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Random shutdown problem...

Old Oct 6, 2018 | 12:42 PM
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Default Random shutdown problem...

Hi guys, 2005 M6,
I've got a random shutdown problem and not sure where to go with diagnosis, i'm thinking cam sensor because of Tech II readings but would like some guidance please.
After recording ignition data with Tech II and reviewing the data, i noticed that the CMP sync counter was incrementing from 0 to 255 (not sure if that is normal?) but the CMP sensor reading was pegged at 1040 RPM and not fluctuating.
The CRK sensor and sync counter appear normal, CRK sensor matching vehicle RPM.
But then suddenly the CMP sensor started to read for a few seconds and then froze again and at the same time the spark went from 13 deg down to 0 and -5.
The spark then went back upto 13 deg but CMP still froze.
Any advice on where to look next?
Cheers
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Old Oct 7, 2018 | 11:39 AM
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Originally Posted by mazzerman
Hi guys, 2005 M6,
I've got a random shutdown problem and not sure where to go with diagnosis, i'm thinking cam sensor because of Tech II readings but would like some guidance please.
After recording ignition data with Tech II and reviewing the data, i noticed that the CMP sync counter was incrementing from 0 to 255 (not sure if that is normal?) but the CMP sensor reading was pegged at 1040 RPM and not fluctuating.
The CRK sensor and sync counter appear normal, CRK sensor matching vehicle RPM.
But then suddenly the CMP sensor started to read for a few seconds and then froze again and at the same time the spark went from 13 deg down to 0 and -5.
The spark then went back upto 13 deg but CMP still froze.
Any advice on where to look next?
Cheers
Still having issues my friend ??...ever find the ground for the coils ??...absolutely a bad CMP sensor can cause the engine to shut down randomly...does it happen while you are driving or a idle ??...one of it's functions is to control engine timing...I believe you said you have a scope...did you scope the cam signal ??...it produces a 0-12 volt square wave and you'll see it on the scope..(my LS1 CMP waveform pictured) ...Just make sure it you see 12 volts and then gets pulled down to ground....you don't want to see say 2-10 volts !!...but it does sound like a cam sensor !!

Last edited by C5 Diag; Oct 9, 2018 at 08:25 AM. Reason: add waveform
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Old Oct 7, 2018 | 03:20 PM
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Hi mate.
Yeah got it started ok after our work over the past couple of weeks but just now got to iron out a random shutdown.
The cam sensor was looking a bit strange on the Tech II, got solid CRK signal but intermittent CAM signal.
I already had a new CAM sensor so went ahead and fitted it today, (its a crazy location, i had to remove a ton of stuff) but it seems to have made a difference. on the scan tool it stays static around 1050 RPM but then when i increase throttle it matches RPM on Engine speed and CRK sensor so looks good.
I let the car idle for 20 minutes and it stayed running, just need to take it for a run tomorrow and hope it doesnt cut out on me, its always a worry incase it does it in a dangerous place.
But gotta bite the bullet and hope for the best.
i will use the scope if i have any issues.
It was cutting out on idle BTW.
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Old Oct 7, 2018 | 03:40 PM
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Originally Posted by mazzerman
Hi mate.
Yeah got it started ok after our work over the past couple of weeks but just now got to iron out a random shutdown.
The cam sensor was looking a bit strange on the Tech II, got solid CRK signal but intermittent CAM signal.
I already had a new CAM sensor so went ahead and fitted it today, (its a crazy location, i had to remove a ton of stuff) but it seems to have made a difference. on the scan tool it stays static around 1050 RPM but then when i increase throttle it matches RPM on Engine speed and CRK sensor so looks good.
I let the car idle for 20 minutes and it stayed running, just need to take it for a run tomorrow and hope it doesnt cut out on me, its always a worry incase it does it in a dangerous place.
But gotta bite the bullet and hope for the best.
i will use the scope if i have any issues.
It was cutting out on idle BTW.
Is yours on the back on the intake manifold like the C5 ??...so you have a new cam sensor fitted today...is it an OEM or aftermarket ??...any "sensor" on the Corvettes I'd stay away from aftermarket ones...i.e Dorman etc...my Autel shows a CMP signal low to high and high to low...it just counts up I think to 65,000 or something like that...I just had a P1518 pop up on mine last week and think it's a bad ignition switch...99.9% sure...I have a switch on order. car would not crank and had a low voltage on the DIC looking at me...I know my battery is fine...cycled the ignition switch a few times quickly and it started...my quickest diagnosis...LOL !!!
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Old Oct 7, 2018 | 03:53 PM
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No, on the C6 it's tucked at the back next to the harmonic balancer and has a shield around it and it was incredibly difficult to get to with the power steering reservoir and coolant pipes in the way.
I got an AC Delco OEM cam sensor, i also have an ignition switch on order and should be here on Monday so gonna fit it as a precaution as i think mine is hit and miss on the starting and going between ACC etc.
Good diagnosis call on yours.
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Old Oct 7, 2018 | 03:56 PM
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Originally Posted by mazzerman
No, on the C6 it's tucked at the back next to the harmonic balancer and has a shield around it and it was incredibly difficult to get to with the power steering reservoir and coolant pipes in the way.
I got an AC Delco OEM cam sensor, i also have an ignition switch on order and should be here on Monday so gonna fit it as a precaution as i think mine is hit and miss on the starting and going between ACC etc.
Good diagnosis call on yours.
Good show !!...hopefully we will get both our issues resolved and in good nick !!...I also ordered 8 AC Delco coils too and they will be coming next week too !!

Last edited by C5 Diag; Oct 7, 2018 at 03:56 PM.
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Old Oct 7, 2018 | 04:03 PM
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Next for me, i would like to get a coil/injector harness, the heat has started to harden all the cables.
Yeah i'm sure we will both get them sorted soon.
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Old Oct 7, 2018 | 05:28 PM
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[QUOTE=mazzerman;1598118098]Next for me, i would like to get a coil/injector harness, the heat has started to harden all the cables.
Yeah i'm sure we will both get them sorted soon. [/QUOTE

Did you ever find that ground for the coils on the bottom of the car ??
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Old Oct 8, 2018 | 03:54 AM
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Yeah i found it, and it looked OK but cleaned it up anyway, but all along i think it was a failing cam sensor, but need to test the theory before i can relax...
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