Case IH 443 – Engine Controller (ECM / ENG): Decelerator or Hand Throttle (STD cab) 5 Volt Supply voltage is too low

The 5-volt reference signal provided by the engine controller to the throttle position potentiometer has dropped below the acceptable operating threshold.

• MX Magnum
• STX Steiger
• Case IH Magnum series
• Case IH MX and TG series tractors
• Case IH Puma and Steyr CVT series
• Tractors equipped with 8.3L, 9.0L, and 15L engines

1. 1

   Perform a sensor isolation test (internal short cause): Disconnect the wiring harness from the throttle potentiometer, turn the key ON, and measure voltage at the supply pin. If it returns to ~5.0V, the sensor is internally shorted.

2. 2

   Inspect wiring harness (short to ground cause): If voltage remains low with the sensor disconnected, trace the wire from the throttle connector back to ECM Pin B29. Look for chafed insulation rubbing against the cab floor or chassis.

3. 3

   Inspect connectors (corrosion/moisture cause): Check the ECM connectors and throttle pedal connectors for water intrusion, bent pins, or green corrosion.

1. 1

   Disconnect Power

   Turn off the ignition and disconnect the negative battery cable to protect the ECM.

2. 2

   Wiring Repair

   If a short to ground was found in the harness during diagnostics, splice and repair the damaged wire using weather-sealed heat shrink connectors, or replace the affected harness section.

3. 3

   Sensor Replacement

   Remove the trim panels surrounding the right-hand console (for hand throttle) or the floor mat/lower dash trim (for foot throttle). Unbolt the throttle pedal assembly or hand throttle lever bracket. Install the new potentiometer or complete pedal assembly. Reconnect the sensor wiring harness.

4. 4

   Reassembly & Clearing

   Reconnect the battery. Turn the key to the ON position and use your diagnostic tool or the tractor's instrumentation display to clear the inactive fault codes.

5. 5

   Calibration

   Depending on the specific tractor model, you may need to perform a throttle calibration procedure via the tractor's display monitor so the ECM can learn the new sensor's minimum (idle) and maximum (wide-open) voltage values.