And yet another key fob/immobilizer question
 

Searched every post on here, Rennlist and anything on Google. None seem to be the same.
The history: No problems with the Boxster for a long time, everything working well. Parked it in the garage for about a week and a half. Went to move it out the other day and it wouldn't start.
Symptoms: Turned the key on, everything lit up as usual. Turn to START, nothing.
What works: Ignition lights come on, radio works, horn, heater, etc.
What doesn't work:
1. Central locking and trunk switch from key FOB does nothing. FOB light flashes, but no response. Security light on dash does not light. Replaced the battery just in case.
2. Valet key does the same.
3. Central lock does not work from button on dash with either key.
4. Windows do not automatically retract when opening door, no raise or lower from the console buttons.
What I've done so far:
1. Battery voltage is good at 12.8 volts.
2. Disconnected battery to try for a reset
3. Checked all fuses for continuity with a voltmeter. Even the one on the Immobilizer.
4. Disassembled Immobilizer from under the seat (looked clean and dry), disconnected, cleaned and reseated connectors. Wiring harness looked good and intact. Cleaned circuit board with contact cleaner.
Codes listed from Durametric:
1. P1571: Immobilizer, open circuit or no signal.

Ideas?
GaryD

Yeah:

P1571 Immobilizer - Open Circuit / No Sign Possible causes: - Open circuit in wiring between DME / no signal. control module and alarm system. - Short circuit to ground or short circuit to B+. - Alarm system control module faulty.

JFP: I don't expect an answer from you because you'll be insulted but, you're telling me to do what I've already done. Thought maybe I'd get an insight into where to look next or which wires to test.

No, I don't get insulted, but I did tell you exactly what the Porsche OBD II diagnostic's manual indicates are the probable faults. I did not offer to reproduce the wiring diagrams, as that would constitute a violation of both the forum rules, and an infringement on PCNA's intellectual property rights.

To test the circuits involved, you need Porsche special tool 9616 (pin out box) and need to follow about three pages of specific tests covered in the OBD II diagnostics manual. Very few individuals have access to the tools and reference sources involved, so detailing everything covered in the manual (which would be a similar violation to those mentioned above) probably would not have helped you very much as they do not get into wire identification during the testing procedures, but utilized the pin reference numbers in the special tool 9616 pin out box to complete the tests.

I would suggest you get access to a Bentley manual for the car and try tracing the wiring from the wiring diagrams in the back of the book, which should allow you to identify and test the wires and circuits outlined in the possible fault causes list I provided.

Thanks JFP,
Seriously, I appreciate the answers (most!) of what you give, you know your stuff! Just seemed a bit vague. I have the Bentley and have been tracing the wires today. As I get chance (between other projects), I'll let everyone know how it turned out. My wife wants to know why her daily driver is down. For now, she has to suffer driving the BIG car, 1994 XJ12 6litre!! (has to pay for her own gas). :dance:
Seriously, if you ever want to build a British icon car, PM me!! On a side note though, just finished restoring a 1965 GT 350 Shelby for the original owner. Car was stolen 30 years ago and recovered 5 years ago. Ground up redo.

I've spent some time staring at the wiring diagrams as well, the following references the designations from the diagrams; I would be looking at the signal circuit that runs from pin#88 on the DME to pin #1/23 on the immobilizer, and checking it for continuity and a possible short to ground. I would also be looking for connector X 3/1, which is on that circuit, to make sure it has good contact.