all the radios have there own codes you will need to get it recoded at your local dealer The factory radio did not use theft codes.
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.
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
Throttle position sensor out of range.
Cylinder #1 misfire.
catalytic converter circuit
Trouble code P0700 means:Transmission control system malfunction
Through radiocodeking.co.uk/jeep-radio-codes and their great offer, you can get the radio code for free. All you have to do is put the radio serial and the voucher code: freejeepcode upon the checkout page (making it free).
how to fix or check po 206
1990 will require an OBD1 reader