P0455 & P0442 ECU Fault Log H3 Hummer


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About a year ago my ECU light came on in my H3 Hummer, noticeably after some fun off-road. I grab my cheap Chinese OBD-II to Blue Tooth scanner from eBay and open the Android application “Torque“. The scanner had no problem grabbing the code and I was able to see the error report in the computer.

Fault log report generated by Torque for Android

Vehicle VIN: 5GTDN136X68227871
Vehicle Manufacturer: Unknown
Vehicle Calibration ID: 12606370
Current Fault Log
P0455: Evaporative Emission Control System Leak Detected (gross leak, check fuel cap, piping etc)
P0442: Evaporative Emission Control System Leak Detected (small leak)
Pending Fault Log
ECU reports no pending faults
Historic Fault Log
ECU reports no historic faults
Other discovered fault codes
(possibly pending, current or manufacturer specific)
ECU reports no other fault codes logged
End of report.

After some research, I had decided one of two parts had to be giving the ECU the errors, the 20907779 GM Original Equipment Vapor Canister Vent Hose or the 25827646 Fuel Tank Cap. I checked the Fuel Tank Cap over and it looked in great condition, must be the vent hose. Although I ended up buying both parts because at this point I’m tired of having the engine light on. The day when the parts got delivered to my door, I didn’t have time to install the Vapor Canister Vent Hose. But I was able to quickly put the new Fuel Tank Cap on. Got in the Hummer and drove off. Curiosity got the best of me on this long drive, and plug that handy application “Torque” in and reset the ECU error code on the fly to see if it really is just the Fuel Tank Cap.

As it turns out, after driving about 2,000 miles the engine light came back on. Which really left me disappointed because I had returned the ACDelco 20907779 GM Original Equipment Vapor Canister Vent Hose to Amazon.com. I reordered the part but found out that a little adapter wire is now needed to use this version Vapor Vent Hose. You’ll need to order ACDelco 19257603 GM Original Equipment Evaporative Emissions Canister Vent Valve Solenoid Jumper Wiring Harness so that you can connect everything without having to splice wires.


  1. I like your website and have read your posts on the different Hummer-specific forums. Keep up the great work you’re doing.
    I also have a 2006 H3. I have 137000 miles on mine. My engine light just came on for the vent valve solenoid as well. I will be ordering the HVAC panel control bulbs very soon from your site as two of the three are burned out as well as the driver side armrest window controls. Thanks again for supporting these awesome vehicles.

    1. Schwarttzy Avatar

      Thanks for the compliments! Keep an eye out for the new projects I’ve got planned to 2018.

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