How do I reset my Toyota fuel trims?
To perform a PCM reset…
- Bring car up to normal operating temp.
- Turn ignition off.
- Remove ECM main fuse.
- Turn ignition to “on”, do not start.
- Wait for system check to complete, numerous errors will be detected.
- Turn ignition off.
- Replace fuse.
- Turn ignition to “on” and wait for system check.
What should STFT be while driving?
When everything is stable and working correctly, fuel trim numbers should be no greater than 10%, and total fuel trim should be no more than 10% when the numbers are added together. For example, if LTFT is 4% and STFT is 4%, the total is 8%: that’s acceptable.
What is STFT and Ltft?
The short term and long term fuel trims are used to regulate fuel delivery for optimal combustion. There are two types of fuel trim – short term (STFT) and long term (LTFT). STFT is used for immediate adjustments based on the parameters, whereas the LTFT is a slower adjustment.
Will disconnecting battery reset fuel trims?
This is done by disconnecting the battery, waiting for 10 minutes or so, and/or turning the ignition key to the starter position to discharge the system. Note, the code “Erase” button on scanners does not reset the LTFT, at least not on my S70.
What causes positive fuel trims?
Positive fuel trim is caused by ‘leaner’ combustion than the the ECM or PCM predicted. Clogged or unresponsive fuel injectors. Ignition misfires caused by fouled spark plug, weak ignition coil or bad spark plug wires. Damaged exhaust valve that allows unburned oxygen into exhaust.
What does STFT and LTFT mean on a laptop?
The scan tool will show STFT readings that are in the positive double digits, indicating that the computer has been adding too much fuel for normal operation. After a while the LTFT will also reflect this relative addition in fuel.
What’s the difference between STFT and LTFT fuel trims?
It’s similar with short and long-term fuel trims. STFT are immediate ups and downs in fuel, while LTFT are what is occurring over a longer period. A normal STFT reading will generally fluctuate between negative and positive single digits 2-3 times per second.
What does STFT mean when fuel is added too much?
The computer will maintain this heightened addition of fuel until the leak is corrected. The scan tool will show STFT readings that are in the positive double digits, indicating that the computer has been adding too much fuel for normal operation. After a while the LTFT will also reflect this relative addition in fuel.
How often does a STFT reading go up or down?
A normal STFT reading will generally fluctuate between negative and positive single digits 2-3 times per second. Usually they’ll stay around positive or negative 5%, but they may occasionally go up towards 8 or 9% depending on the efficiency of the engine, age of the components, and other factors.