Sumitomo SH80-6B Fault Code P1568-1: Technical Guide

What is Sumitomo SH80-6B Fault Code P1568-1?

Fault Code P1568-1 indicates an abnormal signal detected in the engine control system's throttle position sensor (TPS) circuit, specifically a voltage deviation or intermittent connection issue. This diagnostic trouble code (DTC) is generated when the Electronic Control Module (ECM) detects that the throttle position sensor is sending voltage readings outside the manufacturer's specified range or experiencing signal interruptions.

For the Sumitomo SH80-6B excavator, this code directly affects the diesel engine's ability to properly regulate fuel delivery and engine speed. The TPS is critical for coordinating engine RPM with hydraulic pump demands, meaning this fault can significantly impact both machine performance and fuel efficiency. In used excavators, this code often appears due to age-related sensor degradation or wiring harness wear.

Common Symptoms

When Code P1568-1 is active, operators typically experience:

• Engine warning light illuminated on the instrument cluster with possible derate mode activation
• Erratic engine RPM or throttle response, particularly during load changes or swing operations
• Intermittent loss of power when operating hydraulic functions under heavy demand
• Rough idle or engine hunting (RPM fluctuation) at low throttle positions
• Reduced hydraulic performance due to inconsistent engine speed regulation

Potential Causes

The most common technical causes for P1568-1 on used SH80-6B excavators include:

• Worn or contaminated throttle position sensor with internal resistance changes due to age
• Damaged wiring harness between the TPS and ECM, especially at known rub points near the engine firewall and along the chassis frame
• Corroded or loose connector pins at the TPS connector or ECM interface
• Poor ground connection affecting sensor reference voltage stability
• ECM software calibration issues or internal ECM failure (less common)
• Voltage supply problems from the machine's electrical system affecting sensor power

How to Troubleshoot and Fix Code P1568-1

Step 1: Initial Inspection Begin with a thorough visual inspection of the throttle position sensor mounted on the engine's fuel injection pump or governor assembly. Check for physical damage, oil contamination, or loose mounting. On used excavators, verify all connector pins for corrosion or backing out—a common issue on machines with 5,000+ operating hours.

Step 2: Electrical Testing Using a digital multimeter, measure the TPS output voltage with ignition ON, engine OFF. Reference voltage should typically be 5V at the sensor. Check signal wire voltage while slowly moving the throttle from idle to full—readings should smoothly transition from approximately 0.5V to 4.5V without jumps or dropouts. Test harness continuity between the sensor and ECM, paying special attention to areas where the harness runs along vibration-prone mounting points.

Step 3: Advanced Diagnostics Connect manufacturer-specific diagnostic software (or compatible heavy equipment scan tool) to monitor live TPS data. Observe for signal dropouts or erratic voltage spikes during wiggle testing of connectors and harness sections. Inspect the ground circuit resistance—it should read less than 1 ohm to chassis ground.

Step 4: Component Replacement If testing confirms sensor failure, replace the throttle position sensor with OEM or high-quality aftermarket parts. After replacement, clear fault codes and perform a calibration procedure using diagnostic software. For harness issues, repair damaged sections with proper gauge wire and heat-shrink connections, ensuring routing avoids sharp edges and excessive heat zones.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Sumitomo service manual for your specific machine serial number and consider professional diagnostic assistance for complex electrical issues or ECM programming requirements.