7 captured repliesPartial discussion capture · Source accounts, not a confirmed diagnosis
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Discussion summary
YOUR RESEARCH996 Crank Position Sensor replacement info
Reported or suspected cause
low voltage while driving and not starting
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No successful repair reported for this finding.
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Reported cause · Original poster
First problem was low voltage while driving and not starting when hot - (already collected parts to replace the starter/alternator cable, alternator regulator, drive belt etc) but then it just won't start at all from cold.
Leading evidence: 'low voltage while driving and not starting' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'low voltage while driving and not starting' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Check fuses' (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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Discussions that performed work without a confirmed outcome
1
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Performed · outcome unconfirmed · Original poster
Yep, as recommended used a 5mm hex and ratchet, came out easily.
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Suspected cause · Original poster
No movement of tach - that was one of the main symptoms that made me suspect CPS.
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Replace starter/alternator cable, alternator regulator, drive belt etc)
No successful repair reported for this finding.
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Suggestion · Original poster
First problem was low voltage while driving and not starting when hot - (already collected parts to replace the starter/alternator cable, alternator regulator, drive belt etc) but then it just won't start at all from cold.
These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.
low voltage while driving and not starting
No successful repair reported for this finding.
1
Identified cause
0
Suspected cause
0
Reported fixes
Read evidence and context
Discussions that report identifying 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.
Reported cause · Original poster
First problem was low voltage while driving and not starting when hot - (already collected parts to replace the starter/alternator cable, alternator regulator, drive belt etc) but then it just won't start at all from cold.
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.
7 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Porsche Forum Australia: 1 discussions
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Generation: 20261026T063944Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
Hi guys
Had my 996 hibernating in the garage for about a month now as it refuses to start. First problem was low voltage while driving and not starting when hot - (already collected parts to replace the starter/alternator cable, alternator regulator, drive belt etc) but then it just won't start at all from cold.
After a bit of research I reckon it would be the crank position sensor, so had a wait a while for one to arrive from overseas. Has anyone replaced the CPS themselves on a 996? Been searching for a good DIY guide but can't find one - from what I've read, jack up the car, remove rear (left?) wheel, unbolt a 5mm hex holding in the CPS and unclip harness, then install new one.
Yes I have done it - its pretty straightforward. I found tapping a hex bit into the retaining bolt and using a 1/4" rachet helped to get it out more easily than using a normal elbow allen key.
Also take a good look / photo of the position of the plugs and clips before unplugging the old cable - its easy to forget where it all is routed when the old one is hauled out.
Not sure it will fix the problem though - but its worth a try. Have you checked all your fuses? Could be something as simple as a popped starter circuit fuse.
Good advice on checking fuses - will do that before I break out the toolbox! Other tips also good too, thanks
Will try and take a whole bunch of photos etc and write it up in the diy forum.
Have you considered a cheap OBDII tester. It can show if the ECU has emission related errors and also show the RPM which is from the crank position sensor. If the cranking RPM is plausible then the chances are there is nothing wrong with the sensor.
Try these before you loosen the tool roll:
1) Make sure your battery is up to full charge - you want to see 12.6v @ the terminals.
2) Can you hear the fuel pump run when you switch on the ignition? It stops after about 3-4 seconds as it pressurises the system.
3) When you crank the starter, does the tach move slightly? If it moves its getting the signal from the CPS - if it remains static, your CPS is probably faulty.
Thanks everyone for helpful tips!
Yep, as recommended used a 5mm hex and ratchet, came out easily.
Took photos, still managed to install the bracket with the variocam cable trapped behind it. Swore, removed and reinstalled it properly.
Checked fuses - all seemed good.
I've got an autel, didn't record any new codes when the car wouldn't start. Didn't even think to try a realtime monitoring of RPM - very good tip that one though.
Brand new battery 2 months ago, and regularly on a ctek. Multimeter read over 12.6
Maybe my ears are bad, I can never hear the fuel pump priming in this car (I hear is in my other cars though!)
No movement of tach - that was one of the main symptoms that made me suspect CPS.
Anyway, did a DIY writeup in case anyone else needs some pointers - thanks again guys
tim
