TJ Computer Error Codes

Experiencing a check engine light on your Jeep Wrangler TJ? Get your hands on a diagnostic code reader and see what it’s saying. Code readers can usually be borrowed or rented from local auto parts dealers.

11 No ignition reference signal detected during cranking (bad Hall effect) OR timing belt skipped one or more teeth; OR loss of either camshaft or crankshaft position sensor. Can cause the engine to stop
working entirely with no limp-home mode.
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?)
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, vacuum leak found
26 Peak injector circuit voltage has not been reached (need to check computer signals, voltage reg, injectors)

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
32 EGR gases not working – check vacuum, valve
32 (1990-92, all but Turbo) 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)
34 (1984-86) EGR solenoid circuit shorted or open
34 (1987-1991) speed control shorted or open
35 Cooling fan relay circuit open or shorted
35 (trucks) idle switch motor fault – check connections
36 (turbo) Wastegate control circuit open or shorted
36 (3.9/5.2 RWD) solenoid coil circuit (air switching)
36 (Turbo IV) #3 Vent Solenoid open/short

Shift indicator light failure, 5-speed


part throttle lock/unlock solenoid driver circuit (87-89)


solenoid coil circuit (85-89 Turbo I-IV)


Trans temperature sensor voltage low (1995 and on)

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 autoshutdown circuit energized
43 Peak primary coil current not achieved with max dwell time OR 43 Cylinder misfire OR 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 (Bob wrote: may be tripped by a bad EGR system causing a rich condition, and the O2 sensor trying to compensate. The O2 sensor may still be good. The EGR assembly
consists of two pieces, the valve and the vacuum transducer (round plastic unit with cylinder on top and both electrical and vacuum connections) 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) – or camshaft sensor/distributor timing (7)
55 End of codes
61 “Baro” sensor open or shorted
62 EMR mileage cannot be stored in EEPROM OR PCM
failure SRI mile not stored
63 Controller cannot write to EEPROM
64 Catalytic converter efficiency failure
65 Power steering switch failure
88 Start of test (not usually given, don’t expect it)