Code 12 just means that the ECM is going into diagnostic mode, this is NOT a trouble code! Code 12 should blink a couple of times pause then blink your trouble codes if you have any. If you have no trouble codes, it will resume to blink code 12 again.
No you need a hand held scanner,
12 equals battery disconnected recently,43 equals engine misfire(get diagnostic done to find out which cylinder)and 55 means end of codes
12 - battery was disconnected 14 - map sensor volts low 27 - injector control circuit 55 - end of message (no more codes)
The diagnostic code 12 51 55 is actually not a code for the 1994 Jeep Grand Cherokee Laredo. The 12 means that it has started searching for codes. The 51 is oxygen sensor stuck lean. The 55 means it is finished searching for codes. Getting this means nothing is wrong.
Power to the pcm was lost or interrupted.Whenever your battery is disconnected to clear fault codes,code 12 remains in the computers memory,the code is erased automatically after 20-100 key on cycles depending on the year.
That code will flash whenever the diagnostic terminal is grounded with the ignition turned on and engine is not running. If there is additional trouble codes stored in the ECM they will appear after code 12 has flashed 3 times. If you have no other codes that flash. Then code 12 means system is okay and no codes presant.
Code 12 is a period It flashes when the codes start and end so you will see code 12 usually three times, then the codes you need to fix then code 12 three time and the codes you need to fix will repeat and so on.
The diagnostic code P03xx is not specific to one vehicle manufacturer. In fact, most codes starting with a P are not manufacturer specific. In the case of P03xx codes, the P03 indicates the issue is with the ignition system. The xx in this case, assuming it is between 1 and 12 indicate the cylinder in which the problem ocurred. P0305 indicates a Cylinder 5 misfire has been detected. For a complete list of OBD-II Diagnostic Codes, go here: http://www.obd-codes.com/trouble_codes/
DTC code 81, 2-3 shift solenoid circuit fault. DTC code 12, indicates the diagnostic system is working.
Code 55 is end of message ( it is done flashing codes )Code 12 is start of message or battery was disconnected.Code 55 is end of message ( it is done flashing codes )Code 12 is start of message or battery was disconnected.
You need a scan tool. Not necessarily -- By cycling the ignition switch the check engine light will flash to indicate MOST codes. on-off on-off on-off on flash once pause twice (12 - system online) stored code(s) flash 5 times (all codes displayed)