P0442 OBDII DTC - again

[jocko]

Good evening folks - normally hang out on the 60-66 pages herein, but also drive a 2001 Z71. Have the dreaded recurring P0442 with check eng light MIL. Gas cap and seal appears to be fine - all lines to/from canister seem fine - are there any threads on here that hav discussed the most likely fixes of this nuisance code? I've got an Actron scanner - check the code every time it pops and reset it, but it sure is getting old. Appreciate your help.
Jocko

[clinebarger]

Replace the gas cap or have it tested at a smog/inspection station first.

[bighaas79]

best way to find evap leaks is to use a smoke machine.

[mbgmike]

Have you checked the cannister vent valve by the fuel tank. Its pretty common to have a leak in them.

A smoke machine is a big help. You can run air pressure through the lines and listen also.

Also check the canister for a tiny crack

[pmpislander]

while mine is a 99 and a 4.3 im having the same problem and cant seem to find it. what is the safe amount of air pressure to run through theses lines to look for leaks?

[truckdude239]

umm less then 3 psi

[BACKYARD88]

P0442 is a small leak. If it's not the fuel cap the next most common thing is the canister vent solenoid not sealing completely. Sometimes a P0442 can be hard to find since the system can detect such a small pressure change.