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Extreme Fuel Trim Numbers on Launch X431 V+

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5 years 2 months ago - 5 years 2 months ago #26230 by Kenyamyhome
I don't seem to understand the levels of Fuel Trim as attached below. 100% for both Short & Long Term trims. Anybody with an idea on it and i will be appreciative. Thanks
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Last edit: 5 years 2 months ago by Kenyamyhome.

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5 years 2 months ago #26231 by cj1
what vehicle are you using it on?
Suppose that 100% is normal and above adds fuel below subtracts.

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5 years 2 months ago #26234 by Tyler
cj1 is right. You're looking at a Nissan (or Infiniti), which uses Alphas as it's fuel trim designation. 100% represents 0% correction, OR an open loop condition. Less than 100% is a negative correction, more is positive. For example, 115% on your scan data is +15% to everyone else.

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5 years 2 months ago #26242 by Kenyamyhome
Thanks buddy, its a Nissan Sylphy, 2006.

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5 years 2 months ago #26243 by Kenyamyhome
Hey Tyler, its true its a Nissan Sylphy, 2006. So am happy and at the same time surprised that the 100% trim figure means zero correction. Actually i do have a " P0868 fluid pressure low" that gets the vehicle struggling on slopes. If i drive for a few minutes, say 10 minutes, and i happen to stop on a slope for a minute, i wont be able to snap throttle or get the vehicle to move as it will stall for a few moments before it moves. That's even with pedal to the metal. As that happens, (pedal to the metal) speedometer stays still, engine stays quite until few moments later when it finally moves. I still don't know where to start from.

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5 years 2 months ago - 5 years 2 months ago #26250 by Andy.MacFadyen
Coolant temperature -- 114f --- only 46c it is likely still open loop how lomg had the engine been running ?

" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)



Last edit: 5 years 2 months ago by Andy.MacFadyen.
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5 years 2 months ago #26265 by Paul6004

Kenyamyhome wrote: Hey Tyler, its true its a Nissan Sylphy, 2006. So am happy and at the same time surprised that the 100% trim figure means zero correction. Actually i do have a " P0868 fluid pressure low" that gets the vehicle struggling on slopes. If i drive for a few minutes, say 10 minutes, and i happen to stop on a slope for a minute, i wont be able to snap throttle or get the vehicle to move as it will stall for a few moments before it moves. That's even with pedal to the metal. As that happens, (pedal to the metal) speedometer stays still, engine stays quite until few moments later when it finally moves. I still don't know where to start from.

We had a Nissan Cube doing that a while ago - turned out to be a sticking oxygen sensor.
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5 years 2 months ago - 5 years 2 months ago #26268 by Kenyamyhome
Thanks Paul6004. Excuse my lack of understanding. What did you mean when you said a sticking O2 sensor? ...So how did you go about sorting it. I will highly appreciate your response on this.
Just for clarification, i do have a P0141 HO2S2 HTR(B1) on my scanner.
Last edit: 5 years 2 months ago by Kenyamyhome.

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5 years 2 months ago - 5 years 2 months ago #26269 by Kenyamyhome
I believe it had not run much, but i was looking at a freeze frame. So, going by your judgement, it could be true that it might have been in open loop. What's the standard coolant temperature that triggers the closed loop?
Last edit: 5 years 2 months ago by Kenyamyhome. Reason: Gramatical

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5 years 2 months ago #26270 by Andy.MacFadyen
There are a few different conditions required for the engine to run closed loop mainly the coolant temperature and the O2 sensor becoming active. If engine computer dosen't see the expected activity from the upstream O2 sensors it will revert to a fall open loop fueling map.

" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)



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5 years 2 months ago #26343 by Paul6004

Kenyamyhome wrote: Thanks Paul6004. Excuse my lack of understanding. What did you mean when you said a sticking O2 sensor? ...So how did you go about sorting it. I will highly appreciate your response on this.
Just for clarification, i do have a P0141 HO2S2 HTR(B1) on my scanner.

An oxygen sensor can get covered in dirt and give the wrong reading for a while, or fail electrically and stop switching lean-rich-lean-rich
and just stay on one of them making the ECU think there is an issue with fuel mixture.

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5 years 2 months ago - 5 years 2 months ago #26367 by Andy.MacFadyen
O2 sensors need to be up to temperature to start responding, they also take longer to warm up and are slower to respond as they get older. Much the same applies to catalytic convertors.
On engines built since the mid-1990s when OBD2 was introduced there are heaters on the O2 sensor to speed the warming up process.
A P0141 code on a Nissan points to failure of the heater circuit on the rear oxygen sensor heater --- this can be either a failed O2 sensor or a short or open wiring to the sensor heater.

" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)



Last edit: 5 years 2 months ago by Andy.MacFadyen.

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