Sumitomo SH80-6B Fault Code P1644-2: Technical Guide

What is Sumitomo SH80-6B Fault Code P1644-2?

Fault Code P1644-2 on the Sumitomo SH80-6B excavator indicates a malfunction in the Engine Control Module (ECM) communication circuit, specifically a data link error between the engine ECM and the machine's main controller.

This code is triggered when the Controller Area Network (CAN) bus detects intermittent or complete loss of communication between control modules. The SH80-6B relies on continuous data exchange between the engine ECM and hydraulic controller to optimize fuel delivery, emissions control, and hydraulic performance. When this communication fails, the machine cannot properly coordinate engine power with hydraulic demand, potentially causing operational inefficiencies and triggering protective derate modes.

This fault is particularly critical for the SH80-6B because this model uses integrated electronic control to balance engine load with hydraulic system pressure, ensuring fuel economy and preventing component damage during heavy digging operations.

Common Symptoms

• Warning lights: Check Engine light illuminated on the instrument panel; possible Master Caution light activation
• Power derate: Engine automatically limits RPM to 1500-1800 range, reducing digging force and travel speed
• Erratic hydraulic response: Sluggish boom/arm movements or inconsistent swing speed due to loss of load-sensing data
• Intermittent starting issues: ECM may fail to receive proper ignition authorization from main controller
• Error message display: Digital monitor shows communication error or system fault notifications

Potential Causes

Wiring harness damage is the most common culprit in used SH80-6B machines, particularly where the main harness passes near the swing bearing or along the boom base—known friction points for this model.

Corroded or loose CAN bus connectors, especially the 8-pin Deutsch connector behind the operator's seat that links engine and chassis harnesses.

ECM or main controller failure, though less common; voltage spikes from jump-starting or electrical system issues can damage communication circuits.

Poor ground connections at the battery negative terminal or chassis ground points, causing voltage reference errors.

Aftermarket component interference, such as non-OEM radios or tracking devices improperly wired into the electrical system.

How to Troubleshoot and Fix Code P1644-2

Step 1: Visual Inspection of Harnesses Begin by inspecting the main wiring harness from the engine compartment to the cab, focusing on areas where cables contact metal edges or moving components. On used excavators, check for harness wear near the swing bearing race and along the right-side frame rail. Look for abraded insulation, pinched wires, or zip-tie damage.

Step 2: Test CAN Bus Connectivity Using a digital multimeter, measure resistance between CAN-High and CAN-Low pins at the ECM connector (consult service manual for pin locations—typically pins 23 and 24). You should read approximately 60 ohms with ignition off. Check for 120-ohm terminating resistors at each end of the CAN network. Remove and inspect all CAN bus connectors for green corrosion or bent pins.

Step 3: Verify Power and Ground Circuits Measure battery voltage at ECM power supply pins with ignition on—should read 24V±2V. Check ground circuit resistance from ECM ground pin to battery negative; reading should be below 0.5 ohms. Clean all ground connection points with wire brush and apply dielectric grease.

Step 4: Software Diagnostics Connect Sumitomo diagnostic software (or compatible tool like Jaltest) to retrieve freeze-frame data showing when communication failed. Monitor live CAN bus traffic to identify if fault is intermittent. Clear codes and perform operational test under load.

For used excavators, always replace damaged harness sections rather than splicing, as improper repairs create future failure points. Check connector seals for water intrusion, common in older machines stored outdoors.

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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.