911uk

wierd pcm 1 behaviour

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

THIS DISCUSSION / SOURCE-DERIVED OVERVIEW

Discussion summary

YOUR RESEARCHwierd pcm 1 behaviour

Leading reported evidence

Run but earthing ok

Suggestion or failed attempt

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

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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 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 · Original poster
testing does show slightly higher voltage when engine running but earthing ok
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wierd pcm 1 behaviour

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Leading evidence: 'Run but earthing ok' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Run but earthing ok' (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.

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1 matching discussions · 6 captured posts examined · 0 partial discussions

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Run would have

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 · Original poster
I'll pull the unit and do some tests, still don't understand how engine running would have that effect though.
Original post Read captured discussion
wierd pcm 1 behaviour

Test does show slightly higher voltage

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 · Original poster
testing does show slightly higher voltage when engine running but earthing ok
Original post Read captured discussion
wierd pcm 1 behaviour

Frequently discussed actions (3)

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

Run but earthing ok

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 · Original poster
testing does show slightly higher voltage when engine running but earthing ok
Original post Read captured discussion
wierd pcm 1 behaviour

Run would have

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 · Original poster
I'll pull the unit and do some tests, still don't understand how engine running would have that effect though.
Original post Read captured discussion
wierd pcm 1 behaviour

Test does show slightly higher voltage

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 · Original poster
testing does show slightly higher voltage when engine running but earthing ok
Original post Read captured discussion
wierd pcm 1 behaviour

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.

6 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.

911uk: 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: 20261026T052503Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources

POST 1 / ORIGINAL POSTEROriginal post

looking for advice/inspiration... 98 C2 with pcm 1 (8 bit), the one with cassette player owned over 8 years now and never had a problem (apart from somewhat out of date nav disc) recently, for no apparent reason - key in ignition - works perfectly key in position 2 - works perfectly start engine - screen still lit but - - buttons ( fm/cd/nav etc ) don't work no sound but a rythmic electric clicking from speakers switch off pcm and the clicking continues !! switch off engine and all is fine again possibilities - earthing? ignition switch? alternator/charging interference? beats me, help!

POST 2Original post

Difficult i'm afraid .. with engine running i would confirm there are a good earth , ignition feed and a permanent feed to the pcm .. i would do the same at the amplifier .. if voltage / earths are good at both then one of these units might require changing .

POST 3 / ORIGINAL POSTEROriginal post

thanks demort. I'll pull the unit and do some tests, still don't understand how engine running would have that effect though. regards ed

POST 4Original post

A few years ago I had the change the ignition unit (barrel) as it was causing me some issues , windows not going down when closing door etc.. At the time it seemed a common problem with 996s

POST 5Original post

Best guess is the voltage is higher when the car is running and the units no longer like this voltage :dont know:

POST 6 / ORIGINAL POSTEROriginal post

thanks have pulled the unit and unplugged/plugged all the connectors testing does show slightly higher voltage when engine running but earthing ok I think it's fubar after 24 years... time for an upgrade so - recommendations pls non most, non bose, just need basic dab/bluetooth/maps etc that doesn't look like something from startrek (but a porsche badge screen image would be nice!) regards ed

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