check engine light while towing

When the check engine light on your 2001 GMC Sierra 1500 blinks that generally means the computer has detected and engine misfire. The extra load may be causing a slight misfire - can you feel it? If so chances are replacing the spark plugs and wires may help. If you cannot feel the misfire diagnoses may be a bit more difficult. The first step would be to retrieve the fault codes stored in the engine control module.