GaryG
10-15-2006, 07:01 AM
Resetting Keep Alive Memory (KAM)
It may be necessary to reset the KAM in the PCM to the default setting after a Diagnostic Trouble Code (DTC) causes a engine or vehicle warning light. Other conditions may not produce a warning light, such as ethanol and poor performance conditions related to fuel mixtures that may warrant a reset. KAM creates adaptive learning contents such as idle speed, refueling event, and fuel trim.
For instance, after refueling and driving a short distance, I noticed a big decrease in FE. This has occurred a few times and is from a gas mixture that used oxygenates (ethanol), sometimes referred to winter gas. I no longer fill up at Citgo stations as a result.
Due to the fact that % of alcohol or oxygenates are not as combustible as gasoline, the oxygen sensors send a message to the PCM that there is a lean fuel trim and it makes an adjustment for a richer air/fuel mixture. The PCM alters the air/fuel ratio maps at the different RPM’s and engine load points, and the KAM stores this data as the long term fuel trim. There is not much you can do at this point other than burn the entire tank of gas. Once you refill with straight gas, it may take a few tanks for the PCM to adjust all the long term fuel trim maps stored in the KAM for each RPM/Load point. This means you will be getting a richer air/fuel mix at closed loop modes and your MPG will be reduced accordingly. In the past, I didn’t understand why my FEH continued to get poor MPG after I replaced the fuel with straight gasoline. After refueling a few times, my MPG returned to normal because the PCM eventually readjusted the air/fuel mixtures at all RPM’s and engine load points in the KAM air/fuel maps.
Any time the FEH has had a condition that may have altered KAM, a reset to the default mode can be done by using one of two methods. Adaptive learning contents such as idle speed, refueling event, and fuel trim are included in the reset of KAM. To clear the continuous DTCs in the PCM and have it reset the emissions monitors information, is also part of a KAM reset. Both can be useful in post repair or a big change in driving conditions. KAM can be reset by a diagnostic tool or by disconnecting the 12V battery ground cable for a minimum of 5 minutes.
After the KAM has been reset, the vehicle may exhibit certain driveability concerns. It is necessary to drive the vehicle to allow the PCM to learn the values for optimum performance. My recommendation would be to reset the KAM after the vehicle is warm and drive the most fuel efficient way possible afterwards. Always remember that KAM is reset when the battery is disconnected for more than 5 minutes.
GaryG
It may be necessary to reset the KAM in the PCM to the default setting after a Diagnostic Trouble Code (DTC) causes a engine or vehicle warning light. Other conditions may not produce a warning light, such as ethanol and poor performance conditions related to fuel mixtures that may warrant a reset. KAM creates adaptive learning contents such as idle speed, refueling event, and fuel trim.
For instance, after refueling and driving a short distance, I noticed a big decrease in FE. This has occurred a few times and is from a gas mixture that used oxygenates (ethanol), sometimes referred to winter gas. I no longer fill up at Citgo stations as a result.
Due to the fact that % of alcohol or oxygenates are not as combustible as gasoline, the oxygen sensors send a message to the PCM that there is a lean fuel trim and it makes an adjustment for a richer air/fuel mixture. The PCM alters the air/fuel ratio maps at the different RPM’s and engine load points, and the KAM stores this data as the long term fuel trim. There is not much you can do at this point other than burn the entire tank of gas. Once you refill with straight gas, it may take a few tanks for the PCM to adjust all the long term fuel trim maps stored in the KAM for each RPM/Load point. This means you will be getting a richer air/fuel mix at closed loop modes and your MPG will be reduced accordingly. In the past, I didn’t understand why my FEH continued to get poor MPG after I replaced the fuel with straight gasoline. After refueling a few times, my MPG returned to normal because the PCM eventually readjusted the air/fuel mixtures at all RPM’s and engine load points in the KAM air/fuel maps.
Any time the FEH has had a condition that may have altered KAM, a reset to the default mode can be done by using one of two methods. Adaptive learning contents such as idle speed, refueling event, and fuel trim are included in the reset of KAM. To clear the continuous DTCs in the PCM and have it reset the emissions monitors information, is also part of a KAM reset. Both can be useful in post repair or a big change in driving conditions. KAM can be reset by a diagnostic tool or by disconnecting the 12V battery ground cable for a minimum of 5 minutes.
After the KAM has been reset, the vehicle may exhibit certain driveability concerns. It is necessary to drive the vehicle to allow the PCM to learn the values for optimum performance. My recommendation would be to reset the KAM after the vehicle is warm and drive the most fuel efficient way possible afterwards. Always remember that KAM is reset when the battery is disconnected for more than 5 minutes.
GaryG