I have a 1997 Cherokee Sport automatic transmission with 4wd. The check engine light keeps coming on, showing the same code 12, 45, 55. The first few times it came on I switched cars for a few days. My mom would drive it for a few days, only for her to have no trouble and for the light to turn off. I have only had symptoms once with the lights, where the car was hesitating and the RPM's were much higher, and the car was not shifting properly, otherwise every other time it has been just a light with no symptoms. Does anyone have any ideas? Thanks!

Take it to auto zone... They should do a free "check engeine light" service. If they are the same codes that pop up when they check it, then have them look up what those codes are.

Hope this helps the 12 is the bad one especially if you have not disconnected the battery :
Code Description
11 No crank reference signal detected during engine cranking.

Intermittent loss of either camshaft or crankshaft position sensor.

CKP sensor target windows have too much variation.
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 (atmosphere) pressure reading from start-up.
14 MAP sensor input above or below acceptable voltage.

5 volt output to MAP sensor open.
15 No vehicle speed sensor signal detected during road load conditions.
17 Engine did not reach operating temperature within acceptable limits.

Engine does not reach 20º F. within 5 minutes with a vehicle speed signal.
21 Upstream oxygen sensor response slower than minimum required switching frequency.

Upstream oxygen sensor heating element circuit malfunction.

Downstream oxygen sensor heating element circuit malfunction.

Downstream oxygen sensor input voltage maintained above the normal operating range.

Oxygen sensor voltage too low, tested after cold start. (Upstream or Downstream)

Left oxygen sensor input voltage maintained above the normal operating temperature.
22 Engine coolant temperature sensor above or below acceptable voltage.
23 Intake air temperature sensor input above or below acceptable voltage..
24 Throttle position sensor input above or below acceptable voltage.

TPS signal does not correlate to MAP sensor.
25 A shorted or open condition detected in one or more of the idle air control motor circuits.

Actual idle speed does not equal target idle speed.
27 Injector 3, and/or 4, and/or 5, and/or 6 output driver does not respond properly to the control signal.
31 An open or shorted condition detected in the A/C clutch relay circuit.

Insufficient or excessive vapor flow detected during evaporative emission system operation.
33 An open or shorted condition detected in the duty cycle purge solenoid circuit.
34 An open or shorted condition detected in the Speed Control vacuum or vent solenoid circuits.

Speed control switch input below the minimum acceptable voltage.
37 Relationship between engine speed and vehicle speed indicates no torque converter clutch engagement. Auto. only.
37 An open or shorted condition detected in the torque converter part throttle unlock solenoid control circuit. (3 speed auto RH trans. Only).

Incorrect input state detected for the Park/Neutral switch. Auto. only.
41 An open or shorted condition in the generator field control circuit.
42 An open or shorted condition detected in the auto shutdown relay circuit.

An open condition detected in the ASD relay output circuit.

An open or shorted condition detected in the fuel pump relay control circuit.

An open circuit between PCM and fuel gauge sending unit.

Circuit shorted to voltage between PCM and fuel gauge sending unit.

No movement of fuel level sender detected.
43 Peak primary circuit current not achieved with maximum dwell time.
43 Misfire detected in one or more cylinders 1 thru 6. (4 and 6 cyls.)
44 Battery temperature sensor in voltage above or below acceptable range.
46 Battery voltage sense input above target charging voltage during engine operation.
47 Battery voltage sense input below target charging during engine operation. Also, no significant change detected in battery voltage during active test of generator output circuit.
51 A lean air/fuel mixture has been indicated by an abnormally rich correction factor.
52 A rich air/fuel mixture has been indicated by an abnormally rich correction factor.
53 PCM Internal fault condition detected.
54 No camshaft signal detected during engine cranking.
55 Completion of fault code display on Check Engine lamp.
63 Unsuccessful attempt to write to an EEPROM location by the PCM.
64 Catalyst efficiency below required level. (Same as code 72)
65 Power steering high pressure seen at high speed. (2.5L only)
72 Catalyst efficiency below required level. (Same as code 64)
77 Malfunction detected with poser feed to speed control servo solenoids

u helped me with a problem and u didn't even know it thanks. new member xjman98.

I get code 45 on my 97 Cherokee and I can't find anybody or anything in black & white to tell me what that code is....any ideas?

A '97 has OBDII...get the code(s) read with a reader/scanner.

OBD I Code 45 is "Transmission OD solenoid circuit failure. Open or short in the transmission overdrive solenoid circuit."

As belvedere stated, your '97 is OBD II XJ. It has both the ability to retrieve Diagnostic Trouble Codes using the key trick and using a code reader/scanner at the Data Link Connector.

The ’97 FSM does not list a cross reference from OBD I code 45 to an OBD II code. In fact, the ’97 DTC listing shows very few OBD codes.

Generally, a '97 37 code translates to P0740/743 OBD II codes, which are Torque Converter solenoid problems.

Have your DLC scanned and get the exact code number.

Thanks for the very informative follow-up.

I did get it scanned at Auto Zone and it was the tranny, thanks for the info. guys!