and the key-turns routine I can at least drive it. This way, I won't have to listen to the blaring alarm horn and not have the lights flashing on the way to the dealer and back. I get to drive like an official Charlottean --without any turn signals!

 

1. #30 is typically referred to as the constant 12V power. So it and ground
are always present, which just requires a ground input to the unlock pin
of the alarm ECU to simulate the unlock command from the immobilizer.
2. If during the programming operation you reached the point where the LED
constantly flashes, you've entered the correct code and the immobilizer is
waiting for the remote signal. The locks will lock/unlock automatically to
indicate that the remote signal was received. If after that the car won't
lock/unlock nor start, then it's that; the remote doesn't transmit, or either the
immobilizer/alarm ECUs are the problem. A voltmeter on the lock/unlock pins
of the immobilizer will help indicate the functioning of the remote/immobilizer
when the remote is used.
3. Try to obtain 993 wiring diagrams if you plan any further DIY troubleshooting,
without them it's very non-productive.

 

FYI - the Bentley 993 book has wiring diagrams.

 

I had a similar situation in April & it took Porsche of Orlando 27 days to figure it out. I would have Hendicks Porsche call them as I believe they documented the effort & worked with Porsche NA to figure it out. Ended up replacing Control Unit & Alarm control unit . 993-618-159-CX & 993-618-260-03. Also new key fob. Total; $2400 .

 

Good information all.

Lorenfb
Agreed. This is the next item on the to-buy list. Possibly the Bentley manual. I'll likely try what you've described after I get a good diagram to go by. I'm just dealing with fragments of what I've been able to find online, which isn't much. I think I also may have an old Columbus library card that could grant me access to the alldata database, if I find myself in Columbus again.

Jeff Crowley
That's the exact reason why I'm not having Hendrick's do the troubleshooting. On some things it might make sense to me, but an indy garage would be higher on the list than the dealer for those items. For electrical work, I'm somewhat capable. I have a good set of electrical equipment and if all else fails, I can be a parts swapper just as well as the dealer can be --and I don't charge myself labor.

 

Typical, what ever goes in stays in.

 

Went by the auto parts store today and tried their little box that checks for RF from fobs. Tried mine (Bosch RK116, 115 MHz, 99361825902) and no lights on the RF detector. Just to verify that the box worked, I tried my VW key fob and it gets lights.

Additional evidence of a non-functional fob. I do have a new one coming, but the wonderful ebay seller decided to take a week before shipping it. Perhaps I should reschedule my appointment at the dealer tomorrow until I can figure out whether a new fob will solve the problem. Also, bringing a functional fob with me to the dealer may be a good idea.

Does anyone happen to have a schematic for the circuit board in the fob itself? I might be able to pick through it and see if there's anything somewhat obvious.

 

New fob finally came in yesterday. Went through the programming steps and it took the new fob. Amazing how much better a fob works when it outputs RF versus one that doesn't. While the door LEDs were previously double flashing, they now no longer do so. Guess I was just chasing my tail in trying to find a problem that didn't exist.

Note to all: Even through your door LEDs might be double flashing, this could just mean that the immobilizer module never received a disable signal before you used the key to manually unlock the doors. Check the fob.

At least this was a good excuse for me to get to know my new car a bit better. Would've been better spending the time on it doing something otherwise productive, but I did manage to fix some seat switches along the way if that counts for anything. And, I can help answer some questions for other folks having a similar problem.

Thanks to all who chimed in to help!