The Plight of the lean codes
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Mudding
Joined: Sep 2010
Posts: 230
Likes: 9
From: Hudson Valley, New York
Do you have lean codes for both banks or just one bank? An exhaust leak on one bank, will not effect the fuel trims on the other bank. So if both banks are lean, then you either have exhaust leaks on both sides, or you have a global issue (effects both banks, i.e. MAF sensor, intake leak, low fuel pressure, etc...).
Both banks are lean. Based on the images I posted - do my fuel trims look abnormal ?
I like your comments. It at least centers me. It doesn’t seem plausible that I have leaks on both sides (unless it’s exhaust manifold ?)
Three Wheeling
Joined: Mar 2015
Posts: 92
Likes: 17
When I bumped into the lean code issue, while it was only one bank, i went ahead and checked exhaust manifold bolts on both side and they were both on the loose side - so don't necessarily dismiss them. I doubt it's your issue but it worth a check. Also, I didn't see where you posted the actual lean codes, are they pre or post cat?
Rock Crawling
Joined: Jul 2019
Posts: 314
Likes: 26
From: Londonderry NSW AU
Some temporary fix that clamp is. The o2 sensors tell the ecu when to lean the fuel, so as you have 'lean' codes I would not think it is an exhaust or o2 problem but more an air input or lack of it, problem. You have checked the air filter and throttle body??
Exhaust leaks will certainly cause a lean code. Its called an Oxygen Sensor because it detects Oxygen. Exhaust goes through the manifold in "pulses", which is why exhaust leaks make a "puff puff" sound. When its not expelling exhaust, its drawing outside air in. This air drawn in, contains 21% Oxygen and the sensor doesn't know there is a leak, it just assumes its from the engine and tells the ECU that the fuel mixture is too lean.
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