![]() Accordingly, the difference between the basic and theoretical mixture ratios is monitored in this system. Both manufacturing differences (i.e., mass air flow sensor hot wire) and characteristic changes during operation (i.e., fuel injector clogging) directly affect mixture ratio. However, the basic mixture ratio is not necessarily controlled as originally designed. The ECM controls the basic mixture ratio as close to the theoretical mixture ratio as possible. This feedback signal is then sent to the ECM. The mixture ratio feedback control system monitors the mixture ratio signal transmitted from air fuel ratio (A/F) sensor 1. If you don't have one, you can perform the "HOW TO ERASE EMISSION-RELATED DIAGNOSTIC INFORMATION" procedure manually, or you can just disconnect the battery and wait. Note that steps 6 through 8 are easy if you have a ScanGuage. Here's how to reset the "air fuel ratio self-learning control value" (discussed along with "ECU relearning" as "reset the ECU" or "ECU reset" in other threads) without disconnecting the battery, waiting for some unknown number of minutes or hours, and losing other settings like the radio station presets in the process. Run the engine for at least 10 minutes at idle speed. Refer to EC-61, "HOW TO ERASE EMISSION-RELATED DIAGNOSTIC INFORMATION".ĩ. Stop the engine and reconnect the mass air flow sensor harness connector.ħ. Restart the engine and let it idle for at least 5 seconds.ĥ. Disconnect the mass air flow sensor harness connector.Ĥ. Start the engine and warm it up to normal operating temperature.ģ. When clearing the coefficient of the self-learning control value THE COEFFICIENT OF SELF-LEARNING CONTROL MIXTURE RATIO RETURNS TO THE ORIGINAL COEFFICIENT. ![]() Such deviation will occur due to individual engine differences, wear over time, and changes in the usage environment. “Long-term fuel trim” is overall fuel compensation carried out long-term to compensate for continual deviation of the short-term fuel trim from the central value. The signal then triggers a reduction in fuel volume if the mixture ratio is rich, and an increase in fuel volume if it is lean. The signal from air-fuel ratio (A/F) sensor 1 indicates whether the mixture ratio is RICH or LEAN compared to the theoretical value. “Short-term fuel trim” is the short-term fuel compensation used to maintain the mixture ratio at its theoretical value. Fuel trim includes short-term fuel trim and long-term fuel trim. “Fuel trim” refers to the feedback compensation value compared to the basic injection duration. This is then computed in terms of “injection pulse duration” to automatically compensate for the difference between the two ratios. Both manufacturing differences (i.e., mass air flow sensor hot wire) and characteristic changes during operation (i.e., fuel injector clogging) directly affect the mixture ratio. The mixture ratio feedback control system monitors the mixture ratio signal transmitted from air-fuel ratio (A/F) sensor 1. If you don't have one, you can perform the "HOW TO ERASE EMISSION-RELATED DIAGNOSTIC INFORMATION" procedure manually, or you can just disconnect the battery and wait.Įxtracts from the Engine Control (EC) section of the 2006 Xterra service manual Note that steps 6 through 8 are easy if you have a language. I haven't checked the manuals for other years yet, but I would ASSUME (as in maybe YOU shouldn't) that the procedure is the same. Here are the relevant excerpts from the 2006 service manual. I would appreciate a second opinion from somebody, please, in case I'm sadly mistaken! It takes a bit longer than that, but the basic trick is to disconnect the MAF for at least 5 seconds. Here's how to reset the "air-fuel ratio self-learning control value" (discussed along with "ECU relearning" as "reset the ECU" or "ECU reset" in other threads) without disconnecting the battery, waiting for some unknown number of minutes or hours, and losing other settings as the radio station presets in the process. I was looking in the service manual for information about the mass air flow sensor when I stumbled upon a handy procedure.
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