P0171 code(check engine)
Thread Starter
Intermediate
Joined: Aug 2020
Posts: 37
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From: denver
P0171 code(check engine)
I have 03 c5z and the check engine light came on, when I scanned the car it showed P0171 code what is the possible issue and is it to bad? And how can i fix it?
Instructor
Joined: Jan 2019
Posts: 215
Likes: 223
From: Atlanta, GA
P0171 is a lean condition in bank 1. Check for vacuum leaks, exhaust leaks (pre cat), or loose intake bolts. I had P0171 and 174 (both banks lean), it ended up being a loose intake. Intake bolts are supposed to be torqued to 89 inch pounds
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,613
Likes: 4,061
From: Cape Coral, Florida
Have you had any of the intake components off recently ??…I’d look anywhere between the MAF sensor and throttle body for an intake bellows leak…a 0171 is bank 1 but your bank 2 fuel trims (LTFT’s which set the code) may be close to the percentage that illuminate the MIL…if just a 0171 we turn right…if both LTFT are elevated we turn left…do you have a scan tool or did you use the cars built in code reader ??….now this can be a few other things so we can start there…if you have a scan tool I can show you how to quickly diagnose a vacuum leak !!…I will move this thread to Tech !!
Last edited by C5 Diag; Sep 2, 2021 at 08:07 PM.
Advanced
Joined: Sep 2020
Posts: 62
Likes: 31
From: Florida
This is a normal code if you have installed any aftermarket intake as well. Even just a k@n drop in filter will cause this code. The ECU is very sensitive to any changes. It might be OK with just a filter. I installed a filter that the previous owner never got around to doing and I got the code a couple of times going WOT the first 100 miles or so. But now I dont seem to get it anymore. I'm just waiting to buy headers and a full intake. That of course requires a proper tune and that would fix any lean issues. If you dont plane on getting a full tune you can send your ECU to a company like ECS and they can flash it for just 150 bucks.
