Dying starter or more grounds?

mudder said:

This looks like a brownout condition that is resetting the ECM's starter relay bypass timer. The ECM waits several seconds for the IMA to start the car, but after that it connects the starter bypass relay. When that relay suddenly energizes the starter - a huge current inrush event - the 12 volt rails drops below 5.7 volts, causing the ECM to brownout, which causes the same relay to open back up, and then the ECM starts the timer again.

So this is definitely a brownout due to starter current demand. Knowing what I do about the G1, it's probably a grounding issue. If not, it's possible the starter has a dead spot in it, which causes the starter to pull way more current than the battery can deliver.

It is not the positive starter lead or solenoid.

If random jiggling doesn't work, get a digital volt meter that has a "minimum voltage" logger (e.g. Fluke 110, or just use an oscilloscope). Connect that to the cigarette lighter (since it's on the same wire harness going to the ECM). See if the voltage drops below ~9 volts while starting.

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mudder said:

turbo, your additional data almost certainly confirms my previous diagnosis: bad grounds (or less likely bad positive to cabin wire harness). Next steps:

1: Connect volt meter's positive lead to cigarette lighter, and negative lead to battery minus. What minimum voltage do you see when starting? If really low, then the positive lead is damaged somewhere from battery to cabin fuse block.

2: Connect volt meter's negative lead to cigarette lighter, and positive lead to battery plus. What minimum voltage do you see when starting? If really low, then the ground straps are hosed.

Happy tinkering.

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