hazard light flash with turn signal on 2004 Chevrolet Avalanche 1500

hazard light flashes when left turn signal is applied. Does not always happen

Intermittent problems with the turn signals can sometimes be attributed to a computer problem. I had something similar happen to me--completely intermittent and strange. I took my car in to the shop, and the onboard computer had every failure cataloged. They had to replace the turn signal module.
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check combination switch