CAT 246D Accelerator Pedal Failure and Code Diagnosis

[MikePhua]

The CAT 246D and Its Electronic Control System
The Caterpillar 246D skid steer loader, part of CAT’s D-series launched in the mid-2010s, is a compact yet powerful machine designed for grading, lifting, and material handling. With a 74-horsepower turbocharged engine and electronically controlled hydrostatic drive, the 246D integrates advanced diagnostics, joystick control, and pedal-based throttle modulation. Caterpillar Inc., founded in 1925, has sold tens of thousands of D-series loaders globally, with the 246D becoming a staple in rental fleets and contractor yards.
Unlike earlier mechanical throttle systems, the 246D uses an electronic accelerator pedal connected to the machine’s ECM (Electronic Control Module). This setup allows for smoother throttle response, integration with drive-by-wire systems, and compatibility with emissions control logic. However, when the pedal fails or communication is lost, the machine may default to idle, triggering fault codes and disabling operator control.
Terminology Annotation

• ECM (Electronic Control Module): The onboard computer that manages engine, transmission, and throttle functions.
  
• Throttle Position Sensor (TPS): A sensor embedded in the pedal that reports pedal angle to the ECM.
  
• CAN Bus: A communication protocol used to link electronic components in heavy equipment.
  
• Fault Code: A diagnostic alert generated when a system component fails or behaves abnormally.
  

Symptoms of Pedal Failure
Operators have reported that the accelerator pedal becomes unresponsive, leaving the machine stuck at idle regardless of pedal input. In some cases, the machine still moves via joystick control, but engine RPM remains fixed. This behavior is often accompanied by fault codes displayed on the monitor, such as:

• Code 2687-8: Throttle position sensor abnormal signal
  
• Code 2687-5: Throttle signal out of range
  
• Code 2687-3: Throttle signal voltage low
  

These codes indicate that the ECM is receiving either no signal or an implausible signal from the pedal’s TPS. In one Michigan snow removal fleet, a 246D failed to throttle up during a storm event, forcing the operator to complete the job at idle speed. The issue was traced to a corroded pedal connector.
Initial Diagnostic Steps
Begin with a visual inspection:

• Check the pedal harness for damage, corrosion, or disconnection
  
• Inspect the connector pins for bent terminals or moisture intrusion
  
• Verify that the pedal moves freely and returns to neutral without sticking
  

Next, perform an electrical test:

• Use a multimeter to measure voltage at the TPS connector
  
• Expected values: 0.5V at idle position, up to 4.5V at full depression
  
• If voltage is absent or erratic, the sensor or harness may be compromised
  

If available, connect CAT ET (Electronic Technician) software to read live pedal data and confirm signal integrity. This tool can also clear fault codes and verify ECM response.
Common Failure Points

• Pedal Sensor: Internal wear or contamination can cause signal dropout
  
• Connector Corrosion: Moisture ingress near the floor pan is common in wet environments
  
• Harness Damage: Vibration and foot traffic can fray wires or loosen terminals
  
• ECM Fault: Rare, but possible if voltage regulation or input filtering fails
  

In one Texas landscaping crew, a 246D pedal failed after repeated pressure washing. Water had entered the connector housing, oxidizing the terminals. After cleaning and sealing the connector with dielectric grease, the pedal resumed normal function.
Repair Strategy and Recommendations
If diagnostics confirm pedal failure:

• Replace the pedal assembly with an OEM unit
  
• Clean and inspect the connector before installation
  
• Route the harness to avoid pinch points and abrasion
  
• Use dielectric grease to seal terminals against moisture
  

If the fault persists after replacement:

• Check ECM input voltage and ground reference
  
• Inspect CAN bus communication for latency or dropout
  
• Update ECM firmware if available to improve fault tolerance
  

Always clear fault codes after repair and verify pedal response under load. Test in both drive and idle modes to confirm full throttle range.
Preventive Maintenance Tips

• Avoid direct water spray on pedal and floor harness
  
• Inspect connectors quarterly for corrosion
  
• Use floor mats to reduce vibration and impact
  
• Monitor fault codes during routine service intervals
  
• Train operators to report throttle anomalies early
  

In one municipal fleet, implementing a pedal inspection protocol reduced throttle-related downtime by 80% over two years.
Final Thoughts
The CAT 246D’s electronic pedal system offers precision and integration—but it also introduces vulnerability to moisture, wear, and signal loss. When the pedal fails, the machine loses its voice. With methodical diagnostics and careful repair, throttle control can be restored, keeping the loader responsive and productive.
In the world of compact machines, even the smallest sensor matters. And when the pedal speaks clearly, the job moves forward.