What is Kato HD820-R5 Fault Code E35?

Fault Code E35 on the Kato HD820-R5 excavator indicates a hydraulic pilot pressure sensor circuit malfunction or abnormal signal voltage. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects voltage readings outside the normal operating range (typically 0.5-4.5V) from the pilot pressure sensor, which monitors hydraulic control pressure in the joystick and pedal circuits.

This sensor is critical for the HD820-R5's proportional hydraulic control system. It allows the ECM to interpret operator input intensity and modulate main control valve response accordingly. When E35 appears, the machine may default to limp mode or reduce hydraulic response sensitivity, directly impacting productivity and operational precision on job sites.

Common Symptoms

When Code E35 is active on your Kato HD820-R5, operators typically experience:

• Warning light illumination on the instrument cluster, often accompanied by an audible alarm
• Reduced hydraulic responsiveness or erratic boom/arm/bucket movements despite normal joystick input
• Inconsistent swing speed or complete loss of fine control during precision work
• Intermittent code appearance that clears and returns, especially during cold starts or after extended operation
• ECM derate mode limiting engine RPM to protect hydraulic systems from uncontrolled movements

Potential Causes

The most common technical failures triggering E35 on used HD820-R5 excavators include:

• Pilot pressure sensor failure due to internal diaphragm deterioration or contaminated hydraulic fluid exposure
• Wiring harness damage at known rub points near the center joint swivel or along the boom base where cables flex repeatedly
• Connector corrosion at the sensor's 3-pin Deutsch connector, particularly common in machines operating in coastal or high-humidity environments
• ECM voltage supply issues providing incorrect reference voltage (typically should be 5V ±0.25V)
• Hydraulic fluid contamination causing sensor port blockage or pressure spike damage
• Ground circuit faults creating voltage offset in sensor readings

How to Troubleshoot and Fix Code E35

Step 1: Visual Inspection and Connector Check Begin by locating the pilot pressure sensor on the main control valve block (right side of the operator platform). Disconnect the sensor harness and inspect the connector pins for corrosion, bent terminals, or hydraulic fluid intrusion. On used excavators, this connector frequently shows green corrosion due to moisture ingress. Clean with electrical contact cleaner and apply dielectric grease.

Step 2: Sensor Circuit Testing Using a digital multimeter (DMM), backprobe the sensor connector with the ignition ON, engine OFF. Verify 5V reference voltage on the signal wire (typically the red wire). Check ground continuity to chassis (should be <0.5Ω resistance). With the sensor connected, measure output voltage while manually operating a joystick—readings should smoothly vary between 0.8-4.2V. Static readings or sudden jumps indicate sensor failure.

Step 3: Harness and ECM Verification Inspect the wiring harness from sensor to ECM, focusing on the center joint area where Kato HD820 series machines commonly experience cable abrasion against the swing bearing housing. Check for shorts to ground or power using resistance measurements (circuit should show >10kΩ to ground with sensor disconnected). If wiring passes inspection but code persists, use Kato diagnostic software (KES) to monitor live sensor data and verify the ECM isn't logging multiple pressure-related codes, which could indicate ECM internal faults.

Step 4: Component Replacement Protocol For used machinery, replace the sensor with a genuine Kato part (PN: 2448U410F2) rather than aftermarket alternatives, as voltage curve calibration is model-specific. After installation, clear codes, perform a pilot pressure calibration procedure through the diagnostic software, and conduct a full hydraulic function test under load.

Disclaimer: This guide provides general troubleshooting information for experienced technicians. Always consult the official Kato HD820-R5 service manual and follow proper lockout/tagout procedures. If unfamiliar with hydraulic systems or electrical diagnostics, seek assistance from a certified Kato dealer or qualified heavy equipment technician.