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Battery Light comes on while driving my GMC

I have a 2000 GMC Sierra 5.3 V8. While driving the battery light,airbag light,and seatbelt light all flash at the same time. The spedometer also drops to zero. After a few seconds the lights go off and driving is not affected. The battery cables are tight and secure. What could cause this?

Have you checked for service bulletins issued by the manufacture? this is the first step (perhaps verifying the complaint is the first step in some peoples minds) in the repair strategy.

It sounds like there may be a common power source to those areas and there is a faulty connection with the power to those areas. Checking a wiring diagram would verify that.

I began at my local auto shop thinking they could use a diagnostic tool to determine the problem. Their response, (and the response from another), was that until something failed the diagnostic wouldn’t show any issues. Should I strong-arm my mechanic into plugging it in or am I at the mercy of the upcoming failure?

I don’t hold you or any of the general public in contempt when they are confused or have misconception about what the vehicles on-board diagnostics are mandated to do and the extra features that some manufactures add to their on-board diagnostic systems, but the public has it way wrong.

On-board diagnostics are mandated to keep watch on emissions related systems (spark plugs and wires fit under the umbrella of “emissions related systems”, just for example). Some manufactures add enhancements to the onboard diagnostics to help trouble shoot systems that are related to the “body” of the car like lighting, ABS, steering,stability control. No manufactures on board diagnostic system will give answers or trouble shooting hints above the most basic level for solving the concern you are having with your GMC.

A mechanic will have to revert back to the “old days” and use his ,eyes,ears, hands, nose, and experience and training to find the fault in your vehicle.

I myself was presented a 1998 S-Blazer whose owner claimed the dash lights would all come on at various times and the speedo and tach needles would swing widly (also the battery and temp gagues) this vehicle was presented to me under warranty status. I inspected the vehicle under the .6hr time allowed by GM and no trouble was found and I could not duplicate the concern. I sent the customer away. customer returned from vacation with a video, Oh great I thought, vacation video, well it seems the customer was filming out the window when the cars gagues went nuts and now they had their proof. I ended up putting a complete under the hood electrical harness in that S-Blazer, never saw the customer again, I don’t know if that was a good or bad sign.

Why is everyone making this so complicated. Low system voltage could be causing the problem.

Start by having the charging system checked.