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I am wondering if someone can tell me, if the battery has been disconected, will it reset the ecu so when a new battery is installed, any old codes would be lost? I am trying to avoid any excess troubleshooting. Thanks

 
Rep Power: 518

Disconnecting the battery erases most codes.

HTH

 
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Do you know what needs to occur before the ecu starts to show error codes again?

 
Rep Power: 518

A fault needs to be detected.

It doesn't have ESP.

 
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Yes indeed, but I was not clear. If a problem exsists and the ecu has been reset will it read the old problem, if one exsisted before it was reset.

 
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If the fault that triggered the code prior to the reset has not been corrected, then it will detect that fault and activate the code again.

 
Rep Power: 518

If a problem exists and the ecu has been reset it will read the old problem.

 
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Thanks for that. I am still wondering will the ecu show codes as soon as the battery is reconnected or does something else need to happen, like the car has to be running, the key has to have been turned on 100 times, etc, before will show codes again. In case you could not tell, this is a learning experence for me.

 
Rep Power: 285

The ECU needs to detect the fault again for the code to be activated.

In order for the ECU to detect a fault, a fault must occur.

A fault is not predictable, it may occur the first time the engine reaches operating temperature post reset or after several hours of driving if not longer.

 
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Well the 90' civic si is Resurected! After sitting for 5+ years, I followed the steps outlined by ezone (months ago) and started troubleshooting the electrical. I resoldered the s**t out of the main relay, put some oil in the plug holes and started cranking. Took a little while, but she finally built up enough compression to catch. Sure did blow some smoke! but by the end of the drive (15mi or so) she was sounding real smooth. Got a Nasty high speed shimmy, tires are toast I am guessing. Still no ecu codes, guess I will wait and see about that. looking forward to driving this Fun and economical rig again!