ECM Re-learn
Advanced
Joined: Jul 2006
Posts: 57
Likes: 0
From: University of Alabama at Birmingham School of Dentistry
I know at least with the L98 cars, when the battery is disconnected from the ECM for any length of time, the ECM loses certain information that isnt permanently stored in memory that relates to your specific driving habits. When you reconnect the battery, it must re-learn this info, which it does automatically.
Safety Car
Joined: Sep 2003
Posts: 3,599
Likes: 24
From: Orange County NY
St. Jude Donor '10-'11-'12-'13
In open loop, the ECM uses sensor data to determine proper fuel delivery. However, without feedback from the O2 sensor, it really has no idea if the amount of fuel being delivered is too much (rich) or too little (lean). Once in closed loop with feedback from the O2 sensor (at idle and part throttle cruise), the ECM will constantly adjust the amount of fuel being delivered to achieve a 14.7:1 air/fuel ratio. Over time, the ECM may need to make minor corrections to the amounts of fuel delivered at certain times, based on changes in air flow. The ECM stores these changes in memory so that it can refer back to them, even in open loop.
If you disconnect the battery, this memory will be erased. When you reconnect the battery, the ECM will go back to using the "unadjusted" fuel delivery numbers in open loop. The ECM needs to go into closed loop and the car needs to be driven around for a bit in order for the ECM to "re-learn" any corrections it had been making.
Not the best explanation (there are full chapters of books devoted to this subject), but hopefully you get the idea.
If you disconnect the battery, this memory will be erased. When you reconnect the battery, the ECM will go back to using the "unadjusted" fuel delivery numbers in open loop. The ECM needs to go into closed loop and the car needs to be driven around for a bit in order for the ECM to "re-learn" any corrections it had been making.
Not the best explanation (there are full chapters of books devoted to this subject), but hopefully you get the idea.
Racer
Joined: Sep 2005
Posts: 271
Likes: 0
From: New Freedom PA
In open loop, the ECM uses sensor data to determine proper fuel delivery. However, without feedback from the O2 sensor, it really has no idea if the amount of fuel being delivered is too much (rich) or too little (lean). Once in closed loop with feedback from the O2 sensor (at idle and part throttle cruise), the ECM will constantly adjust the amount of fuel being delivered to achieve a 14.7:1 air/fuel ratio. Over time, the ECM may need to make minor corrections to the amounts of fuel delivered at certain times, based on changes in air flow. The ECM stores these changes in memory so that it can refer back to them, even in open loop.
If you disconnect the battery, this memory will be erased. When you reconnect the battery, the ECM will go back to using the "unadjusted" fuel delivery numbers in open loop. The ECM needs to go into closed loop and the car needs to be driven around for a bit in order for the ECM to "re-learn" any corrections it had been making.
Not the best explanation (there are full chapters of books devoted to this subject), but hopefully you get the idea.
If you disconnect the battery, this memory will be erased. When you reconnect the battery, the ECM will go back to using the "unadjusted" fuel delivery numbers in open loop. The ECM needs to go into closed loop and the car needs to be driven around for a bit in order for the ECM to "re-learn" any corrections it had been making.
Not the best explanation (there are full chapters of books devoted to this subject), but hopefully you get the idea.
