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gary1 02-01-2006 09:11 AM

95 YJ 2.5L - Check Engine Light on when starting cold
I know I could go to the dealership and have the code read, but I thought maybe somebody could tell me right up front what my problem is.
The Check Engine light comes on when the Jeep starts up cold. After it warms up a little bit the light won't come on when started.
It seems to run good even with the light on. I'm hoping its just a simple sensor, or something along those lines.
Thanx in advance for any response.

Lighting Guy 02-01-2006 09:47 AM

This is taken from the FAQ pinned at the top:

Self-diagnostic codes can be obtained from your 91-95 YJ by simply inserting the key into the ignition. Turn the key to the on position (when the lights on the dash come on) then off, on, off, and on. It has been said that you need to go through key cycle in less than 5 seconds.
Now that you have cycled the key on, off, on, off, on, the check engine light will begin to flash. One flash a short pause and two flashes indicates a code 12, three flashes, a short pause, and three flashes indicate a code 33. There will longer pauses between codes when there are multiple fault codes.
If your check engine light will not come on it's fairly common that it's because the bulb is burned out. In that case just remove the guage cluster and replace the CEL bulb with the bulb for the seatbelt reminder.

When you determine what codes are stored in the computer you must disconnect the battery for a minute or so after you have completed the repair so that the code will be erased from the computers memory. If you don't do it the motor will still run badly because the computer will still think there is a problem even though the check engine light is not on.

Here are the codes as listed in Chiltons.

11 No crank reference signal at PCM

12 Battery disconnect

13 No change in MAP from start to run

14 MAP sensor voltage too low or too high

15 No vehicle speed (distance) sensor signal

17 Engine is cold too long (thermostat stuck open)

21 O2S stays at center or O2S shorted to voltage

22 ECT sensor voltage too high or too low (engine coolant temperature sensor is faulty)

23 Intake air temp sensor voltage too low or too high

24 Throttle position sensor voltage too high or too low

25 Idle air control motor circuits

27 Injector control circuit

33 Air conditioning clutch relay circuit

34 Speed control solenoid circuit or switch voltage

41 Generator field not switching properly

42 Auto shutdown relay control circuit

44 Battery temp sensor volts out of limits

46 Charging system voltage too high

47 Charging system voltage too low

51 O2S signal stays below center (lean)

52 O2S signal stays above center (rich)

53 Internal PCM failure or PCM failure SPI communiations

54 No cam sync signal at PCM

55 Completion of diagnostic code display

62 PCM failure SPI miles not stored

63 PCM failure EEPROM write denied

gary1 02-02-2006 01:38 PM

process you described, and my code is 33 (Air Conditioning Clutch Relay Circuit).
Considering the fact that I don't have AC in my jeep is there something else I should know about this code.

blake989 02-02-2006 01:58 PM

something may be screwing with the light or pcm itself, it should come on when started, cold or hot. Does it stay on until it is warmed up? Does it come on while starting warm and just go right off? Also, no don't worry about the code 33.

jeepmud 02-02-2006 08:08 PM

i have a 94 2.5 and it use to stumble and the check light was on. after i put the 4.0l throtlle body on i havnt had a problem

finwrangler 02-02-2006 11:24 PM

I recently started topic for error code 33, and after some comments we were to come to conlusion that without a/c equipped YJ:s all give that code, because of the open relay for bolt-on a/c. It seems its easier to build a vehicle with wiring for all possible options, then just bolt those options on that the buyer has ordered...

But my YJ gave 12,33,55. I suppose you got those too (although 12 and 55 arent actual trouble meaning codes)?

Could it be that the a/c open relay is somehow pointed for example upwards and its frozen for small snow particles flying when you drive- and then melted into it when engine has warmed up. -- and then giving the code 33.

gary1 02-03-2006 02:40 PM

My check engine light comes on momentarily when starting the jeep which it should. I doesn't stay on, but when checking the code I did get the 12,33,55 sequence that you mention. I guess for now I'll just assume nothing is wrong.
I runs perfectly, so I don't think it has any effect on anything. It just wondered what might be happening.
Thanx for all the info...

95 jeeper 02-03-2006 07:10 PM

My check light comes on everytime it rains or is moist out. After I drive for a few minutes and start it again it is always off so ifigure it is a sensor getting a little wet. As long as it goes out and the codes don't change I don't worry about it. My .02

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