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Old 11-09-2010, 07:13 PM   #1
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check engine light

i have a 94 yj and the check engine light comes on every day after i drive about 1 min no one has anything the check it what could it be??

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Old 11-09-2010, 07:28 PM   #2
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I have a '95... we don't have OBD???

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Old 11-09-2010, 07:44 PM   #3
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Quote:
Originally Posted by tbowden91 View Post
i have a 94 yj and the check engine light comes on every day after i drive about 1 min no one has anything the check it what could it be??
This should help!

Diagnostic Trouble Codes
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Old 11-09-2010, 07:45 PM   #4
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is that y it clears??
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Old 11-09-2010, 07:47 PM   #5
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Diagnostic Trouble Codes

for '95 XJ/YJ and probably most other OBD-era Jeeps

When a late-model, computerized Jeep is having engine problems, one of the ways it communicates these problems back to the driver is to turn on the "check engine" light on the dash. One idiot light isn't very descriptive, so Jeep also privided a method to query the computer for all codes that have been set. Some of these codes are important enough to turn on the check engine light, while others are minor enough not to require immediate attention and therefore will not turn on the dashboard light by themselves.

To query and OBD-I-era computer for these codes, put the key in the ignition and turn the key to run (not start), then off, then run, then off, then run (that's 3 runs and 2 offs). Leave the key in the run position. The check engine light will turn on for a few seconds, then turn off, then (sometimes after 20-30 seconds) start flashing. The flashes are counting out 2-digit trouble codes. Fast flashes count up each digit, with a longer pause between digits. On TJ's with a digital odometer, the code numbers are printed on the odometer in addition to flashing the check engine light. 55 indicates the end of all codes. Once you've got your code list, consult the table below to see what they mean.

OBD-II information is more complex, so the codes for 1998 and newer Jeeps can't be displayed by flashing the check engine light. However, those vehicles which have digital odometers will display the codes on the odometer. I've verified this personally on a 1999 WJ. For those vehicles without digital odometers, or for anybody who wants an English description rather than just a numeric code, an OBD-II code scanner ($100-300) can be plugged in under the dash. OBD-II codes can be looked up online here.

These codes were taken from the '95 XJ/YJ factory service manual.

Code Description
11* No crank reference signal detected during engine cranking.
12* Direct battery input to PCM was disconnected within the last 50 key-on cycles.
13** No difference recognized between the engine MAP reading and the barometric (atmosphereic) pressure reading at start-up
14** MAP sensor input below minimum acceptable voltage.
or
MAP sensor input above maximum acceptable voltage.
15** No vehicle distance (speed) sensor signal detected during road load conditions.
17* Engine coolant temperature remains below normal operating temperatures during vehicle travel (thermostat).
21** Neither rich nor lean condition detected from the oxygen sensor input.
or
Oxygen sensor input voltage maintained above the normal operating range.
22** Engine coolant temperature sensor input above maximum acceptable voltage.
or
Engine coolant temperature sensor input below minimum acceptable voltage.
23** Intake manifold air temperature sensor input above maximum acceptable voltage.
or
Intake manifold air temperature sensor input below minimum acceptable voltage.
24** Throttle position sensor input above maximum acceptable voltage.
or
Throttle position sensor input below minimum acceptable voltage.
25** A shorted condition detected in one or more of the idle air control motor circuits.
27* Injector #1 output driver does not respond properly to the control signal.
or
Injector #2 output driver does not respond properly to the control signal.
or
Injector #3 output driver does not respond properly to the control signal.
or
Injector #4 output driver does not respond properly to the control signal.
or
Injector #5 output driver does not respond properly to the control signal.
or
Injector #6 output driver does not respond properly to the control signal.
33* An open or shorted condition detected in the A/C clutch relay circuit.
34* An open or shorted condition detected in the speed control vacuum or vent solenoid circuits.
or
Speed control switch input below the minimum acceptable voltage.
or
Speed control switch input above the maximum acceptable voltage.
35* An open or shorted condition detected in the radiator fan relay circuit.
41* An open or shorted condition detected in the generator field control circuit.
42* An open or shorted condition detected in the auto shutdown relay circuit.
44* An open or shorted condition exists in the engine coolant temperature sensor circuit or a problem exists in the PCM's battery temperature voltage circuit.
46** Battery voltage sense input above target charging voltage during engine operation.
47** Battery voltage sense input below target charging voltage during engine operation. Also, no significant change detected in battery voltage during active test of generator output.
51** Oxygen sensor signal input indicates lean air/fuel ratio condition during engine operation.
52** Oxygen sensor signal input indicates rich air/fuel ratio condition during engine operation.
53* PCM internal fault condition detected.
54* No fuel sync (camshaft signal) detected during engine cranking.
55* Completion of diagnostic trouble code display on the malfunction indicator lamp (check engine lamp).
62* Unsuccessful attempt to update SRI (service reminder indicator) miles in the PCM EEPROM.
63* Unsuccessful attempt to write to an EEPROM location by the PCM.
* - Check engine lamp will not illuminate at all times if this code was recorded. Cycle ignition key as described and observe code flashed by check engine lamp.

** - Check engine lamp will illuminate during engine operation if this code was recorded.

PCM = Powertrain Control Module (the engine computer)
MAP = Manifold Absolute Pressure (the sensor that measures how hard the engine is sucking air through the intake manifold
EEPROM = Electrically Erasable Programmable Read Only Memory (a type of computer chip used inside the PCM)


Hope this helps i copied from a google search



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Old 11-09-2010, 07:47 PM   #6
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it clears when the jeep is off
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Old 11-09-2010, 08:07 PM   #7
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Clears?
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Old 11-09-2010, 08:39 PM   #8
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the light goes off
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Old 11-09-2010, 08:44 PM   #9
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Quote:
Originally Posted by tbowden91 View Post
the light goes off
it sounds like you are not to familiar with the science behind "The Idiot Light" aka the check engine light, therefore allow us to explain it to you:

read both pages thoroughly and follow the instructions provided and you will have the reason for your engine light (most likely)



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Old 11-10-2010, 09:53 AM   #10
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the codes were 12,21,33,54
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Old 11-10-2010, 12:41 PM   #11
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Quote:
Originally Posted by tbowden91 View Post
the codes were 12,21,33,54
code 12 states that the battery has been disconnected in the last 50 cranks, so i wouldn't worry about that one or the 33. If you don't have A/C then 33 will always pop up, at least is does for me. I would be concerned and check out the other two. Some others may jump in and give some guidance.
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Old 11-10-2010, 02:02 PM   #12
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the codes were 12,21,33,54
Im almost positive 21 can be solved by replacing the 02 sensor, as for 54 i dunno what this is exactly
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Old 11-10-2010, 05:08 PM   #13
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If I'm not mistaken, its in the distributor and can be replaced, but you have to take the distributor apart to fix it. You might be better off getting a rebuilt distributor.
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Old 11-10-2010, 05:25 PM   #14
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Just to be sure you did get the final 55 code and did not miscount a 54 right?
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Old 11-10-2010, 06:06 PM   #15
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Just to be sure you did get the final 55 code and did not miscount a 54 right?
Ohhhhhhh yea good point, it will flash a 55 when it is done reading codes this is not an error.
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Old 11-10-2010, 06:06 PM   #16
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Ohhhhhhh yea good point, it will flash a 55 when it is done reading codes this is not an error.
If you did miscount make sure you go back and count the codes correctly, its important
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Old 11-10-2010, 07:16 PM   #17
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If you did miscount make sure you go back and count the codes correctly, its important

Thats a good point...i usually do it two or three times mainly because i forget and say to myself "shi&t, was that interval long or short???"...lol
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Old 11-11-2010, 06:10 AM   #18
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yea same here
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Old 12-08-2010, 08:42 AM   #19
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hey guys new to this, and any help would be great. I'v got a 94 yj 4 cyl 5sp
and when you first turn the key ahead she wont go, no fuel pump service engine light or throttle body. Now if you leave the key turned on for an hour or so you will suddenly hear the relays start to click, the engine light starts to flash and then after about a min or so the fuel pump turns on the engine light stays on and you can hear the throttle body engage. hit the key and she runs like a champ, you shut her down she'll bang right up but if you leave it for a 10 minutes or so then you gotta wait again to start it. Any ideas on what might be wrong would be a big help, im not to sure of my way around a jeep YET. thanks
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Old 12-10-2010, 04:28 PM   #20
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My thought would be a bad battery. In the future I'd reccomend just starting a new thread rather than tack something like this on to an older thread
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Old 12-11-2010, 02:47 AM   #21
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can allways take it to autozone or advance auto and have them check it out too;;;;;
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Old 12-11-2010, 07:03 AM   #22
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can allways take it to autozone or advance auto and have them check it out too;;;;;
I wouldnt even buy an air freshener or tire guage at AutoZone.
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Old 12-11-2010, 10:36 AM   #23
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OK, Both me and my wifes Jeep (92 & 94 YJ's 2.5 5 speeds) Both are giving a code for the AC clutch relay, but neither vehicle has AC?
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Old 01-12-2011, 07:34 PM   #24
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the jeeps that were made had a program in the computer to read if that switch or clutch switch went bad to better troubleshoot a/c..87-95 . it woulda been to expensive in that time frame to redesign an ecu and its rom program to not display this error with the many jeeps that were and were not made with a/c. additional programming and parts cost and r&d gets VERY expensive, so they stuck with a universal design, on our end, the parts are cheaper because of this theory, and like a chevy, you can swap aything in or out, if you cant, find a spacer or five a shim here and their and or a crudely made bolt pattern plate adapter and it works..

as far as I know, A/C was an addon some years later that you had to request to get. cherokes and grands in those years also used the same powerplants to...in some cases even the same wireing harnesses..

i couldn't of said it better, but their was a jeep in a boneyard (junkyard) and a guy saw me takeing stuff out so easily, and made the comment to his friend:

"Jeeps are like legos for grown up, everything on them is interchangable"
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Old 07-02-2011, 11:41 AM   #25
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my ac clutch relay and battery disconnect are the only things coming up on the check engine warning. Problem is jeep wont start wont idle. If i do get it started, it backfires and will not accelerate! wtf! I replaced the vacuum switch on the np231 transfercase, but obviously thats not it. what to do what to do!!!!!!!!!!!!!!
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Old 09-09-2012, 09:46 AM   #26
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Code 41

All,

My check engine light will turn on after about 2 minutes of driving as well. The codes I get are 12,33,42,55. I'm concerned about the 41. Does anyone know what that really means and how to fix it?

Thanks, Norm5968
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Old 10-09-2012, 09:49 PM   #27
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DTC-41. Is your alternator charging? hook up charge tester or go to a parts store or garage and have them do an Alt test for you. should be charging at 14-14.2 volts with your head lights on hi and your heater blower motor on hi. If no or bad charging, brushes in alt. are prob. sticking or to worn down. 55 is what the guys up top said its the code indicating end of code list
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Old 03-14-2013, 08:35 PM   #28
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Thanks, good info !! Previous 78' CJ/304 owner with a 94' YJ 4.0 now (You could say "Lost" lol). Just purchased recently. This is very helpful and much appreciated. This forum is a College/University for Jeeps from what I see so far, thanks to people like you for taking the time to post it.
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Old 03-07-2014, 10:20 PM   #29
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This is a great forum! People seem much more helpful and friendly here than other forums I've been on.

In case someone stumbles across this tread in search for "how to run trouble codes". I just would like to add the video I created to help someone\everyone out!


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