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) |
| 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 |
| 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 |
| 37 |
Shift indicator light failure, 5-speed OR part throttle lock/unlock solenoid driver circuit (87-89) OR solenoid coil circuit (85-89 Turbo I-IV) 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 |
| 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) |
