LEAN CODE ONE BANK ONLY:
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LEAN CODE ONE BANK ONLY:
Sometimes a lean code will set for only one bank.
Often it is accompanied by a miss fire code or by no other code.
How is it possible for only one bank to run Lean if the motor runs perfect but a bit of a hog on gas mileage? A hint!
The lean condition is detected by the Oxygen sensor so it is indeed there somewhere if the sensor switches normally per Scanner check. Believe it.
Since the sensor is located a few inched below the exhaust manifold outlet at the ball and flange seal, that area is the only place a leak can be detected for this problem.
.
How to find the leak; Use a mechanics stethoscope with the tip removed back to the holder so you can hear the sound of the leak with the motor running as picked up by the holder.
.
Back ground; Sometimes if the Long Term Fuel Trims are checked with a Scanner, you might see one bank greatly different than the other that matches the code set.
It is possible for the bank with the code set....NOT...... to be shifted to the normal 25% that normally is required to set the code.
How come? It appears the PCM program has the built in ability to track a large difference between the two LTFT percentage values as an abnormal condition which can set the code and CEL dash light.
.
Back to the exhaust leak; since the leak is before the OX Sensor and after all the cylinder exhaust, the answer is outside air is being drawn into the exhaust such that the OX Sensor detects this and richens up that bank >falsely<.
This puts the difference between the LTFT tables too far apart even though one is not out to the limit that normally sets code..
.
How does air get drawn in instead of exhaust pressure out the leak?
There are two things that can happen.
1. Exhaust flowing by the leak can draw outside air into the mix.
2. Acoustic tuning in gas speeds can produce a momentary vacuum at the leak point such that outside air tries to fill the vacuum due to outside Barometric pressure.
This is also RPM and Temperature sensitive.
There are variations of this to the same end result.
.
The above is a testament to how good the computer control is for these engines.
The above is easy to find but a b*tch to fix sometimes.
Good luck.
Often it is accompanied by a miss fire code or by no other code.
How is it possible for only one bank to run Lean if the motor runs perfect but a bit of a hog on gas mileage? A hint!
The lean condition is detected by the Oxygen sensor so it is indeed there somewhere if the sensor switches normally per Scanner check. Believe it.
Since the sensor is located a few inched below the exhaust manifold outlet at the ball and flange seal, that area is the only place a leak can be detected for this problem.
.
How to find the leak; Use a mechanics stethoscope with the tip removed back to the holder so you can hear the sound of the leak with the motor running as picked up by the holder.
.
Back ground; Sometimes if the Long Term Fuel Trims are checked with a Scanner, you might see one bank greatly different than the other that matches the code set.
It is possible for the bank with the code set....NOT...... to be shifted to the normal 25% that normally is required to set the code.
How come? It appears the PCM program has the built in ability to track a large difference between the two LTFT percentage values as an abnormal condition which can set the code and CEL dash light.
.
Back to the exhaust leak; since the leak is before the OX Sensor and after all the cylinder exhaust, the answer is outside air is being drawn into the exhaust such that the OX Sensor detects this and richens up that bank >falsely<.
This puts the difference between the LTFT tables too far apart even though one is not out to the limit that normally sets code..
.
How does air get drawn in instead of exhaust pressure out the leak?
There are two things that can happen.
1. Exhaust flowing by the leak can draw outside air into the mix.
2. Acoustic tuning in gas speeds can produce a momentary vacuum at the leak point such that outside air tries to fill the vacuum due to outside Barometric pressure.
This is also RPM and Temperature sensitive.
There are variations of this to the same end result.
.
The above is a testament to how good the computer control is for these engines.
The above is easy to find but a b*tch to fix sometimes.
Good luck.
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