Message comes up P440 - 1999 Chevrolet Silverado 1500

You need a Catalytic converter and possibly a Evap. cannister

Check the distributor cap for cracks.

EECS.pruge flow.

evaporative emission system, check all vacuum hoses for cracks or leaks. egr valve will cause this, most common problem = GAS CAP. after you replace the cap, or fix any leaks, remove the negitive cable from battery for 20 seconds to reset. Light should not come on till something else bad happens.

the code ur are getting on your envoy is a emiision problem first you could try a new gas cap its a known problem in setting this code ...hope this helps

Answered the other similar question

under the rear of the vehicle under the trunk

thats a evap code should not turn the car off you are heaving some other issue

The P440 means that Evaporative Emission Control System.
_______________
car code scanner

Most likely gas cap but sometimes a hose off of the airfilter box comes off.