Komatsu PC800-7 Fault Code E112: Complete Diagnostic Guide

What is Komatsu PC800-7 Fault Code E112?

Fault Code E112 on the Komatsu PC800-7 indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal coolant temperature reading detected by the Engine Control Module (ECM). This code specifically relates to the coolant temperature sensor sending irregular voltage signals outside the manufacturer's specified parameters, typically between 0.5-4.5 volts.

The coolant temperature sensor plays a critical role in the PC800-7's SAA6D170E-3 engine management system. It directly influences fuel injection timing, engine warm-up cycles, and protective shutdown protocols. When this sensor fails or provides inaccurate data, the ECM cannot properly regulate engine performance, potentially leading to overheating, poor fuel economy, or catastrophic engine damage.

Common Symptoms

When Code E112 is active, operators typically experience:

• Warning light illumination on the monitor panel, often accompanied by an audible alarm
• Engine derate mode activation, limiting power output to 70-80% of normal capacity
• Erratic temperature gauge readings or gauge stuck at minimum/maximum positions
• Difficult cold starts or extended warm-up periods due to improper fuel mapping
• White or black exhaust smoke indicating incorrect fuel-to-air ratios based on false temperature data

Potential Causes

The most common technical causes for E112 on used PC800-7 excavators include:

• Coolant temperature sensor failure due to age-related degradation or thermal cycling stress
• Wiring harness damage at known rub points near the engine block mounting brackets
• Corroded or loose connector pins at the sensor plug, especially on machines operating in wet environments
• ECM internal circuit failure (less common but possible on high-hour machines)
• Coolant contamination causing sensor element coating or failure
• Ground circuit issues affecting sensor reference voltage

How to Troubleshoot and Fix Code E112

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located on the engine block's coolant passage. Check the wiring harness for abrasion, particularly where it routes near moving components. On used excavators, examine connector pins for corrosion or bent terminals—clean with electrical contact cleaner if necessary.

Step 2: Electrical Testing Using a digital multimeter, measure sensor resistance. At 20°C (68°F), resistance should read approximately 2,000-3,000 ohms (consult service manual for exact specifications). Test harness continuity from sensor to ECM connector pins. Check for proper ground circuit integrity (less than 1 ohm resistance).

Step 3: Live Data Analysis Connect Komatsu diagnostic software (KOMTRAX Plus) or compatible scan tool. Monitor live coolant temperature readings while engine warms up. The reading should gradually increase from ambient to operating temperature (82-95°C). Erratic jumps or frozen values indicate sensor or wiring failure.

Step 4: Component Replacement If testing confirms sensor failure, replace with genuine Komatsu parts (Part #6732-81-3110 or equivalent). For used machines, always replace the sensor O-ring and apply anti-seize compound to threads. Clear codes and perform a test cycle.

Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu PC800-7 service manual and consider professional technician assistance for complex electrical diagnostics or if unfamiliar with high-voltage systems.