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Need advice on blown fuse / bad circuit

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3 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis

THIS DISCUSSION / SOURCE-DERIVED OVERVIEW

Discussion summary

YOUR RESEARCHNeed advice on blown fuse / bad circuit

Leading reported evidence

Install spare 30 amp fuse, and it immediately blew

Performed · outcome unconfirmed

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

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.

Discussions that performed work without a confirmed outcome: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Performed · outcome unconfirmed · Original poster
Installed a spare 30 amp fuse, and it immediately blew.
Original post Read captured discussion
Need advice on blown fuse / bad circuit

Frequently discussed work

Disconnect coils one by one

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that contain suggestions: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion
- Disconnect the coils one by one
Original post Read captured discussion
Need advice on blown fuse / bad circuit

Read full discussion summary

Leading evidence: 'Install spare 30 amp fuse, and it immediately blew' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'somewhere downstream' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Disconnect coils one by one' (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.

Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.

Read captured replies

1 matching discussions · 3 captured posts examined · 0 partial discussions

Compare 4 other evidence results

Run perfectly, daily driver, no issues, no cel codes, etc

Performed · outcome unconfirmed

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that performed work without a confirmed outcome: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Performed · outcome unconfirmed · Original poster
Prior to this, ran perfectly, daily driver, no issues, no CEL codes, etc.
Original post Read captured discussion
Need advice on blown fuse / bad circuit

somewhere downstream

Suggestion or failed attempt

No successful repair reported for this finding.

0
Identified cause: 1
Suspected cause: 0
Reported fixes

Read evidence and context

Discussions that suspect a cause: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suspected cause
If it does not, your problem is between the fuse and the relay, else your problem is somewhere downstream.
Original post Read captured discussion
Need advice on blown fuse / bad circuit

Disconnect coils one by one

Suggestion or failed attempt

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that contain suggestions: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion
- Disconnect the coils one by one
Original post Read captured discussion
Need advice on blown fuse / bad circuit

Disconnect o2 sensors one by one

Suggestion or failed attempt

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that contain suggestions: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion
- Disconnect the O2 sensors one by one
Original post Read captured discussion
Need advice on blown fuse / bad circuit

Frequently discussed actions (4)

These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.

Disconnect coils one by one

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that contain suggestions: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion
- Disconnect the coils one by one
Original post Read captured discussion
Need advice on blown fuse / bad circuit

Disconnect o2 sensors one by one

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that contain suggestions: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion
- Disconnect the O2 sensors one by one
Original post Read captured discussion
Need advice on blown fuse / bad circuit

Install spare 30 amp fuse, and it immediately blew

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that performed work without a confirmed outcome: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Performed · outcome unconfirmed · Original poster
Installed a spare 30 amp fuse, and it immediately blew.
Original post Read captured discussion
Need advice on blown fuse / bad circuit

Run perfectly, daily driver, no issues, no cel codes, etc

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that performed work without a confirmed outcome: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Performed · outcome unconfirmed · Original poster
Prior to this, ran perfectly, daily driver, no issues, no CEL codes, etc.
Original post Read captured discussion
Need advice on blown fuse / bad circuit

Reported and suspected causes (1)

These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.

somewhere downstream

No successful repair reported for this finding.

0
Identified cause: 1
Suspected cause: 0
Reported fixes

Read evidence and context

Discussions that suspect a cause: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suspected cause
If it does not, your problem is between the fuse and the relay, else your problem is somewhere downstream.
Original post Read captured discussion
Need advice on blown fuse / bad circuit

Coverage and how to read this overview

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.

3 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.

Generation: 20261027T035758Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources

POST 1 / ORIGINAL POSTEROriginal post

I have a 1999 996 C2 Coupe which I bought new in May of 1998. It recently stalled in a store parking lot; checked fuses and found a 30 amp fuse in position "C2" was blown. Installed a spare 30 amp fuse, and it immediately blew. The fuse position is for "ignition, fuel injection, and oxy sensors" circuits. Other than a short in the wiring harness somewhere, is there anything related to the individual injectors, individual coil packs, or sensors that can fail and trip a 30 amp fuse? All injectors and coil packs are original, 16 years+ and 160,00+ miles. Prior to this, ran perfectly, daily driver, no issues, no CEL codes, etc. Thanks in advance for any advice on best place(s) to start tracking this down. jm

POST 2Original post

The short can be anywhere on that circuit so we need to isolate each part of the circuit. First go get some smart fuses. Plug a 30A one in and let it blow. Now the fuse (LED) should light up. You also need the wiring diagram here http://download.qclt.com/PORSCHE/man..._1999_2000.pdf Basic power flow: fuse c2->injection relay->O2 sensors/coils/injectors->X59 connector->DME->ground ("/" means things connected in parallel) You can disconnect the injection relay first and see if the LED goes out. If it does not, your problem is between the fuse and the relay, else your problem is somewhere downstream. Plug the relay back in and do the following until the LED goes out. - Disconnect the O2 sensors one by one - Disconnect the coils one by one Let me know what you find first before we go deeper.

POST 3 / ORIGINAL POSTEROriginal post

Ahsai, Thanks for your advice. Much appreciated, I will start with the relay and go on from there, if required. Wiring diagram was a big help. jm

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