What is Sumitomo SH300-6 Fault Code 87?

Fault Code 87 on the Sumitomo SH300-6 excavator indicates a malfunction in the travel motor system, specifically related to abnormal electrical signals from the travel motor speed sensors or their associated circuits. This diagnostic trouble code (DTC) is generated by the machine's Electronic Control Unit (ECU) when it detects inconsistent or out-of-range data from the sensors that monitor track motor rotation speed.

This code is critical for the SH300-6 because the travel motor speed sensors provide essential feedback to the hydraulic control system, enabling precise travel speed modulation and preventing damage from over-speed conditions. When Code 87 is active, the machine may enter a protective derate mode to prevent potential drivetrain damage, significantly impacting jobsite productivity.

Common Symptoms

When Fault Code 87 is active on your Sumitomo SH300-6, operators typically experience:

• Warning light illumination on the main instrument panel, often accompanied by audible alarm
• Reduced travel speed or uneven track movement (one track may respond differently than the other)
• Intermittent loss of travel function, where the machine stops responding to travel controls momentarily
• Erratic track motor behavior, including jerky movements or unexpected speed variations
• ECU fault code storage visible through diagnostic software, even if symptoms are intermittent

Potential Causes

The most common technical causes for Code 87 on used SH300-6 excavators include:

• Failed or contaminated travel motor speed sensors due to seal degradation allowing hydraulic oil or debris infiltration
• Damaged sensor wiring harness caused by rubbing against the track frame or swing bearing—a known wear point on older SH300 models
• Corroded or loose electrical connectors at the sensor interface or ECU connection points
• Air gap issues between the speed sensor and the target gear, often caused by mounting bracket wear or sensor positioning shift
• ECU internal faults or corrupted programming, though less common than sensor-circuit issues
• Hydraulic contamination affecting sensor magnetics, particularly in machines with poor maintenance history

How to Troubleshoot and Fix Code 87

Step 1: Initial Diagnostic Scan Connect a compatible diagnostic tool (Sumitomo diagnostic software or multi-brand scanner like Jaltest) to retrieve active and stored codes. Document freeze frame data showing sensor voltage readings and operating conditions when the fault occurred.

Step 2: Visual Inspection Physically inspect both travel motor speed sensors and their wiring harnesses. On used excavators, check for harness abrasion where wires route near moving components, particularly around the swing bearing area. Examine connector pins for corrosion, bent terminals, or moisture intrusion—common issues on machines exceeding 5,000 operating hours.

Step 3: Sensor Testing Using a digital multimeter, measure sensor resistance (typically 800-1,200 ohms for most inductive speed sensors, but verify against Sumitomo specifications). Check supply voltage at the sensor connector (should be 8-12V DC). Verify proper air gap between sensor tip and reluctor ring (usually 0.5-1.5mm).

Step 4: Circuit Continuity Check Test wiring continuity from each sensor back to the ECU connector. Check for short circuits to ground or voltage supply. Pay special attention to harness sections that flex during swing operations.

Step 5: Component Replacement If sensors test faulty, replace with OEM or high-quality aftermarket parts. When installing, apply dielectric grease to connectors and ensure proper harness routing with adequate strain relief. Clear codes and perform operational testing under load.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Sumitomo service manual for your specific machine serial number. Complex electrical diagnostics should be performed by certified technicians with proper equipment to avoid injury or further machine damage.