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Discussion Starter · #1 ·
Thought i had a vacuum leak, but sprayed a crap load of ether under the hood and found nothing. The problem is that the cruise control will not engage unless u got ur foot on the gas and the engine is in the boost and out of the vacuum. It kicks in, but as soon as u get out of the boost and back in the vacuum it shuts off, and after messing with is it throws a check engine light on with an error code of leane on one of the banks, but not both. I know the system is not leane because i monitor it with a wide band AFR gage. Any ideas?

thanks Vlad.
 

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and after messing with is it throws a check engine light on with an error code of leane on one of the banks, but not both. I know the system is not leane because i monitor it with a wide band AFR gage. Any ideas?

thanks Vlad.
Let's separate the two issues.

A lean bank code can easily be caused by an exhaust leak.

While in closed loop (idle and part throttle), the PCM monitors the O2 sensors, and adjusts the fuel to keep it running very close to stoich (14.64). If the PCM detects too much oxygen, it adds fuel to try to get it back to stoich. It keeps track of how much fuel it is adding (or subtracting) in the short term fuel trims. After a while, the short term fuel trims are transferred to the long term trims and the two are added together. When the PCM reaches a pre-programmed limit for the fuel trims (I think stock is 25% as I recall), it sets the lean bank code (or rich if the PCM is pulling fuel.)

So you are going to see pretty darned close to stoich on your wideband because the PCM is doing its best to keep it there. You really need to log your fuel trims to see the real problem.

With your exhaust leak, oxygen molecules are getting in via the leak and are confusing the PCM. It thinks the oxygen is coming through the combustion chamber unburned.

Now that you have fixed your exhaust leak (unless broken motor mounts cause it to leak right away again) you should clear the code. Then you can either drive it for a while to let the fuel trims fall back to normal, or you can unhook the battery, press on the brake pedal a few times to drain the capacitors that power the KAM. I am pretty sure the KAM holds the LTFTs so you will be starting over at that point. If the exhaust leak was the culprit, the lean bank code should not come back.

I think the cruise control issue is a different issue. I have no idea about that.
 

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Discussion Starter · #3 ·
Let's separate the two issues.

A lean bank code can easily be caused by an exhaust leak.

While in closed loop (idle and part throttle), the PCM monitors the O2 sensors, and adjusts the fuel to keep it running very close to stoich (14.64). If the PCM detects too much oxygen, it adds fuel to try to get it back to stoich. It keeps track of how much fuel it is adding (or subtracting) in the short term fuel trims. After a while, the short term fuel trims are transferred to the long term trims and the two are added together. When the PCM reaches a pre-programmed limit for the fuel trims (I think stock is 25% as I recall), it sets the lean bank code (or rich if the PCM is pulling fuel.)

So you are going to see pretty darned close to stoich on your wideband because the PCM is doing its best to keep it there. You really need to log your fuel trims to see the real problem.

With your exhaust leak, oxygen molecules are getting in via the leak and are confusing the PCM. It thinks the oxygen is coming through the combustion chamber unburned.

Now that you have fixed your exhaust leak (unless broken motor mounts cause it to leak right away again) you should clear the code. Then you can either drive it for a while to let the fuel trims fall back to normal, or you can unhook the battery, press on the brake pedal a few times to drain the capacitors that power the KAM. I am pretty sure the KAM holds the LTFTs so you will be starting over at that point. If the exhaust leak was the culprit, the lean bank code should not come back.

I think the cruise control issue is a different issue. I have no idea about that.
I have cleared the code multiple times with the X-cal. The thing is, even with the exhaust leak the check engine light will not come on unless u try to mess with the cruise control. And i am talking about no matter what kind of driving u do, as long as you dont touch the CC, the check angine light stays on. The second u touch the buttons for CC though it tryes to engage and dosent, and the check engine light comes on.
 
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