The overspeed sensor is a safety feature that helps prevent the vehicle from exceeding a certain speed. It does this by monitoring the speed of the transmission input shaft and sending a signal to the engine control module (ECM) if it detects that the shaft is spinning too fast. The ECM then cuts power to the engine, preventing it from accelerating any further.
Symptoms of a faulty overspeed sensor
A faulty overspeed sensor can cause a number of problems, including:
- The engine may stall or shudder at high speeds.
- The check engine light may come on.
- The vehicle may go into limp mode, which limits the engine speed and power.
How to diagnose a faulty overspeed sensor
To diagnose a faulty overspeed sensor, you will need to:
- Check the engine for codes. A faulty overspeed sensor will typically set a code P0500 or P0501.
- Inspect the overspeed sensor. Look for any damage to the sensor or the wiring harness.
- Test the overspeed sensor. You can do this using a multimeter to measure the resistance of the sensor. The sensor's resistance should be within a certain range, which is specified in the repair manual for your vehicle.
How to replace an overspeed sensor
If the overspeed sensor is faulty, you will need to replace it. To do this, you will need to:
- Disconnect the negative battery terminal.
- Remove the air cleaner housing.
- Locate the overspeed sensor on the transmission case.
- Disconnect the wiring harness from the sensor.
- Remove the bolt that holds the sensor in place.
- Remove the sensor from the transmission case.
- Install a new sensor in the reverse order of removal.
- Connect the negative battery terminal.
- Start the engine and verify that the check engine light is off.
Additional information
The actual procedure of changing the OSS or Output Speed Sensor may differ depending on the 2WD or 4WD version of a 1997 Jeep Grand Loredo. A 2WD has the sensor on top of the transfer case or just below the transmission. A 4WD would have the sensor attached to the front differential with a wiring harness clipped into the sensor body (3 wire black connector).
