2006, Chevy, Trailblazer, LS, 4,2 L I-6. P0496

Question

'06 Chevy trailblazer w/ I-6 4.2L engine, LS, 4WD. 137,000 mi. Trouble code p0496 remains on, but also gas cap symbol illuminated temporarily for a few hours at a time on several days. Now replaced gas cap with new and wonder if it could have been the cause of check engine light? Or do I still need to give car to the mechanic and have him perform detailed test on EVAP system with the expensive monitor? Thanks.

Answer 1

P0496 Evaporative emission system flow during non purge

Checking the fuel cap is the first start for this EVAP code , when this code condition occurs its either the Purge valve that is stuck in the open position and is drawing unwanted vacuum in the fuel tank this is one scenerio and the second is the FTP (fuel tank pressure ) is reporting a false reading such as a vacuum when there is not.This is a simple test, what is needed is a scan tool that can read EVAP data and this will determin if it is registering the correct tank pressure in the fuel tank.  There also have been known condition where the EVAP purge solenoid has been stuck open and this usually gives a lean code bank condition. It is also possible this code condition was the fuel cap so give it a couple of days.