Customer Says: "IT'S BROKEN!"...But IS IT? ('07 Chevy Equinox: Transmission LIMP Mode P2534)

Customer towed in his 2007 Chevy Equinox V6 that is apparently stuck in Transmission LIMP MODE after a recent head gasket job.

The car has been off the road for a YEAR.

It starts and runs, but apparently the transmission doesn't shift gears.

I take it on a test drive and everything seems FINE!

There are some codes stored in HISTORY, including

P2534 - Ignition Low Voltage.

So is this an INTERMITTENT problem?? I'm confused...

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