Wiring issue - Crank, No Start

rockola1971 said:

Terminal Pinout Ignition Coil
86 (Relay coil +)
85 (relay coil -)
30 Power source for load
87 Device (load)

Firstly your 11.5v readings should be well above 12v, along the lines of 12.6v + so charge that battery. Low battery could cause your ignition relay to chatter. Terminals 85 and 87 will read 0v since terminal 85 is ground and 87 because you are holding the relay in your hand which passes 12v to it when relay is energized closed. So do a resistance measurement to ground from terminal 85 to verify it has a good ground. Once battery is charged up, test PCM1 fuse for 12v with someone cranking engine over. If good then you could have a broken wire between fuse block PCM1 and PCM C1 Plug or you could have something going on at the PCM C1 plug at the PCM terminal 19 Pink Wire. Inspect for rodent damage, corrosion or pushed/broken/corroded terminal within C1 plug.

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BoostedC230 said:

It was IGN 1 relay ground!!! I ran a temporary ground and I got the 12 volts when cranking!!!! Started it up and it's running great! Thank you so much. I'm so dang excited

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rockola1971 said:

You are very welcome. Get that ground fixed and back to factory original spec.

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rockola1971 said:

You are very welcome. Get that ground fixed and back to factory original spec.

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Schojo said:

I’m having electric issues extremely similar to OP in my 2004 5.8L 2WD Yukon. We changed the heads and o2 sensor and crankshaft sensor and it will just die randomly while driving. We checked and cleaned the connection for the crankshaft sensor. We haven’t checked the grounds yet, I’m not exactly sure where they’re all located. It will run fine for a few a days and then boom randomly will completely die and not turn back over or if it does it’s very short. Almost exact scenario as OP just a diff trim

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