Where should fuel trim be?
Ideally, long-term fuel trims should be at, or close to 0% when the engine is running at a steady speed. However, while changes to the engine speed will (and must) produce changes in the long-term fuel trim value, this value should return to a point close to 0% when the engine speed steadies.
Where is fuel trim bank1?
For a technical understanding of fuel trim, you can read our in-depth explanation here. Bank 1 is either the only bank (as in with an in-line 4 cylinder) or the bank where #1 cylinder is located on a 6 cylinder or a V8. The ECM/PCM and the O2 sensor are all about keeping things balanced in the combustion chamber.
What is fuel bank trim?
Fuel Trim is the adjustment the engine computer (PCM) makes to the fuel mixture to maintain a balanced air/fuel ratio. Fuel trim is usually displayed as a PERCENTAGE reading on a scan tool. A rich fuel mixture can produce more power (up to a point) but it also increases fuel consumption and emissions.
What should the bank rich be on fuel trim?
The fuel trim values would be on the negative side and we would likely have a P0172/P0175 (Bank 1 and 2 Rich). Clogged or contaminated injectors should be checked, but only after diagnosing the components listed in the previous paragraph.
When to use fuel trim to identify a problem?
Fuel trim can also be used to identify which bank of cylinders is causing a problem. If the LTFT for bank 1 is 20% and the LTFT for bank 2 is 3%, the source of the problem is associated with bank 1 cylinders only.
Where is the fuel trim data stored on a GMH?
Remember, Fuel Trim data contained in either scanner Freeze Frame mode, or, that contained in Enhanced Data mode is of vital importance, so always check both scanner modes during diagnostics. Fuel Trim Data Storage
Why is my fuel trim on the negative side?
Leaking or contaminated fuel injectors were listed as possible causes for these fault codes, but leaking fuel injectors would create a richer-than-normal air/fuel mixture. The fuel trim values would be on the negative side and we would likely have a P0172/P0175 (Bank 1 and 2 Rich).
What should bank 1 fuel trim be at idle?
If long-term fuel trim (LTFT) for bank 1 is 25% at idle, but corrects to 4% at 1,500 and 2,500 rpm, focus on factors that cause a lean condition at idle, such as a vacuum leak.
Fuel trim can also be used to identify which bank of cylinders is causing a problem. If the LTFT for bank 1 is 20% and the LTFT for bank 2 is 3%, the source of the problem is associated with bank 1 cylinders only.
What does fuel trim mean on an ECM?
Fuel trim is what the ECM implements to adjust the air-fuel ratio of the engine according to changing driver conditions. The air-fuel ratio should stay at, or very near to 14.7:1.
When to turn off long term fuel trims?
However, when long-term fuel trims exceed about 10% or so to either side of 0%, there is a problem that needs to be investigated, but note that codes indicating rich or lean running conditions will generally only be set when the deviation reaches about 25% or so.