What is Volvo EC950E L Fault Code P117800?

Fault Code P117800 indicates a malfunction in the Engine Control Module (ECM) communication with the hydraulic system's proportional pressure control solenoid or valve driver circuit. This diagnostic trouble code (DTC) specifically signals that the ECM has detected an abnormal voltage, current draw, or response time from the hydraulic pressure control system's electronic actuator.

In the Volvo EC950E L excavator, this code directly affects the machine's ability to regulate hydraulic system pressure through electronic control. The ECM continuously monitors feedback signals from pressure control solenoids to ensure optimal hydraulic performance. When communication fails or signal values fall outside predetermined parameters (typically 0.5-4.5 volts), the system logs P117800. This is critical because the EC950E L relies on precise electronic-over-hydraulic control for efficient operation of its large-capacity hydraulic pumps and actuators. Compromised pressure regulation can lead to reduced lifting capacity, sluggish response, and potential damage to expensive hydraulic components.

Common Symptoms

• Hydraulic system derate with noticeably reduced digging force and slower cycle times
• Amber warning light illuminated on the instrument cluster with possible pressure-related fault messages
• Erratic boom or bucket movement with inconsistent speed or jerky operation during combined functions
• Engine power limitation as the ECM enters protective mode to prevent hydraulic system damage
• Intermittent loss of auxiliary hydraulic functions or attachment controls

Potential Causes

The most frequent causes of P117800 in used EC950E L excavators include:

• Damaged wiring harness near the main hydraulic pump area where cables experience vibration and heat exposure
• Failed proportional pressure control solenoid due to internal coil breakdown or contaminated hydraulic oil causing valve sticking
• Corroded electrical connectors at the solenoid interface, common in machines operating in wet or marine environments
• ECM internal driver circuit failure from voltage spikes or age-related component degradation
• Hydraulic oil contamination affecting solenoid valve operation and creating electrical resistance issues
• Worn harness grommets at bulkhead pass-throughs allowing moisture intrusion specific to the EC950E frame design

How to Troubleshoot and Fix Code P117800

Step 1: Visual Inspection Begin by thoroughly inspecting the wiring harness running from the ECM to the main hydraulic pump assembly. On used excavators, check for harness wear at mounting brackets, particularly where cables contact the engine block or hydraulic tank. Look for chafed insulation, oil-soaked wires, or corroded connectors. The EC950E L has known rub points near the left-side pump mounting—inspect this area carefully.

Step 2: Electrical Testing Using a digital multimeter, disconnect the proportional pressure control solenoid connector and measure coil resistance (typically 8-15 ohms for Volvo solenoids—verify with service manual). Check for voltage supply at the harness side with ignition on (should read battery voltage). Measure ground circuit continuity to ensure less than 0.5 ohms resistance to chassis ground.

Step 3: Solenoid and ECM Verification Connect Volvo VCADS Pro diagnostic software to monitor real-time solenoid command values versus actual response. Command the solenoid through various percentages and observe response time. If electrical tests pass but response is sluggish, remove and inspect the solenoid valve for contamination or mechanical binding. For used machines, replace hydraulic oil filter and sample oil for contamination analysis before condemning electrical components.

Step 4: Harness Repair or Replacement If testing reveals intermittent connections or resistance issues, repair damaged sections using heat-shrink solder connectors rated for hydraulic system temperatures. Replace entire harness sections showing oil saturation, as petroleum degrades insulation over time.

Disclaimer: This guide provides general troubleshooting procedures. Always consult the official Volvo service manual for your specific machine serial number. Complex electrical and hydraulic diagnostics should be performed by certified technicians with proper diagnostic equipment to prevent injury or further equipment damage.