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JimsJeep321 06-05-2011 07:40 AM

Idiot lights... perform service.
1991 Jeep Wrangler
4.0 5spd 4x4

I just bought it and and now one of the idiot lights came on in the dash. It says something like "perform service."

1. What service is it recommending??

2. Does my jeep have a computer?? If so where can I plug in a scanner to figure out what the problem is or reset the warning.

thanks everybody!

94impactyj 06-05-2011 10:54 AM

Yes it has a scan port located under the hood by the master cylinder. It is a squaring plug with a black cover over it.

JimsJeep321 06-05-2011 04:43 PM

Are you sure??
I can't find anything that even remotely resembles it. Are you sure it's found next to the master cylinder and is a loose wire with a cover over it??

94impactyj 06-05-2011 05:19 PM

It's on the wire harness. Look for a plug that's not plugged into anything.

Tyewilly 06-05-2011 07:58 PM

2 Attachment(s)
Here's a couple pics of the connector on my '95 2.5L. One plugged into the cap, one exposed. It is hooked to the wiring harness for the computer.

JimsJeep321 06-10-2011 12:44 PM

What type of interface??
Thanks TYEWILLY, I actually found "that" cable but assumed it was AirConditioning related because the interface doesn't match any cables that came with my scanner. Do you know what the interface is called? Is it a SCI???

I'm assuming I need one of these. Actron CP9129 AutoScanner SCI Cable Kit: Automotive

Jeep_Geek 06-10-2011 12:52 PM

I may be wrong but with OBD1 cant you just use the light flashing counting method then look up the code? instead of buying a scanner

Jeep_Geek 06-10-2011 12:53 PM

This may be worth a try

Diagnostic Codes
From the Chrysler FAQ

Start with the ignition off. Within five seconds, switch the key on,
off, on, off, on. (On is not start!)

The "check engine" light will flash. Count the flashes
Each code is a two digit code, so a (for example) 23 would be

It will never flash more than 9 times, watch for pauses!

55 is end of codes, 33 is normal if you dont have air conditioning.

Please note that some codes are NOT included below, this
is not a complete listing, but it IS very close to complete.

88 Start of test (This only appears on DRBII, it's not blinked out)
11 No ignition reference signal detected during cranking (bad hall
OR timing belt skipped one or more teeth; or intermittent
loss of either camshaft or crankshaft position sensor
12 Memory Standby power lost (battery cable disconnected)
13* No change in 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
27 TBI injector does not respond properly to control signal
31 Evaporator Purge solenoid circuit open or shorted OR
Evaparator solenoid circuit
32 EGR system failure OR
Power loss lamp open or shorted
33 Air conditioning clutch relay circuit open or shorted
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
37 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
42 Z1 voltage missing when autoshutdown circuit energized (whatever
that means)
43 Peak primary coil current not achieved with max dwell time
43 Cylinder misfire
43 Problem in power module to logic module interface
44 No FJ2 voltage present at logic board
44 Logic module self-diagnostics indicate problem
44 Battery temperature out of range (see Note #1!)
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
51 Internal logic module fault ('84 turbo only)
52 Oxygen sensor stuck at rich position
52 Internal logic module fault ('84 turbo only)
53 Logic module internal problem
54 No sync pickup signal during engine rotation (turbo only)
54 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

* Activates Power Limited/Check Engine light.

These codes cover multiple years and engines (2.2l, 2.5l,
3.0l). NOTE #1. The power module has an air-cooled resistor which
is used to sense the incoming air temperature. This information
is fed to the logic module and is used to control the duty cycle
of the field current in the alternator. This code applies ONLY
to alternators whose voltage is computer regulated. The battery
voltage is sensed by the logic module -- there is an internal
takeoff from the wire feeding the NVRAM keep-alive power circuit
which is fed to a voltage comparator. So...if you lose the feed
to keep RAM information stored when the engine's off, you also
lose battery voltage sensing.

JimsJeep321 05-14-2013 07:18 PM

It turns out it is the-
33 Air conditioning clutch relay circuit open or shorted

Problem is... my car never came with a/c. The previous owner says that the local Jeep dealer replaced the motor with a crate motor 40k miles ago, so that may be the problem. I've tried clearing out the problem to no avail.
I've learned to live with the red light. Although I may accept defeat this summer and pull the little light bulb.
Thank you everybody for your assistance.

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