This may help-
"With the new Mopar MPI fuel injection system comes a new computerized emissions control system. This system, as with all 1991 and later models, is equipped with a self-diagnosis function that stores codes in the computer that can later be retrieved. The codes will direct you toward an area, or function, in the motor's system that is "reporting" a problem. The report will come to you via the Check Engine light that you should install with your Mopar MPI system. Some Jeeps (that came from the factory with their fuel injection system) will have a POWER LOSS light on the dash, this is the same thing as the "check engine" light.
To retrieve the "trouble codes" from the Check Engine light, the manual recommends first cycling through most of the functions in your system. By this, you should start the Jeep and put the transmission in Park (automatic) or Neutral (manual). Next, raise the engine speed to around 2500 RPM and slowly let the engine speed drop down to idle. If your Jeep is so equipped, turn on your air conditioning briefly then shut it off. Last, if you have an automatic transmission, with your foot on the brake, select each position on the transmission and bring the shifter back to park. Then turn the motor off.
To display the codes, turn the ignition key ON, OFF, ON, OFF, and finally ON. Don't turn the key to the START position, just switch it to the ON position! The codes will begin to flash on the Check Engine light or the Power Loss light. The codes are always two digits, and the last code always displayed is a 55. So if you follow this procedure and you only get a 55, that means there are no codes being reported. The Check Engine light will blink the number of the first digit then pause, and then blink the second digit. There is about a 2-second delay between the first and second digits. If there is more than one set of codes being displayed, the pause between codes will be about 4 or 5 seconds."
Code ----------- Probable Cause
11 Ignition
12 Battery or computer recently disconnected
13 Manifold Absolute Pressure (MAP) sensor vacuum
14 Manifold Absolute Pressure (MAP) sensor electrical
15 Distance sensor or circuit
16 Loss of battery voltage detected with engine running
17 Engine running too cool
21 Oxygen sensor or circuit
22 Coolant temperature sensor or circuit
23 MAT sensor or circuit
24 Throttle Position Sensor (TPS) sensor or circuit
25 Automatic Idle Speed (AIS) circuit
26 Peak injector circuit voltage has not been reached (need to check computer signals, voltage reg, injectors)
27 Fuel injector control
33 Air conditioning clutch relay
41 Alternator field
42 Automatic shutdown relay
44 Battery temperature sensor
46 Battery over voltage
47 Battery under voltage
51 Oxygen sensor - lean condition indicated
52 Oxygen sensor - rich condition indicated
53 Internal engine controller fault
54 Distributor sync pickup
55 End of Code Output
62 Emissions Maintenance Reminder (EMR) mileage accumulator
63 Controller failure EEPROM write denied
