No computer is needed for this year of vehicle. There is a sequence (which I can't recall - sorry) where you click the ignition key and count the blinking check engine light on the dash. Most auto parts stores like Shucks, Kragen, etc. will read the codes for free so they can sell you the repair parts.
turn the key on and off 3 times and count the check engine flashes
if you disconnect the battery for at least 5 minutes then reconnect it ,it will reset the check engine light
After reading the code, and repairing the codes, you reset code with a scan tool.
it is the completion of the codes
Everything is set by the computer. If its not idleing right it is probably a throttle body sensor or a idle control sensor or a number of other things. You need to have it hooked up to the computer to check the codes.
The related link below gives the trouble codes for a 1995 grand voyager.
Turn the ignition key off and on three times. You will see the check engine light go off and on. Count the times the light goes off and on. Those are the codes.
Per code manual P0700 is Trans control system malfunction. You need to have the transmission computer checked for codes.
Either with a scanner, or cycle key on, off,on,off,on. and count the flashes of the check engine light. three pause three would be 33
55 is end of message. It just means that the test is done and there are no more codes.
The code numbers are two didgit codes. That was probably a 12 and a 55. 12 is start of message, 55 is end of message. Basically that means there are no trouble codes.
Trouble code 26 in a 1991 Plymouth Acclaim is >>> the Peak Injector circuit voltage has not been reached (need to check computer signals, voltage regulator injectors.) Note: check computer connections! For further ECU codes check out http://www.freeautomechanic.com/diagnostictroblecodes8.html (freeautomechanic.com)