Code U0109
Thread Starter
Teching In
Joined: Nov 2018
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Code U0109 I built a gen 4 6.0 LS and my wiring harness is pinned for a ls3 maf. The ecm is e38 with a stock 2008 Chevy truck tune. The problem is when I start the engine it runs rich and will sometime die and throws code U0109. If I unplug the maf it corrects itself and runs great. So I got a new ls3 maf sensor and no change, it runs rich and will die. What am I missing???? The maf sensor is near the filter and I have it on a 4 inch tube. Could the air be disturbed too much in a 4 inch tube? Or something similar causing the issue?
TECH Fanatic
Joined: Oct 2014
Posts: 1,220
Likes: 179
From: Virginia
That code "Lost communication with fuel pump module" which could explain your problem. Might check the wiring, would be something to at least look into. Also, MAF sensors are pretty inaccurate at idle, and depending on your cam and how much overlap you might have, can make things worse with a "false lean" condition in the exhaust at idle. This will make the PCM think it's lean and dump fuel to try and correct it. It doesn't know that the air is coming from overlap, similar to a big exhaust leak. As RPM goes up this problem goes away but STFT's at idle can cause some real issues if your cam has overlap.
Thread Starter
Teching In
Joined: Nov 2018
Posts: 2
Likes: 0
It’s just a standard ls6 cam nothing crazy. I spoke to my harness guy, because I thought maybe wiring issue but he swears it’s not. Like you stayed it does smooth out if I rev it like around 2k rpm. Maybe the maf data in the pcm is way off since it’s a stock 2008 Chevy Silverado ecm, but you would think it would run better than it does.
