How do I get Check Engine Light codes (OBD-I) from a '94 Jeep Grand Cherokee, and where can I look them up?
This blog is a nice reference:
It explains how to check:
Within a period of 5 seconds, cycle the ignition keyON-OFF-ON-OFF-ON.
Count the number of time the MIL (check engine lamp)on the instrument panel flashes on and off. The number of flashes represents the trouble code. There is a short pause between the flashes representing the 1st and 2nd digits of the code. Longer pauses are used to separateindividual 2-digit trouble code.
An example of a flashed DTC is as follows:
-Lamp flashes 4 times, pauses, then flashes 6 more times. This denotes a DTC number 46. -Lamp flashes 5 times, pauses, then flashes 5 more times. This indicates a DTC number 55. DTC 55 will always be the last code to be displayed.
And has a list of codes:
88 display used for start or test 11 camshaft signal or ignition signal, no reference signal during cranking 12 memory to controller has been cleared within 50-100 engine starts 13 map sensor not detecting any change during test 14 map voltage too high or too low 15 vehicle speed sensor, no signal detected 16 knock sensor circuit. open or short detected 17 low engine temperature, possible thermostat fault 21 oxygen sensor signal, neither rich or lean detected 22 coolant sensor voltage low 23 air charge voltage high/low detected 24 throttle positioner sensor voltage high/low 25 automatic idle speed motor driver circuit, short or open detected 26 injectors 1,2,3 peak current not reached 27 injector control circuit does not respond to control signal 31 purge solenoid circuit, open or short detected 32 egr solenoid circuit, open or short detected 33 a/c clutch relay circuit, open or short detected 34 speed control servo solenoid, open or short detected 35 radiator fan control relay circuit, open or short detected 36 wastegate solenoid, open or short detected37 part throttle unlock(PTU) circuit, open or short detected 41 charging system circuit not responding to control signal 42 fuel pump or auto shutdown (ASD) relay voltage sensed at controller 43 ignition control circuit not responding 44 battery temperature voltage circuit problem 45 turbo boost limit exceeded-map sensor detects overboost 46 battery voltage too high 47 battery voltage too low 51 air/fuel at limit 52 logic module fault 53 internal controller failure 54 camshaft reference circuit not detected 55 end of message 61 baro read solenoid, open or short detected 62 emr mileage not stored 63 eeprom write denied 64 flex fuel sensor signal out of range 65 manifold tuning valve, open or short detected 66 no ccd messages 76 ballast bypass relay, open or short detected 77 speed control relay, open or short detected
Once you have the code you probably could search online if this list is not complete.