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Wanted to pose a question, first-the situation:
2006 Trailblazer I6 engine.
Previous owner told me check engine light was on and it was difficult to fill with gas. Bought it anyway as it ran well and I got a reasonably good price.
So, I did a little research, found that the 0455 code( EVAP large leak) is rather common with this vehicle. I replaced the vent solenoid by the engine block and cleared the code. The P0455 came back about 3 days later, however I never had any problems putting gas in after that.
Got sidetracked with house stuff, kid/school/sports stuff…life for a few months. Finally in July, I replaced the purge solenoid (by the gas tank). Cleared the code again.
About two days later, the check engine light comes on again. I check it, expecting to see P0455 again but it’s not…it’s P0171 (Bank 1 too lean). This code sets, then goes away on it’s own…then returns apparently randomly.
We’re now at almost four weeks since I resolved the EVAP issue-no more leak codes since then.
I have another thread going about troubleshooting the 0171, but my question for this post is this:
Is it just coincidence that I never got a P0171 code until AFTER I finally resolved the P0455? Or could it be that now that the EVAP system is sealing and purging like it should that I now have a lean condition?
Thanks for reading…several people on this board have already been very helpful and I appreciate it!
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what’s the solution for that? is this an indication to get the PCM reflashed/updated at the dealer?
I’d rather fall into a snake pit than go to the local dealership, but if I gotta…guess I gotta.There was a PCM update on the issue you’re having, but….This is a video I found in the internet of the same problem I had years ago on a Trailblazer during the warranty period. The issue with it was a malfunctioning air solenoid control valve in the vehicle’s secondary air injection system.
My thinking is the PCM maybe opening solenoid control valve and not setting a code. Hopefully this video will help you understand how the system works for further diagnosis. http://www.wellsve.com/video_chevrolet_trailblazer_diagnostics.html
You may have to attach a DVM on the solenoid control valve, air pump or PCM circuit to see if the system is working when it should.
I saw that video a while back, I took a chance and changed that solenoid (didn’t help). If I understand you though,if the PCM is commanding the solenoid open in my case, then that could be the reason it’s running lean. solenoid is working but getting bad instructions from the PCM.
solenoid is working but getting bad instructions from the PCM
Correct, but you have to verify that the solenoid is letting air into the exhaust. The only way I know how to monitor the solenoid is with a DVM or have the tools like in the video.
You may have to rig up a DVM to put in the truck to monitor the solenoid when the SES light comes on.
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