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Old 10-30-2012, 12:16 PM   #1
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Need some help to read error codes

Hi every one i have zero idea about reading ecu error codes so this is a small clip of the errors showing in my 91 yj


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Old 10-30-2012, 12:49 PM   #2
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12- Battery disconnected recently
21-oxygen sensor or circuit
33-Air conditioning clutch relay ( I dont have ac, but get this code)
35=Cooling fan circuit or idle switch motor fault
thats all I could see, but your video i think was cut short

Hopefully someone else will chime in if they think my flash count was wrong

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Old 10-30-2012, 02:03 PM   #3
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Thats a lot off errors :-)
I will try to record a longer clip and start troubleshooting the errors one by one.
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Old 10-30-2012, 02:08 PM   #4
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Mega, when the codes are done, the dash will flash five times, then another five times for a code of "55"
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Old 10-30-2012, 02:12 PM   #5
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How i can read those codes cuz there is two flashing a long and short one.
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Old 10-30-2012, 07:22 PM   #6
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Here is the list of codes for your reference, copy to a word document and store in a handy place.

On board diagnostic codes for the YJ are

OBDI for Jeep YJ 1991-1995.
Turn key on/off three times, then on (engine not running), engine light will flash codes. Longer pauses are breaks between codes. Last code will be 55.
Ignore code 33 on non ac YJ's


11 No ignition reference signal detected during cranking OR timing belt skipped one or more teeth; OR loss of either camshaft or crankshaft position sensor.
12 Battery or computer recently disconnected
13 MAP sensor or vacuum line may not be working
14 MAP sensor voltage below .16V or over 4.96V
15 No speed/distance sensor signal
16 Loss of battery voltage detected with engine running
17 Engine stays cool too long (bad thermostat or coolant sensor?)
OR
17 (1985 turbo only): knock sensor circuit
21 Oxygen sensor signal doesn't change (stays at 4.3-4.5V). Probably bad oxygen sensor
22 Coolant sensor signal out of range - May have been disconnected to set timing
23 Incoming air temperature sensor may be bad
24 Throttle position sensor over 4.96V
25 Automatic Idle Speed (AIS) motor driver circuit shorted or target idle not reached
26 Peak injector circuit voltage has not been reached (need to check computer signals, voltage reg, injectors)
27 Injector circuit isn't switching when it's told to (TBI)
OR (MPI) injector circuit #1 not switching right
OR (turbo) injector circuit #2 not switching right
OR (all 1990-) injector output driver not responding
- check computer, connections
31 Bad evaporator purge solenoid circuit or driver
32 (1984 only) power loss/limited lamp or circuit
OR
32 EGR gases not working (1988) - check vacuum, valve
OR
32 (1990-92) computer didn't see change in air/'fuel ratio when EGR activated - check valve, vacuum lines, and EGR electrical
33 Air conditioning clutch relay circuit open or shorted (may be in the wide-open-throttle cutoff circuit or normal on early 80's models if you don't have air conditioning)
34 (1984-86) EGR solenoid circuit shorted or open
OR
34 (1987-1991) speed control shorted or open
35 Cooling fan relay circuit open or shorted
OR
35 idle switch motor fault - check connections
36 (turbo only) Wastegate control circuit open or shorted
37 Shift indicator light failure, 5-speed
OR
part throttle lock/unlock solenoid driver circuit (87-89)
OR
solenoid coil circuit (85-87 Turbo only)
OR
Trans temperature sensor voltage low (1995 and on)
41 Alternator field control circuit open or shorted
42 Automatic shutdown relay circuit open or shorted
OR
42 Fuel pump relay control circuit
OR
42 Fuel level unit - no change over miles
OR
42 Z1 voltage missing when autoshutdown circuit energized (The Z1 voltage is the voltage of the circuits fed by the autoshutdown relay. This typically includes fuel pump and switched-battery feed to the ignition coil)
43 Peak primary coil current not achieved with max dwell time
OR
43 Cylinder misfire
OR
43 Problem in power module to logic module interface
44 No FJ2 voltage present at logic board
OR
44 Logic module self-diagnostics indicate problem
OR
44 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 (this may be tripped by a bad MAP sensor system causing a rich condition. If you get hot rough idle and stalling, especially on deceleration, accompanied by flooded engine and difficulty restarting, that can be a bad MAP sensor causing the O2 sensor to try to compensate. If you get poor cold driveability, stumbling and bucking, and acceptable warm driving with poor gas mileage (a drop of 10 mpg or more), that is usually the O2 sensor.
OR
51 Internal logic module fault ('84 turbo only).
52 Oxygen sensor stuck at rich position
OR
52 Internal logic module fault ('84 turbo only)
53 Logic module internal problem
54 No sync pickup signal during engine rotation (turbo only)
OR
54 Internal logic module fault ('84 turbo only) - or camshaft sensor/distributor timing
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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Old 11-14-2012, 09:36 AM   #7
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^ nice! Thanks!
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Old 11-14-2012, 10:18 AM   #8
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I thought 12 started the codes and 24 finished them
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Old 11-14-2012, 10:28 AM   #9
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Quote:
Originally Posted by nicks_yj View Post
I thought 12 started the codes and 24 finished them
12 is if your bat. was disco'd within the last 12 starts. This also happens IF it cranks to slow and the voltage drops to far during start up. It will think it lost voltage because of the draw to the starter being so high at points.

55 ends the codes.

I have to go back and do mine again, I keep seeing mixed results or Im counting wrong. Looks like have; 12 75 73 35 41 55 not possible? There arn't any in the 70's? Tried again, 12 35 73 35 42 And again; 12 35 33 55

I think Im getting better at reading the flashes lol.

35 Cooling fan relay circuit open or shorted
OR
35 idle switch motor fault - check connections

^35 concerns me. I don't have an electric fan. Maybe thats why I see this one? 33 is ok, I don't have air, thats expected.

Quite honestly, I think my particular problem is related to my starter. It started cranking slow, replaced the old bulged out battery and now I get mixed results. Sometimes she'll spin over fast, other times it cranks slow like to much drag on the starter. The times it cranks slow, the voltage drops to far and tells the ECM there was a battery disconnect.
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Old 11-14-2012, 01:33 PM   #10
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My starter was acting crazy to check the wire going to the starter my connection was bad and I needed a new connector on there
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Old 01-11-2013, 03:44 PM   #11
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I was getting intermitten check engine lights. mostly it would pop on when I hit the gas to go up an on ramp or pass somebody.

I did a tune-up, replaced cap/rotor/plugs/oil change/oil filter & air filter.

She fires right up, runs and drives great. No hesitation, nothing seems out of the ordinary.

Two weeks later, now the light is always on.

My codes read; 1275733542155

now, some seem off as 75 is way high?

Going backwords, knowing it should end w/55 I would have 55, 21, 54, 33, 57, 27, 1

Im reading as; (in reverse order)
55 End of codes
21 Oxygen sensor signal doesn't change (stays at 4.3-4.5V). Probably bad oxygen sensor
54 Camshaft sensor/distributor timing
33 Air conditioning clutch relay circuit open or shorted, OK I don't have air...
57 non-existant?
27 Injector circuit isn't switching when it's told to (TBI)

My plan tonight is to look over all wiring and connections and also wash under the hood. As well, I want to run a can of injector cleaner through it with my next tank of gas.

O2 sensor, I see that listed. Prob. have to get one of those in there to. Maybe CAM Sensor? Any other ideas for stuff I should check? I also know for sure it is not my catalitic convertor. (CAT) so pls don't suggest that.
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Old 01-11-2013, 06:54 PM   #12
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I cleaned and redid the main ground by the coil and replaced the coil w/oem. looked really old, prob. original from 94. Also replaced the plug wires this time around. Throttle seems a little more responsive... Overspill for radiator was a little low, filled that back to the full mark.

picked up an o2 sensor and a new wheel hub to install tomorrow.

So far no CEL but have not driven far at all...
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Old 01-14-2013, 09:32 AM   #13
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2 things were causing me problems and everything is 100% now. I went through a ton of mud yesterday then out on a 25 mile sloppy back road tour w/some really deep puddles. Working flawlessly! and no more sputter through water...

The water sputter had to be related to the coil or the grounds down there.

Aside from that, I think the 02 sensor was tripping the check engine light. It was an inacurate reading, neither reading + or -. Come to find out, just before the 02 sensor where the manifold bolts to the exhaust, the donut was really loose. We locked it down and changed the sensor anyways. Its much quieter now, didn't realize it was so bad until we locked it back down lol.

Needless to say, all is working GREAT! I replaced the following over a few days;

plugs
cap & rotor
plug wires
coil
air filter
oil and oil filter
02 sensor

and we tightened the donut, replaced the front wheel hub, checked all other fluids and checked my tire psi all around. If you are ever concerned about the donut, look for blackness around it. There shouldn't be any. If there is carbon build up, there is a leak.
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Old 01-16-2013, 03:12 PM   #14
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trying not to hijack the thread lol... just sharing in the same place for error code trouble.

Jeeps been great for a few days, until today my stupid CEL came back on.

I pulled codes,

12 - start
21 - Oxygen sensor signal doesn't change (stays at 4.3-4.5V). Already changed it. Maybe donut came lose again??? Will check it tonight
33 - no AC, doesn't matter
41 - Alternator field control circuit open or shorted
46 - Battery voltage too high during charging or charging system voltage too low.

Maybe Alternator? Its still original from 94' I think... 160,000 roughly

55 - end
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Old 01-18-2013, 07:53 PM   #15
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The yj's started obdI in 91? Where is the port for hand held obdI reader?
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Old 05-24-2014, 12:09 PM   #16
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hello, new member here...great to have this forum..i have a 94 yj 4.0 with ac...check engine light pops on occasionally after i've driven it a long time only...it has a miss that i feel at idle...seems to have good power otherwise...i am completely lost on how to read codes or flashes ?..how do you come up with these #s from the flashes ?...any help will be much appreciated
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Old 05-24-2014, 12:26 PM   #17
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Turn the key to on (do not start)
Turn the Key off
Turn the key on (do not start)
Turn the key off
turn the key on (do not start)

Watch the Check Engine light. It will begin to flash. It will have half a second pause between flashes to give you a single digit number with a full second pause between "complete" numbers. Then an even longer pause (about 2 seconds) between whole numbers

A code 55 is ALWAYS end of codes: SO it would go like this:

Flash <.5 pause> Flash <.5 pause> Flash <.5 pause>Flash <.5 pause> Flash <1 second pause> Flash <.5 pause> Flash <.5 pause> Flash <.5 pause>Flash <.5 pause> Flash


Edit: Heres a video on how to do it:
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Old 05-24-2014, 12:30 PM   #18
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Quote:
Originally Posted by RT Kowalski View Post
hello, new member here...great to have this forum..i have a 94 yj 4.0 with ac...check engine light pops on occasionally after i've driven it a long time only...it has a miss that i feel at idle...seems to have good power otherwise...i am completely lost on how to read codes or flashes ?..how do you come up with these #s from the flashes ?...any help will be much appreciated


for a 95:

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
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Old 05-24-2014, 04:17 PM   #19
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thanks everyone...hoping i got this right but i'm coming up with 12...11..51..in that order....any ideas on what to check on these ?...i bought the jeep bout 3 weeks ago, so not sure about any recent battery disconnections..does that mean whether its been started 50 times since a change ?..i've driven it a bit since then...abs light is on too but we've replaced all brakes..not worried about it

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