Komatsu D85EX-15 Fault Code E-17: Complete Diagnostic Guide

What is Komatsu D85EX-15 Fault Code E-17?

Fault Code E-17 on the Komatsu D85EX-15 bulldozer indicates a transmission control system malfunction, specifically related to the transmission clutch pressure sensor circuit or transmission oil temperature sensor abnormality. This code triggers when the Electronic Control Module (ECM) detects voltage irregularities, signal dropouts, or out-of-range readings from the transmission's monitoring sensors.

The D85EX-15's hydrostatic transmission (HST) relies on precise pressure and temperature monitoring to modulate clutch engagement and maintain optimal hydraulic fluid temperatures. When E-17 appears, the ECM cannot accurately verify transmission operating conditions, which compromises shift quality, torque converter lockup, and overall drivetrain protection. For used machines, this code often surfaces due to sensor degradation or harness damage from years of vibration and heat exposure.

Common Symptoms

• Transmission warning lamp illuminated on the instrument panel (amber or red depending on severity)
• Erratic shifting behavior including harsh engagements, delayed response, or failure to shift between forward/reverse ranges
• Reduced machine power as the ECM may activate derate mode to protect the transmission from overheating or pressure loss
• Intermittent code activation that appears during specific operations (loading, grading) but clears after shutdown
• Abnormal transmission noise such as whining or grinding during clutch engagement

Potential Causes

• Transmission oil temperature sensor failure – thermal cycling degrades sensor accuracy over time
• Clutch pressure sensor malfunction – diaphragm fatigue or contamination affects pressure readings
• Wiring harness damage – vibration causes wire chafing at the transmission bellhousing or frame contact points (common on D85EX models near the left track frame)
• Corroded electrical connectors – moisture intrusion at sensor plugs creates resistance issues
• Low transmission fluid level causing actual pressure/temperature anomalies that trigger sensor alerts
• ECM software glitches or corrupted calibration files in older machines with 10,000+ operating hours

How to Troubleshoot and Fix Code E-17

Step 1: Visual Inspection and Fluid Check Begin by verifying transmission oil level using the sight glass with the machine at operating temperature. Inspect the sensor harness routing from the transmission housing to the ECM, focusing on areas where cables contact the frame or pass through grommets. Look for abraded insulation, melted wire jackets, or greenish corrosion at connector pins.

Step 2: Sensor Circuit Testing Using a digital multimeter (DMM), disconnect the transmission oil temperature sensor (typically a 2-pin connector on the right side of the transmission case). Measure resistance across sensor terminals – specification is usually 200-400 ohms at 68°F (consult your service manual). Check the clutch pressure sensor output voltage with the ignition on, engine off (should read 0.5-4.5V). Out-of-spec readings confirm sensor replacement is needed.

Step 3: Harness Continuity and ECM Diagnostics With sensors disconnected, test wiring continuity from each sensor connector back to the ECM pins (reference wiring diagrams). Check for shorts to ground or opens. Connect Komatsu KOMTRAX diagnostic software or a compatible scan tool to monitor live sensor data during operation. Compare actual transmission temperature (use infrared thermometer) against ECM-displayed values – discrepancies exceeding 15°F indicate sensor drift.

For Used Excavators: Prioritize inspecting connector seals and harness routing before ordering sensors. Used D85EX machines frequently develop connector backprobing damage from previous repairs. Clean all pins with electrical contact cleaner and apply dielectric grease during reassembly.

---

Disclaimer: This guide provides general diagnostic procedures. Always consult the official Komatsu D85EX-15 service manual and consider professional evaluation for complex transmission issues. Improper diagnosis may cause further component damage.