John Deere 91.03 – ECU, CAB, EPC, CCU, OIC: Foot Throttle Sensor Circuit Voltage Problem / Accelerator Pedal Signal Voltage High

The control unit measures a voltage in excess of 4.7 volts at the signal input of the accelerator pedal potentiometer (sensor B79 or B21). This overvoltage condition indicates that the primary analog throttle signal is out of range high, which usually means the circuit is shorted to a supply lead, is open, or the sensor itself has failed internally.

• 5065M
• 5075M
• 5085M
• 5100M
• 5100MH
• 5100ML
• 5115ML
• 5095M
• 5095MH
• 5105M
• 5015ML
• 5E Series
• 5045E
• 5055E
• 5065E
• 6M/6R Series
• 6110M
• 6120M
• 6130R
• 6155M
• 7000/8000 Series
• 8230T
• 8330T
• 8430T
• 6020-6920S
• 444J
• 544J
• 624J
• CT332
• 331G
• 333G
• 4930
• 460E

1. 1

   Test Potentiometer Functionality (Voltage Check): Check the signal voltage directly from the throttle position sensor. A healthy sensor should read between 0.5 volts and 4.5 volts (around 0.65V for low idle and 4.35V for fast idle). If the voltage exceeds 4.7V, the code is triggered.

2. 2

   Inspect Wiring for Shorts: Check the wiring harness associated with the accelerator pedal potentiometer for any signs of short circuits to the power supply lead. Look for damaged insulation, rubbed-through wire loom, or exposed wires.

3. 3

   Verify Connections: Inspect all connectors and terminals in the circuit (both at the pedal and at the control module). Look for loose, backed-out, or corroded pins.

4. 4

   Check for Open Circuits: Use a multimeter to test for continuity between the sensor connector and the module to ensure there are no broken wires.

1. 1

   Disconnect Power

   Disconnect the machine's battery before starting work to prevent electrical surges or accidental shorts while handling electronic components.

2. 2

   Locate the Sensor

   Locate the foot throttle sensor/accelerator pedal potentiometer. On most tractors and loaders, it is mounted directly under the operator platform attached to the pedal linkage.

3. 3

   Remove the Old Sensor

   Unplug the electrical connector from the sensor. Unbolt the sensor from the pedal assembly bracket.

4. 4

   Install the New Sensor

   Mount the new potentiometer to the pedal assembly. This is typically a direct replacement that requires no mechanical modifications.

5. 5

   Reconnect

   Plug the wiring harness back into the sensor and reconnect the battery.

6. 6

   Reset and Relearn

   Clear the stored 000091.03 fault code using a diagnostic tool or the machine's display menu. Turn the key on and test the accelerator pedal response. Note: Some machines may require a few minutes of operation to relearn the new sensor's exact voltage sweep.