Case IH 147 – Engine Control Module (ECM): Frequency Throttle Signal is shorted high

The Engine Control Module (ECM) has detected a frequency of less than 100 Hz at the frequency throttle input circuit. This condition points to an electrical fault (a short to a high voltage source or an open circuit) in the accelerator pedal position sensor, the hand throttle potentiometer, or the wiring harness connecting them to the ECM.

• MX Magnum
• STX Steiger
• Steiger
• STX
• Puma
• CVX

1. 1

   Inspect the Sensor Connectors: Disconnect the accelerator pedal position sensor and/or hand throttle potentiometer. Check the pins for corrosion, moisture, or bent terminals.

2. 2

   Test the Wiring Harness: Using a multimeter, check the frequency throttle signal circuit between the throttle sensor connector and the ECM. Look for a short to a high voltage source (e.g., battery voltage) or an open circuit.

3. 3

   Check the Frequency Output: Verify if the frequency at the ECM input drops below the 100 Hz threshold when the throttle is actuated.

4. 4

   Check for Related Codes: Look for accompanying codes (like 148 - Frequency Throttle Signal shorted low, or codes 131/132/133/134 related to remote accelerator position sensors) which can help pinpoint if the issue is in the hand throttle vs. the foot pedal.

1. 1

   Disconnect Power

   Turn off the key switch and disconnect the battery ground to prevent electrical spikes.

2. 2

   Access the Throttle Sensor

   Locate the faulty throttle input device (either the foot accelerator pedal assembly or the right-hand console hand throttle potentiometer, depending on which is throwing the fault).

3. 3

   Repair Wiring

   If the diagnostic checks revealed a short to a high voltage source in the harness, locate the chafed wire or melted insulation and repair the harness.

4. 4

   Replace the Sensor

   If the wiring tests good, the internal potentiometer/sensor has failed. Remove the mounting screws securing the throttle position sensor or pedal assembly and install the replacement unit.

5. 5

   Reassemble and Calibrate

   Reconnect the sensor harness and battery. Some models may require a throttle calibration procedure via the tractor's instrumentation or a dealer service tool so the ECM can relearn the 0-100% throttle sweep.

6. 6

   Clear Codes

   Clear the inactive fault code 147 from the ECM and test-drive the machine to verify normal throttle response.