08 Tahoe 5.3 Flex AFM - no spark on #6
November 14th, 2020, 7:08 PM
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08 Tahoe 5.3 Flex AFM - no spark on #6
No spark at all on #6, confirmed with obd2 tool, timing light. Swapping coils, plugs, and wires produces no effect, cylinder #6 still no spark. Spark confirmed on all other cylinders. Fuel good (wet at least).
Only codes are p0306 and a commanded abs system " disable due to engine performance". No other tests failing, ecu seems to be sending the signal fine.
Wire tracing, continuity testing, and short to ground testing all produce good results, no problems there.
Got a new coil pigtail, wired in my own 12v, ground, signal, and signal ground ... No change.
Disconnected the cylinder #4's coil, plugged them in "backwards" (so the ecm is firing #6 thinking it is firing #4 and vise versa), and still no spark on #6 (even though it should be firing when #4 fires), and #6's coil plug is firing #4
So I'm confident this isn't a wire or ecu problem.
Replaced cam sensor (it's in the dealer diagnostic chain). No change.
Any ideas?
Only codes are p0306 and a commanded abs system " disable due to engine performance". No other tests failing, ecu seems to be sending the signal fine.
Wire tracing, continuity testing, and short to ground testing all produce good results, no problems there.
Got a new coil pigtail, wired in my own 12v, ground, signal, and signal ground ... No change.
Disconnected the cylinder #4's coil, plugged them in "backwards" (so the ecm is firing #6 thinking it is firing #4 and vise versa), and still no spark on #6 (even though it should be firing when #4 fires), and #6's coil plug is firing #4
So I'm confident this isn't a wire or ecu problem.
Replaced cam sensor (it's in the dealer diagnostic chain). No change.
Any ideas?
Last edited by Engineerium; November 14th, 2020 at 7:10 PM.
November 15th, 2020, 11:22 AM
#2
Welcome to the forum from Oregon.
Based on all your previous attempts and swapping and wiring testing I am gonna say that the ECM is failed causing no signal to cylinder #6 to fire the coil. This says it better: Replace the ECM for a bad circuit that powers the fuel injector or coil for number 6.
I would also do a complete compression test, I never do just one or two cylinders, especially on an AFM engine. Make sure all plugs are out when you do the compression test.
Based on all your previous attempts and swapping and wiring testing I am gonna say that the ECM is failed causing no signal to cylinder #6 to fire the coil. This says it better: Replace the ECM for a bad circuit that powers the fuel injector or coil for number 6.
I would also do a complete compression test, I never do just one or two cylinders, especially on an AFM engine. Make sure all plugs are out when you do the compression test.
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