Home > Technical (L405) > 2012 4.4SDV8 shutdown after five minutes of driving |
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cass Member Since: 12 Oct 2011 Location: northumberland Posts: 727 |
I’ve given up trying to apply logic to intermittent faults particularly electrical ones. Trying to second guess what the fault messages mean will make your head explode. If it were mine I’d start with a crank sensor. |
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12th Aug 2024 3:18pm |
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Quarryman Member Since: 20 Feb 2022 Location: Wiltshire Posts: 9 |
Thanks for the reply - yes I've been pulling my hair out with this one - luckily it just died while idling after I'd cleared all the faults and there were only a handful of new ones that appeared - I guess because it wasn't in gear and moving, faults like gearbox and abs didn't throw up so I can narrow it down a bit. I'll have a crawl around and check the crankshaft sensor plug next, the sensor itself looks like it's nearly impossible to get to, so might have to take it to someone with hands like Mr. Tickle... |
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12th Aug 2024 3:25pm |
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hmallett Member Since: 21 Jan 2024 Location: Mid-Wales Posts: 54 |
I would expect it to prevent the engine running at all. As I understand it everything electrical related to timing of the engine (such as the injectors) is timed from the crankshaft position sensor. Last edited by hmallett on 12th Aug 2024 9:19pm. Edited 1 time in total |
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12th Aug 2024 6:02pm |
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GraemeS Member Since: 06 Mar 2015 Location: Wagga area Posts: 2458 |
Monitor RPM while cranking with a diagnostic tool. Zero RPM or a momentary dropping to zero implies a failing crankshaft position sensor. |
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12th Aug 2024 8:41pm |
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Quarryman Member Since: 20 Feb 2022 Location: Wiltshire Posts: 9 |
Yes - I did try to find the values of the engine speed in the live data but couldn't see it initially however having the permanent fault now logged when the engine won't start points to the culprit. I'm just surprised that such a single point of failure can throw gearbox faults on the dash yet nowhere did the car complain of any engine fault. Only when it was stationary in park when the fault occurred could it be identified as the probable cause. I did assume that all sensors such as these have a backup nowadays - ie use the cam sensor to at least best guess the injection timing and get the engine running albeit in limp mode - I noticed some Discoveries of the same age were recalled due to the safety implications of this sensor failing, so I assume it is indeed a critical weak link. |
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13th Aug 2024 3:50am |
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kevinp Member Since: 28 Sep 2019 Location: Telford Posts: 1199 |
I had a similar issue on a Ford Explorer and it turned out to be the connector to the crankshaft sensor was dirty. If you can reach the sensor try pulling the connector off and on a few times. Worth a go. |
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13th Aug 2024 7:59am |
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Quarryman Member Since: 20 Feb 2022 Location: Wiltshire Posts: 9 |
Thanks for that - yes I will have a look at the plug connections at the weekend to see if they are loose or corroded, it definitely seems worse when the engine and weather is warm so could be just that. |
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13th Aug 2024 8:12am |
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GraemeS Member Since: 06 Mar 2015 Location: Wagga area Posts: 2458 |
Monitor rpm as a live value rather than go looking for the crankshaft position sensor to monitor which I doubt you'll find.
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13th Aug 2024 8:40am |
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Quarryman Member Since: 20 Feb 2022 Location: Wiltshire Posts: 9 |
The car is running fine now and the live value is fine when cold. The crank position diagnostics gives the P0036 failed error when the car is hot and won't start so what would be the benefit of checking the value when cranking? Surely the 'permanent' error code when it fails to start is the reason for not starting and it can only be the sensor or sensor wiring fault or am I missing something? |
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13th Aug 2024 8:49am |
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Quarryman Member Since: 20 Feb 2022 Location: Wiltshire Posts: 9 |
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13th Aug 2024 8:52am |
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GraemeS Member Since: 06 Mar 2015 Location: Wagga area Posts: 2458 |
Often there isn't a fault code so seeing a flat 0 line or dipping to 0 while cranking is evidence. |
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13th Aug 2024 8:56am |
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Quarryman Member Since: 20 Feb 2022 Location: Wiltshire Posts: 9 |
Oh thanks I see - well this definitely had the fault code stored as permanent after a failed start attempt so I assume it's not lying to me.
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13th Aug 2024 9:36am |
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