Case IH 91-02 - VCM – VCM: Throttle Position Sensor (TPS) or Accelerator Pedal (AP) sensor erratic, intermittent, or incorrect data signal

There is a disagreement between the analog foot pedal position sensor and the digital idle validation switch (IVS). If the pedal position sensor indicates the pedal is pressed, but the idle validation switch indicates the pedal is still in the closed/idle position (or vice versa), the system registers a disagreement and logs the 91-02 fault. When this code is active, the engine speed typically defaults to low idle or a predetermined safe speed.

• MAGNUM AFS Connect
• Patriot Sprayers 3230
• Patriot Sprayers 3330
• Patriot Sprayers 4420
• Patriot Sprayers 4430
• Patriot Sprayers SPX series
• Axial-Flow Combines 2366
• Axial-Flow Combines 2377
• Axial-Flow Combines 2388
• Axial-Flow Combines 2577
• Maxxum series (100-140)
• Steiger
• Magnum
• MX series
• Cotton Express Pickers 420
• Cotton Express Pickers CPX420

1. 1

   Inspect the wiring harness and connectors between the accelerator pedal assembly and the VCM/ECM for damage, corrosion, moisture, or loose pins.

2. 2

   Check for an open circuit (resistance greater than 40 kΩ) or a short circuit to ground in the pedal harness.

3. 3

   Perform a sensor sweep test using a multimeter or electronic service tool to monitor the Accelerator Pedal sensor input voltage. Ensure the voltage sweeps smoothly as the pedal is depressed without dropping out or spiking.

4. 4

   Test the Idle Validation Switch (IVS) circuit to ensure it properly transitions between its open and closed states exactly when the pedal leaves the low idle position.

1. 1

   Preparation

   Turn off the ignition, set the parking brake, and disconnect the battery power supply to prevent electrical shorts.

2. 2

   Access the Pedal

   Locate the accelerator pedal assembly inside the cab.

3. 3

   Disconnect Harness

   Carefully unplug the wiring harness connector from the pedal assembly.

4. 4

   Inspect and Clean

   Inspect the connector pins on both the harness and the pedal. If poor tension or corrosion is found, clean the pins or replace the terminal ends.

5. 5

   Replace Component

   If the wiring is intact but the sensor/switch failed the diagnostic tests, the entire accelerator pedal assembly (or the attached throttle position potentiometer) must be replaced, as the TPS and IVS are typically integrated into a single non-serviceable unit. Unbolt the old pedal assembly and mount the new one.

6. 6

   Reassembly

   Reconnect the wiring harness and reconnect the battery.

7. 7

   Calibration and Clearing

   Connect an electronic service tool to the machine's diagnostic port. Clear the logged 91-02 fault code and verify that the VCM is reading the new idle validation and throttle position signals correctly.