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Thread: C6 Z06 LS7 - full electrical power cut and stall. VCM diagnostics?

  1. #1
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    C6 Z06 LS7 - full electrical power cut and stall. VCM diagnostics?

    Hi all - Just got my 468ci ls7 back in my Z06 and am having an intermittent (but regular) engine cut-out when driving, full electrical cut. Dash VATS / Key icon illuminates followed by check engine light etc. Engine drops back to 0 and stalls when clutch pushed in.

    Q - What diagnostics are available in VCMsuite, particularly crank and cam sensor output? I don't have a TECH2 and I`m not in the USA!

    I`m aware of the DTC readout of course and nothing is reported here following the cut. I am also checking wiring, earths etc

    Thanks.

  2. #2
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    Just for anyone else with similar issue.

    It was the earth connection on the block, starter side. The bolt was finger tight, so looked fine when viewed from above. But when i tightened it correctly issue was resolved.

  3. #3
    Advanced Tuner TheMechanic's Avatar
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    Quote Originally Posted by Sub8 View Post
    Hi all - Just got my 468ci ls7 back in my Z06 and am having an intermittent (but regular) engine cut-out when driving, full electrical cut. Dash VATS / Key icon illuminates followed by check engine light etc. Engine drops back to 0 and stalls when clutch pushed in.

    Q - What diagnostics are available in VCMsuite, particularly crank and cam sensor output? I don't have a TECH2 and I`m not in the USA!

    I`m aware of the DTC readout of course and nothing is reported here following the cut. I am also checking wiring, earths etc

    Thanks.
    Most of the time if you have a grounding issue you will get no codes and a stalling/engine shutoff condition. If it is a power supply side issue you will get random multiple codes that make no sense. This is a VERY generic answer. As for scan tool if you can't seem to find the problem it's time to look at the power and grounds that should have been checked before you started the diagnosis.

  4. #4
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    Quote Originally Posted by TheMechanic View Post
    Most of the time if you have a grounding issue you will get no codes and a stalling/engine shutoff condition. If it is a power supply side issue you will get random multiple codes that make no sense. This is a VERY generic answer. As for scan tool if you can't seem to find the problem it's time to look at the power and grounds that should have been checked before you started the diagnosis.
    Yup for sure. My only excuse is that I could see the earth wires. I was still surprised that finger tight vs spanner tight had such a dramatic effect. Not like it was hanging loose...

  5. #5
    Advanced Tuner TheMechanic's Avatar
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    I had the exact issue on a tow in. First thing I do on the no start is power and ground. I have a high beam sealed headlight that I use as a test light for shorts, grounds and stuff that will have a good amount of current. It can take a few amps so if you put it on bat + and on the ground wire if it doesn't get a good light you know it is a bad ground circuit. Same thing, on the left side of the block the grounds were there but the bolt wasn't tight. Tighten it up and charge them.

  6. #6
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    'Check the grounds' is kinda a code that really means 'ensure that the wire is intact from point to point, and the fastener is present and tight enough by checking it with some sort of tool, and that the location the ground wire is attached to has good continuity to B-'.

    Same thing when a pro says 'checked all fuses' - that really means they made sure the fuses were all physically intact, and that all the fuses were where they were supposed to be with none missing, and that the hot-at-all-times fuses are truly hot-at-all-times and the switched IGN fuses are hot with IGN on, etc.