I have a 1985 DeVille and a 1997 DeVille.

After viewing the trouble codes how do you reset them in both of these years.

I presume that resetting codes is necessary to see if an intermittent problem has been solved.

I have the original GM shop manuals for both cars but I can't find instructions to reset the codes. Section 6EE seems to be missing from the 1997 manual.

 

unhook the battery for a minute

 

Disconnecting the battery doesn't work in the 97. The original battery finally gave up the ghost and I changed it. Then I discovered misfire codes, changed the plug wires, and wanted to reset the codes to see if they would come back.

In the 85 disconnecting the battery clears some codes but sets a battery failure code.

I know there is a sequence of buttons to hit to step through all the tests and then you can clear the codes, but I don't know what it is.

 

I think the answer for the 97 is in the FAQ section of this site. On the 01 you press the INFO and UP button on the driver's info to get started. Then follow the instructions on the dash using the buttons for input.

 

I browsed through the FAQ section but couldn't find anything about resetting the codes. On both the 85 and 97 you press OFF and WARMER to start diagnostics, it then displays the error codes and then ends with something cryptic like "ECM ?". I know there's a way to step into or over each series of etests and end up where you can reset stored codes but I can't find it.

The 2001 dash display is much more informative and verbose than the earlier models which are kind of cryptic.