My 04 Suburban 175k mi. cranks but doesn't start. Happened before, towed it to the mechanic an said that it had a "loose wire" but didn't specify which one. It worked fine since November but its started again. It's got the same code as before too, P0178-"fuel composition sensor circuit low" an P0446- "EVAP system control circuit". What could it be??
So I had a mobile mechanic checkout my burban to fix the problem. Says its the fuel pump after all. He also recommended to change the fuel pressure regulator, $300 labor without the parts. After more than a week without a vehicle, I decided to swap out the pressure regulator ($130+ autozone) an turned on without a hiccup! I was trying to get in contact with him, but won't answer calls. Thanked him for the tip through a text an that was that.
Could be one code is setting the other to trip.
Chevrolet 1500: P0446 EVAP Vent Performance - YouTube
Check the three wire connector to the sensor for corrosion and tightness and especially the frame ground wire. If all are ok, I'd replace the sensor, Rock Auto $181.79.
