I have a 2004 Denali. Auto trans, 6L engine. I pulled a 18 ft. open car hauler and was pulling it up a hill small hill and it had no power. I could put the throttle to the floor and the engine would do nothing. The car is in great shape with 100,000 miles on it. What do you think is the problem?
The list is absolutely endless with the tiny little description you just posted.
Is the check engine light on?
By “do nothing” do you mean the engine was running but with little power? Or the engine stalled?
Was the engine overheating?
Did you have to have it towed in?
Has a mechanic looked at it? Do YOU have any diagnostic ability?
Help us out a bit so we can help you.