I took my suburban to pull the codes for service engine soon light
They said it is a 0440 code.I replaced the gas cap,any other suggestions.Is this a serious thing or can I still drive it.Thanks Jimbo

 

IF it was the gas cap it will soon go away, Its likely one of the common issues in these trucks with regard to evap control. Do some searching. You should get the code erased first, see if it comes up.

 

p0440 is most likely a large evap system leak. most common causes are a failed evap vent solenoid that will not seal the system during evap leak testing.

it will not leave you stranded. it is an emission control system that stops unburned fuel from escaping into the atmosphere...creating air pollution. it will fail any state emission testing.

proper diagnosis will involved sealing the evap system with a scan tool having a smoke tester fill the system. the leak is pinpointed by finding smoke existing the sealed system... or you can keep guessing and replace parts.