Uploaded September 2016 | Updated September 2026, 2 weeks ago
Understanding these short and long term fuel trims are the basis of many repairs on modern vehicles. These fuel trims are basically corrections by the oxygen sensors (often called O2) sensors from miscalculation from sensors prior to the combustion of air and fuel. Or those sensors calculated correctly but there are issues with performance of any number of parts...including the oxygen sensors themselves.
I created this video in response to how fuel trims behaved when my fuel pump was acting up.
So what do you do when you fuel pump gets weak on you on traffic? Most people push on the gas pedal more. I'll explain why this doesn't work and I'll also add this to my engine and component diagnostic series.
I'll answer the questions, " How does that feel? How's it look on sensors?"
If your O2 sensors go flat lean, it could be because you're not getting enough fuel. Fuel trims correct for lean by trying to add a lot more fuel. Then long term fuel trims (LTFT) remember what it took to get enough, if it even can and short term fuel trims (STFT) go back to hovering around zero.
Quiz:
Does pushing on the gas pedal when your short on fuel help?
No it doesn't. If you can't keep up with the fuel flow, then you'll just make the engine go even leaner, and even eat itself, let alone die. Yes, that's right, all the aluminum in your engine becomes fuel if your engine is ran too lean.
What's the cause of fuel trims? O2 sensors catching anything that went into combustion was off and needed correction. It could be a MAF that shows different air flow than reality, it could be a fuel pump under producing like it was in this video, it could even be the O2 sensors lying.
I think hypermilers don't get that when they mod their cars to run too lean all the time!
Do you want your engine to run on gasoline or on engine?
HO2S is how the oxygen sensor data will often show up abbreviated on your scan tool's diagnostic live data.
Due to factors beyond the control of DE Nichols/AutoBravado it cannot guarantee against unauthorized modifications of this information, or improper use of this information. DE Nichols/AutoBravado assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. DE Nichols/AutoBravado recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of DE Nichols/AutoBravado, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not DE Nichols/AutoBravado.
#ShortTermFuelTrim #LongTermFuelTrim #FuelTrims
Understanding these short and long term fuel trims are the basis of many repairs on modern vehicles. These fuel trims are basically corrections by the oxygen sensors (often called O2) sensors from miscalculation from sensors prior to the combustion of air and fuel. Or those sensors calculated correctly but there are issues with performance of any number of parts...including the oxygen sensors themselves.
I created this video in response to how fuel trims behaved when my fuel pump was acting up.
So what do you do when you fuel pump gets weak on you on traffic? Most people push on the gas pedal more. I'll explain why this doesn't work and I'll also add this to my engine and component diagnostic series.
I'll answer the questions, " How does that feel? How's it look on sensors?"
If your O2 sensors go flat lean, it could be because you're not getting enough fuel. Fuel trims correct for lean by trying to add a lot more fuel. Then long term fuel trims (LTFT) remember what it took to get enough, if it even can and short term fuel trims (STFT) go back to hovering around zero.
Quiz:
Does pushing on the gas pedal when your short on fuel help?
No it doesn't. If you can't keep up with the fuel flow, then you'll just make the engine go even leaner, and even eat itself, let alone die. Yes, that's right, all the aluminum in your engine becomes fuel if your engine is ran too lean.
What's the cause of fuel trims? O2 sensors catching anything that went into combustion was off and needed correction. It could be a MAF that shows different air flow than reality, it could be a fuel pump under producing like it was in this video, it could even be the O2 sensors lying.
I think hypermilers don't get that when they mod their cars to run too lean all the time!
Do you want your engine to run on gasoline or on engine?
HO2S is how the oxygen sensor data will often show up abbreviated on your scan tool's diagnostic live data.
Due to factors beyond the control of DE Nichols/AutoBravado it cannot guarantee against unauthorized modifications of this information, or improper use of this information. DE Nichols/AutoBravado assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. DE Nichols/AutoBravado recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of DE Nichols/AutoBravado, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not DE Nichols/AutoBravado.
#ShortTermFuelTrim #LongTermFuelTrim #FuelTrims
