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The engine control module (ECM) controls a Closed Loop air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. The ECM monitors the heated oxygen sensor (HO2S) signal voltage, and adjusts the fuel delivery based on the signal voltage while in Closed Loop. A change made to the fuel delivery changes the long and short term fuel trim values. The short term fuel trim values change rapidly in response to the HO2S signal voltages. These changes fine tune the engine fueling. The long term fueltrim values change in response to trends in the short term fuel trim The long term fuel trim makes coarse adjustments to fuel ingin order to re-center and restore control to short term fuel trim. The ideal fuel trim values are around 0 %. A positive fueltrim value indicates that the ECM is adding fuel in order to compensate for a lean condition. A negative fuel trim value indicates that the ECM is reducing the amount of fuel in order to compensate for a rich condition.
 

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Bigb - how do you know so much about these vehicles? Are you a tech ? What is your background ? Thx
 

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Bigb - how do you know so much about these vehicles? Are you a tech ? What is your background ? Thx

Big B is a superb and knowledgeable tech for sure . . :notworthy::notworthy::notworthy:
 
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Discussion Starter #25
Have put around 1,000 miles on it since I did the misc things like 02 sensor, cleaning tb, vvt sensors etc and zero check engine light. So that's fixed. Today drained the transmission and decided if it is black and burned smelling will get a service at a shop. So drained it and was not bad, still smelled fine(the Terrain has 54,xxx miles, fluid was darker but not what I expected it to be, was much better. So I filled with fresh valvoline synthetic fluid and will drain again around every 10k.since I have a case of havoline synthetic, after a couple changes should be good. Magnet on drain had zero metal, I couldn't see anything, actually was Shiney like stainless steel, I expected to see something on it. All that's left now is the differentials and I have mobile 1 75w90. Oil was at 50% life when I bought the Terrain, is down now to around 20%, zero oil use and is still clear and smells like fresh oil. So happy with everything do far.
 

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Discussion Starter #26
Have put around 1,000 miles on it since I did the misc things like 02 sensor, cleaning tb, vvt sensors etc and zero check engine light. So that's fixed. Today drained the transmission and decided if it is black and burned smelling will get a service at a shop. So drained it and was not bad, still smelled fine(the Terrain has 54,xxx miles, fluid was darker but not what I expected it to be, was much better. So I filled with fresh valvoline synthetic fluid and will drain again around every 10k.since I have a case of havoline synthetic, after a couple changes should be good. Magnet on drain had zero metal, I couldn't see anything, actually was Shiney like stainless steel, I expected to see something on it. All that's left now is the differentials and I have mobile 1 75w90. Oil was at 50% life when I bought the Terrain, is down now to around 20%, zero oil use and is still clear and smells like fresh oil. So happy with everything so far.
 

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Discussion Starter #27
Odd, I have a lot of issues using this forum on my phone. Tried mobile view, non mobile, desktop etc, right now I can't find the edit to remove the double post but everything else is there. Bonus on the Terrain I found out it has a active xm account, will see I guess how long that lasts. ( Once I posted this, Edit returned, but I can only edit this actual post, not previous ones since no edit is available.
 

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Odd, I have a lot of issues using this forum on my phone. Tried mobile view, non mobile, desktop etc, right now I can't find the edit to remove the double post but everything else is there. Once I posted this, Edit returned, but I can only edit this actual post, not previous ones since no edit is available.
They give you something like 24 hours to edit a post, then it’s locked and you have to ask an “admin” for help. Send a Private Message (PM) to “admin” AND “admin2” to get the duplicate removed.

Also - I used the “Mobile Enhanced” version on my iPhone (because it’s a little faster and easier to read), but you can’t “Like” posts. Have to switch to the “Full” version to do that.
 
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