On a 1993 you turn the key to the on position to the off position 3 times. On the 3rd time leave it in the on position and count the flashes on the check engine light. Use a haynes manual to check what the number code is eg. 3 flashes pause 5 flashes is 35. Auto zone will help you find what you need.
1990 will require an OBD1 reader
p0141 is for the sensor behind the catalytic converter.
http://www.instant-radio-code.co.uk/chrysler-jeep-code-search.php
Diagnostic code 43 in the 1997 Jeep Grand Cherokee refers to an issue with the distributor. This often causes the Jeep to stall at operating temperature.
In order to use a code reader on a 1992 Dakota simply plug it into the DLC outlet. From there, the code reader should properly function.
http://www.jedi.com/obiwan/jeep/dtc.html
Error code 66 on a 1997 Jeep Cherokee means TCM to PCM failure. This code means that the transmission control model is not communicating with the powertrain control model.
O2 sensor or wiring
catalytic converter circuit
Cylinder #1 misfire.
Throttle position sensor out of range.
Trouble code P0700 means:Transmission control system malfunction