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Discussion Starter · #1 ·
:grrrrrr: check engine light has been on since last christmas- shows code "small evap leak". I have replaced the cap w/ a new gm per VIN#,
solinoid vent valve, & the system was "fogged" or "smoked" ( & my wallet vacuumed!) any further things to check - has anyone else a problem.
I'm about to roll 100k miles.
 

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I haven't had this issue crop up yet. The smoke test is valuable if it locates the leak. Check the gas cap and filler pipe, and underhood hoses.

From: automotiveforums.com
Proper testing of the EVAP system will lead to the root cause.
The EVAP small leak test applies vacuum to the evaporative emission (EVAP) system and monitors vacuum decay. The powertrain control module (PCM) monitors the fuel tank pressure (FTP) sensor signal to determine the vacuum decay rate. At an appropriate time, the PCM turns the EVAP canister purge valve ON (open) and the EVAP vent valve ON (closed). This allows the engine to draw a vacuum on the EVAP system. At a calibrated time, or vacuum level, the PCM turns the purge valve OFF (closed), sealing the system, and monitors the FTP sensor input in order to determine EVAP system vacuum decay. If the system detects a leak larger than a calibrated amount DTC P0442 will set.
The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
inspect for leaks in the following locations:
The EVAP system purge pipe.
The EVAP vapor pipe.
The EVAP vent hose/pipe.
The fuel fill pipe/hose and fuel fill cap.
The EVAP canister.
The EVAP canister vent valve.
The EVAP canister purge valve.
The fuel sender assembly and/or seal.
The FTP sensor seal.
The fill limiter vent valve, pressure relief valve, rollover valves, and fuel tank.
 

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Discussion Starter · #3 ·
evap problem

thanks! I have a feeling I'm going to have to spend a Sat looking at it myself - as others haven't been able to @ 70 $ / hr!
I now have a new code after the last one was cleared for " small evap leak"
now the code is for "evap malfunction" after 111 miles. I wrote the # down, but now I can't find it- 4 something.
today I noticed the compressor ran a lot. found a rear shock leaking - there goes another 400 bucks! (autoride system - another great money sucking idea)
 

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Discussion Starter · #4 ·
well - fixed the shocks & compressor myself - about 200 for the compressor & another 200 for the shocks. I think the truck is old enought that less expensive - oem parts can be found w/ patience! the evap issue is still a problem. got a sticker in Jan by cancelling the code, driving it on a 300 mile trip , keeping it outside in the cold- yahoo got a sticker! now its warmer & I can smell gas - time to fix it. Maybe I can find the leak w/ a match!
 
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