ECM installation

[nates94xj]

I bought a spare ECM, or ECU, to take out in the boonies with me. Anything I should know before installing it to test it besides disconnecting the battery? Will it run poorly for a bit while the computer "learns" the new car? Thanks

 

[Durango-Bob]

The ECU is different depending on if the Jeep has an automatic or a stick. If yours came from the same equiped doner, it will be fine. It will probably do the learning thing, too. And don't be shocked if it throws a code.

 

[nates94xj]

Thanks Bob! The code will go away after 50 starts or something like that, right?

 

[Matthew Currie]

I think it's 40 starts. I've never had problems with "learning," and I have yet to see any documentation that either the Renix or Chrysler ECU has any learning function, other than pehraps canceling running codes and whatever limp-home modes it initiates when things go wrong, which may take a few starts. I noticed that my 95 ran strangely for a few miles after I had to replace the cam sensor, but the period was very brief, and on others I've never noticed a difference after replacing either sensors or the ECU itself.

 

[Ecomike]

I think it's 40 starts. I've never had problems with "learning," and I have yet to see any documentation that either the Renix or Chrysler ECU has any learning function, other than pehraps canceling running codes and whatever limp-home modes it initiates when things go wrong, which may take a few starts. I noticed that my 95 ran strangely for a few miles after I had to replace the cam sensor, but the period was very brief, and on others I've never noticed a difference after replacing either sensors or the ECU itself.

Based on FSMs I have read, and personal experience, They do have a learning memory map that they build up of min and max sensor value data, some of which can do odd things if it stores bad values, or if the jeep is not driven right away.