My check engine light is coming on...HELP!

Not the speed sensor , misfire ? plug , plug wire etc..... Check engine light on ? Have diagnostic's done on the vehicle ,check misfire counters on mode 6 . Do you know what this is ? If not your best bet ,take it to a qualified repair shop.

code p0720 refers to output shaft speed sensor(OSS)--circuit malfunction====causes--wiring--OSS sensor--ECM/TCM
of it has just happened check the wiring and connections to the transmission for water and corrosion or replace the OSS sensor in the transmission.

I looked up the code in the Haynes Repair Manual due to having the same car this is what it says for your code-P0720 Low Output SPD sensor RPM, Above 15 MPH. The relationship between the Output Shaft Speed Sensor and vehicle speed is not within acceptable limits.

before 1996 they use onboard diagnosis system for jeep.

when you turn on key you need to count check engine light blinks.

here are codes taken from internet.

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)

There are 2 possibilities here:
1.- There may be a problem with the new speed sensor, the electrical wiring between the speed sensor and the PCM, or an internal PCM problem. To see if VSS signal is present at the PCM a scan tool capable of displaying live data is required.

2.- There is a recall action on this model year for erroneous speed sensor signals; the cure is an updated software calibration. If your truck has not yet had the updated calibration installed, you should call your local Dodge dealership with your VIN number and ask the service department to check to see if there are any open recall actions on your vehicle. If the software calibration has not been updated yet, they will perform this procedure free of charge for you. If you do not have the current software calibration in your PCM to correct the VSS issue, you need to have this done before proceeding any further with attempting to diagnose this problem

This sensor is located at the rear of the transmission.

Symptom: P-0720 LOW OUTPUT SPEED SENSOR RPM, ABOVE 15 MPH
When Monitored and Set Condition: P-0720 LOW OUTPUT SPEED SENSOR RPM, ABOVE 15 MPH

When Monitored: Continuously with the key on, engine running, and gear selector not in park or neutral.
Set Condition: This code is set if the vehicle speed (as determined from the vehicle speed sensor), is above 15 MPH, and the output shaft speed is below 60 RPM for 2.6 seconds.

POSSIBLE CAUSES DTC CODE RETURNS:
OUTPUT SPEED SENSOR DEFECTIVE
PARK/NEUTRAL SWITCH CODE PRESENT
OUTPUT SPEED SENSOR GROUND CIRCUIT OPEN
OUTPUT SPEED SENSOR GROUND CIRCUIT SHORT TO GROUND
OUTPUT SPEED SENSOR SIGNAL CIRCUIT OPEN
OUTPUT SPEED SENSOR SIGNAL CIRCUIT SHORT TO GROUND
PCM DEFECTIVE (DRB SHOWS > 60 RPM)
OUTPUT SPEED SENSOR HARNESS OBSERVABLE DEFECT
OUTPUT SPEED SENSOR WIRING HARNESS INTERMITTENT DEFECTIVE

Hope helps.

The speed sensor is malfunctioning on the transmission.I would not fix it as a result of the age of the car.Simply use a GPS for a more accurate speed

is check engine light on, if etac sees trans problem wiil put trans into limp home mode and go into 2nd gear,sometimes when trans cold may work ok,will have to get trans computer scanned to see if input and output speed sensors are ok

you will have to change out the speed sensor on the rearend it also controls the speedometer and odometer

Low output speed sensor rpm, above 15 mph. The sensor is probably bad, it screws into the left side of the transmission extension housing. It is cheap and easy to change.

I don't know how the above could have any effect on temperature. Is the vehicle full of coolant? In my opinion you have two different issues