u/Exotic-Cell-1754

How did you guys get past the point of three throws - three catches (up up catch up catch catch)

I'm hoping someone with more electrical diagnostic experience can point me in the right direction.

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Vehicle is a 2005 Buick Rendezvous. The engine will not crank with the key, but if I manually jump the crank relay (or squeeze the exposed relay while someone turns the key), the starter engages immediately and the vehicle starts. Once it's running, it drives perfectly with no issues at all.

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Here's what I've replaced or tested so far:

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New ignition switch

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New starter

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New OEM battery cables from Buick

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New 800 CCA battery

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Swapped in another underhood fuse box from a junkyard for testing (same exact symptoms)

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I've also checked the ignition switch wiring. I'm not a mechanic, but I verified that the wiring harness coming out of the ignition switch appears to be putting out the proper voltages when the key is turned.

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At this point I'm wondering:

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Could the PCM/BCM be preventing the crank relay from being grounded?

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Is there a common failure point in the crank relay control circuit on these?

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Could Passlock cause this even though the engine runs perfectly once I manually get it to crank?

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Are there any grounds or connectors that commonly fail on these?

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Any advice on what to test next would be greatly appreciated. I'm trying to diagnose this the right way instead of continuing to throw parts at it.

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Thanks!

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Any advice that results in the car being fixed can have 20 bucks 😅

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I'm making a video detailing what it's like to work for 7/11. Hoping to get a few phone interviews from employees; if you're interested comment below and we can figure out a time and calling application that works best for you