Sumitomo SH80-6B Fault Code U1167-8: Complete Diagnostic Guide

What is Sumitomo SH80-6B Fault Code U1167-8?

Fault Code U1167-8 indicates a CAN communication error between the Engine Control Module (ECM) and the Monitor Control Unit (MCU), specifically reporting an "Invalid or Missing Message" with a moderately severe failure mode indicator (FMI 8). This U-code classification means the issue involves network communication between control modules rather than a single component failure.

On the Sumitomo SH80-6B excavator, this code affects the CAN bus network, which allows critical systems to share operational data. The ECM (engine controller) and MCU (monitor/display controller) must maintain constant communication for proper machine performance monitoring, diagnostics, and operator alerts. When this communication link degrades or fails, the machine cannot properly coordinate engine operations with display functions, potentially limiting performance or preventing accurate fault reporting.

This is particularly critical on the SH80-6B because the integrated monitoring system relies on real-time data exchange to manage fuel efficiency, emissions compliance, and hydraulic system coordination.

Common Symptoms

When U1167-8 is active, operators typically experience:

• Dashboard warning lights illuminated (check engine or system malfunction indicators)
• Inaccurate or frozen gauge readings on the instrument cluster (RPM, temperature, fuel level)
• Intermittent loss of display functions or complete monitor blackout
• Engine derate or limp mode in severe cases, limiting machine to reduced RPM
• Multiple secondary fault codes appearing simultaneously due to communication loss

Potential Causes

The most common technical reasons for U1167-8 on used SH80-6B excavators include:

• Corroded or damaged CAN bus connectors at the ECM or MCU (common in machines with 5,000+ hours)
• Chafed or pinched wiring harness along the chassis rail near the counterweight pivot point (known wear location)
• Failed CAN bus terminating resistor (120-ohm resistor failure disrupts entire network)
• ECM or MCU internal communication circuit failure due to voltage spikes or water intrusion
• Loose or oxidized ground connections at the battery or frame ground points
• Aftermarket component interference (non-OEM radios or accessories causing electrical noise)

How to Troubleshoot and Fix Code U1167-8

Step 1: Visual Harness Inspection Physically inspect the main wiring harness from the ECM (typically located near the engine) to the MCU (behind the operator cab). On used excavators, focus on areas where harnesses contact metal frames, especially near the swing bearing and along the right-side chassis rail. Look for abraded insulation, pinched wires, or moisture in connector boots.

Step 2: Test CAN Bus Integrity Using a digital multimeter, measure resistance between CAN-High and CAN-Low terminals at the ECM connector with the key off and all modules disconnected. You should read approximately 60 ohms (two 120-ohm terminating resistors in parallel). A reading of 120 ohms indicates one terminating resistor has failed; infinite resistance means an open circuit in the bus wiring.

Step 3: Check Power and Ground Circuits Verify the MCU receives proper battery voltage (12-14V) at its power supply pin with the key on. Test the ground circuit continuity (should be less than 0.5 ohms to battery negative). Corroded grounds are extremely common on excavators operating in wet or marine environments.

Step 4: Connector Cleaning and Reseating Disconnect both the ECM and MCU connectors, spray with electrical contact cleaner, and inspect for bent pins or green corrosion. Apply dielectric grease before reconnecting. This simple step resolves approximately 40% of U-codes on used machinery.

Step 5: Advanced Diagnostics If basic checks pass, use Sumitomo diagnostic software or a compatible J1939 CAN scanner to monitor live CAN bus traffic. Look for message transmission failures or irregular data packet intervals. Replace the ECM or MCU only after confirming the harness and terminating resistors are functional.

Disclaimer: While this guide provides comprehensive troubleshooting steps, CAN bus diagnostics can be complex. If you're uncomfortable working with electronic control systems or lack proper diagnostic tools, consult a certified Sumitomo technician or qualified heavy equipment electrician to prevent further damage to control modules.