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dreaded P0442 code

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9.5K views 4 replies 3 participants last post by  txguy57  
T
#1 ·
The mechanics are stumped!
Have a 2011 Silverado 2500HD 6.0 4x4 Z71. Owned it about 2 years. Right after getting it I added a cold air intake, throttle body spacer, Flow master shorty dualled out after the cat. Gas mileage in the onboard info system showed about 11 mpg when I got it. After the upgrades it upped to 13's. About 15 months ago I got the gross leak code P0455. MPG dropped to 10's. Replace gas cap and the purge/soleniod (on top of engine). Things were ok for about 300 miles. coded out the P0442, Autozone warranteed the purge valve, all ok for about another 300 miles!
Over the last 15 months I have had the gas cap replaced with Autozone, Oreilly and now the OEM part. (lost count on # of caps) The purge solenoid is on about the 4th replacement, now an OEM part. The Evap canister has been replaced, replaced the fuel pump with the fuel tank pressure solenoid, replaced the fuel tank pressure solenoid again, the canister vent valve is replaced. the PCM was flashed but didn't fix anything and now has been replaced with a new OEM PCM and programmed. Mechanics have done a lot of this work. They have smoke tested the truck multiple times with no leaks detected. It has become a financial nightmare and of course frustrating to me and the mechanics. It has been suggested to change out the tank but for $1100 I am not anxious to do this. (the tank has a non serviceable vent??) From the posts I have read on here, this P0442 is a nightmare for everyone. Guess ethanol is the culprit but can't prove it. Oh, when I got the truck the vent line from the canister vent to up to the gas filler neck had been ran via some 5/8 heater hose to the firewall. When that vent was replaced the mechanics did away with that long redirect of the vent. Maybe I need to try that again. The filler neck was going to be replaced but the upon comparison with the new part the mechanic said there was nothing wrong with it so it was not replaced.
Summary: all EVAP related parts, (other than the hoses and the gas tank) and some of the electrical connectors to the solenoids have been replaced and some more than once.

So, I got on here to see if anyone had any great ideas on how to fix, once and for all, this P0442 issue we are all having.
 
#2 ·
Okay....this is what I found with my 2010.

The Vapor Cannister Vent Valve/Solenoid was causing the issue with P0442/P0455. Bought a GM gas cap...went away and came back soon after.

I noticed quite a few people installing a new vent valve/solenoid (near vapor cannister by rear tire) and running the vent line up to the tranny like stock. I dont think the 2500 was set up this way BUT i think you could still do this as I suspect the vent/solenoid installed in 2011 Silverado 2500 6.0L on your truck is the same one that came original to my truck (looking at RockAuto.com pics of OE AC Delco vent valve/solenoid for 2011 2500 6.0L)

So if you go to Rockauto.com and go to 2011, Exhaust and Emissions, Vapor Cannister Vent Valve/Solenoid you will see 2 AC Delco options for your truck. Verify you have one of these installed because they should have a vent line running up to tranny.
PN 2142330
PN 2142331 (with a heart as preferred)

Both of those have a hose for vent...BUT they are the exact same ones giving most people problems and look exactly like my OE vent/solenoid on my 2010 5.3L. On rock auto go to year 2010 silverado 1500 5.3L , Exhaust and Emissions, Vapor Cannister Vent Valve/solenoid and look at PN 23103351. That vent valve/solenoid is larger and vents better than the OE unit that came with both of our trucks which are smaller. It doesn't have the vent line so you wil need to purchase some hose to run it up along the frame to the top of the tranny. What I cant be sure of is the connector...if it will plug into your harness or you will have to purchase the pigtail as mentiond on rockauto.com for PN 23103351. (adapter harness 19257603)
 
T
#4 ·
yes, gas mileage drops just before the code light comes on and continues to drop a bit. The worst avg was 9.6 while the CEL was on. If I clear the code the mpg gets back up to 12.7. It can hold the 12.7 and creeps up to the low 13's depending on where I'm at and how hard I'm pushing it. As long as the diagnostic doesn't trip the code the mileage stays steady
 
T
#5 ·
7-8-19 UPDATE
after all the money and frustrations it has been discovered that a fitting in a hose that is behind the intake manifold and over the trans was just loose enough to code out the truck but not enough of a leak for multiple leak tests to discover it. If finally exposed itself when I had the trans replaced. I have not had this code pop in 9 months and a whole lot of driven miles. So, I guess if anyone has this issue, have the mechanic move, twist and pull on ALL the lines and fittings. Could save you lots of time, frustration and $$.
 
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