'02 Impala: No Start, Then Brake Pedal Start

[Colt Hero]

148k miles. 1LT model.

Wife got in the Impala this past weekend and said the car wouldn't start. I told her to make sure she had the transmission selector in PARK because she'd made that mistake once before. 2nd try (verifying PARK), same thing ... no start. I subsequently tried with the key and sure enough ... no start. Lights came on on the the dash, but just a faint noise (not really a click, sort of a "poof") and nothing.

But then I stepped on the brake pedal, turned the key, and it started !!

Later that day, for a sanity check, I leaned into the car sideways on the driver's seat and turned the key (no brake pedal), and the car started (like it always used to .... I was starting to think you needed your foot on the brake to start the car, but this has never been the case with this car).

Any ideas as to what happened here? There was no SECURITY message (which we've seen before as a reason for a 'no-start' condition, but this hasn't happened in several years now, and had only happened a couple of times EVER). Also, the battery looked OK (although it IS 4 years old now). The car hasn't been getting driven as much since I bought the 2011 Equinox in January. Just weekends, but usually every weekend and I had just run it on the Sunday 6 days previous without any problems.

[maxwedge]

Check the grounds and battery cables.