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Moduhrater
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809 Posts
Discussion Starter #1 (Edited)
Just thought this should be included on wranglerboard!

This applies to Jeeps with On Board Diagnostics 1 (1991-1995 in YJs)
First, if you do not have a DRBII scanner you can easily do the "key trick." The on-board reporting will communicate trouble codes to you through the check engine light in a series of flashes; similar to Morse Code.

The key trick: With the ignition OFF, turn the key to ON (do not start the jeep), OFF, ON, OFF, ON (Complete this sequence in under 5 seconds). Be sure to leave the key in the on position until the END OF CODES sequence has flashed (55)

Once the Check Engine Light has turned off, it will pause in the off position for a second or two, and then start to flash, count the flashes. Each code stored will be given to you in a 2 digit sequence. As an example, code 43 would be FLASH FLASH FLASH FLASH... <PAUSE>... FLASH FLASH FLASH followed by a <LONG PAUSE>, followed by the next code. There will never be more than 9 flashes without a pause, and finally Code 55 signals the end of stored codes. Repeat the key trick if you were unsure of a code.

Quick Note: Code 12 is a very common code, and indicates the battery has been disconnected within the last 50 startups. Code 33 will always be present for jeeps without air conditioning. Neither of these codes will themselves cause a check engine light to be displayed.


List of codes/standard meanings:
11: No ignition reference signal detected during cranking (bad hall effect) OR timing belt skipped one or more teeth; or intermittent loss of either camshaft or crankshaft position sensor
12: Memory Standby power lost (Battery or computer recently disconnected)
13: No change in Manifold Absolute Pressure sensor (MAP) from start to run
14: MAP sensor circuit open or shorted; voltage too low
15: No speed/distance sensor signal
16: Loss of battery voltage detected with engine running
17: Engine stays cold too long (bad thermostat)
21: Oxygen sensor signal out of range, possibly shorted
22: Coolant sensor signal out of range (or disconnected to set timing)
23: Intake air temperature signal out of range
24: Throttle position circuit out of range
25: Automatic Idle Speed (AIS) motor driver circuit shorted or target idle not reached, vacuum leak found
26: Peak injector circuit voltage has not been reached
27: Logic module fuel circuit internal problem or TBI injector does not respond properly to control signal
31: Evaporator Purge solenoid circuit open or shorted or Evaporator solenoid circuit
32: EGR system failure or Power loss lamp open or shorted
33: Air conditioning clutch relay circuit open or shorted ( Also will show up for rigs without AC)
34: Speed control vacuum or vent solenoid circuits open or shorted
35: Cooling fan relay circuit open or shorted
36: Wastegate control circuit open or shorted
37: Shift indicator light failure, 5-speed (blown bulb) OR Park/neutral switch failure OR Torque converter unlock circuit open or shorted, A-413 4-speed auto
41: Alternator field control circuit open or shorted
42: Automatic shutdown relay circuit open or shorted
42: Fuel pump relay control circuit
42: Fuel level unit - no change over miles OR Z1 voltage missing when auto shut-down circuit energized
43: Peak primary coil current not achieved with max dwell time OR Cylinder misfire
43: Problem in power module to logic module interface
44: No FJ2 voltage present at logic board OR Logic module self-diagnostics indicate problem OR Battery temperature out of range
45: Turbo boost limit exceeded (engine was shut down by logic module)
46: Battery voltage too high during charging or charging system voltage too low
47: Battery voltage too low and alternator output too low
51: Oxygen sensor stuck at lean position OR Internal logic module fault ('84 turbo only)
52: Oxygen sensor stuck at rich position OR Internal logic module fault ('84 turbo only)
53: Logic module internal problem
54: No sync pickup signal during engine rotation (turbo only) OR Internal logic module fault ('84 turbo only)
55: End of codes
61: "Baro" sensor open or shorted
62: EMR mileage cannot be stored in EEPROM
62: PCM failure SRI mile not stored
63: Controller cannot write to EEPROM
64: Catalytic converter efficiency failure
65: Power steering switch failure
 

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Internet Owner
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9,510 Posts
Great info. Thanks. Glad my '88 doesn't have a computer. Well.... one that's hooked up anyway.
 

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Premium Member
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660 Posts
Diagnostic stuff makes for good stickies... :D
 

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Registered
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29 Posts
21 code twice

Sorry to kick this post up. But can somebody explain to me why I am getting the 21 code twice in the code diagnostic? :confused:

Thanks!
 

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Registered
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1 Posts
we have code 12 42 the engine start crank but do not rubing
put starting fluid and start and runing good. Continuing runing

But wen initiating the ingine do not start.
 

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Jeeper
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1 Posts
Ok so i do the "key trick" and this is what i get. 12, 13, 1, 33, 55. i understand everything but the 1. here is what I'm looking at…

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Premium Member
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1,719 Posts
The numbers will progressively get higher, so you need to confirm the "1" because it is out of sequence.
 

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Registered
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this has been great help !!!! got codes that make some sense to symptoms - especially as most auto electrical companies say my 93 wrangler TOO old for their equipment !!
 
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