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THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHMy immobilizer no-crank no-start fix for 2,50
Reported or suspected cause
no crank no start
Reported cause
No successful repair reported for this finding.
1
Identified cause
0
Suspected cause
0
Reported fixes
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Reported cause · Original poster
the original issue was a no crank no start because the startlock relay is also guarded by the immobilizer.
Leading evidence: 'no crank no start' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'no crank no start' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Replace dme and immobilizer, or 1500' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Suggestion · Original poster
Porsche specialist quoted me 2500 for replacing the dme and immobilizer, or 1500 for installing a used set.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
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Suggestion · Original poster
In another topic i shared my issue but like in all other topics i saw about my problem it ended up in replacing the immobilizer which is expensive.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
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Suggestion
Any advice for those who aren't familiar with soldering/replacing said relay?
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
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Suggestion · Original poster
A common way to test a stuck relay is to tap it a few times, and yes it got unstuck and the car fired right up
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
5 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.
0 acknowledgements have no verified action link; they do not establish a repair result.
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I would like to share my search and solution in fixing my immobilizer. In another topic i shared my issue but like in all other topics i saw about my problem it ended up in replacing the immobilizer which is expensive. And i found my issue and got the solution for 2,50.
To start with the issue: it is a no-crank no-start. Mostly seen with water damage at the immobilizer, but mine had no water damage and looked like new (although it was still the original from 1999).
The fault codes:
DME faultcode 39: Anit-drive-off feature (no signal)
Alarm faultcode 21: W line (DME immobilizer), open circuit
Alarm faultcode 49: k-line, short circuit to ground
This basically tells you there is 1 issue, the w-line (port 23 on the immobilizer, port 88 on the dme) has an issue.
The 3the error is related. the dme uses the w-line also for diagnostics, this is (as far as i have been able to trace back) done via (or at least together with) the immobilizer.
Since k-line and w-line are next to each other on the immobilizer i was thinking it is shorting out somewhere. and after measuring the cables i concluded it is shorting out inside the immobilizer. Here my knowledge stopped.
So i looked at the options:
Porsche specialist quoted me 2500 for replacing the dme and immobilizer, or 1500 for installing a used set.
An ecu specialist would replace it for 1000
I found someone who could flash out the immobilizer for 650 (but this would result in a permanent cel)
Then I found a company that can install a simulator in the dme to mimic the immobilizer for 350 but this includes cutting the diagnostic lines which makes it hard to diagnose the dme in the future.
After all of this i actually realized I work at a company that creates 1 of the worlds most complicated electrical machines and i have a team member that is an electrical specialist. So i asked him if he could have a look. Apparently 1999 electronics are a walk in the park for him.
Within 10 minutes he located the faulty component, the 6 pin 5v relay on the left bottom. It is used to switch on the k and w line. if it is stuck, the w-line signal will leak onto the k-line causing it to think it is shorted to ground.
A common way to test a stuck relay is to tap it a few times, and yes it got unstuck and the car fired right up
I ordered the part (2,50) replaced it and the car is working properly again.
I did make pictures during the diagnose, but not after i put n the new relay, i was to impatient to test it.
For the movie showing the tapping to get it started, i had the start lock and clutch switch bridged to be able to test it like this. the original issue was a no crank no start because the startlock relay is also guarded by the immobilizer.
Brilliant!!! Nice find! I am sure this will help others in the future. You were fortunate enough to either do yourself or have someone who can replace that relay. Any advice for those who aren't familiar with soldering/replacing said relay? Is it difficult?
Good luck!
They are 90's technology, the relay has pretty thick legs which is easy to de-solder you need some de-solder wire (copper) and a 30-60 watt soldering iron. Took me about 10 minutes without real experience.
