Volvo Excavator Operator’s Manual

Complete technical manual for the electrical system of Volvo excavators. Covers diagnostics, maintenance, testing and repair of electrical circuits, control units and sensors. The section is designed for engineers, electricians and technicians servicing crawler and wheeled excavators of the EC, EW, ECR series.

• Diagnostics of units: ECU, VECU, BCU, I-ECU, CCM
• Checking and replacing sensors: temperature, pressure, level
• CAN bus operation, resistance, communication errors
• Maintenance of starters, generators, batteries
• Checking the ground and condition of connectors
• Location and purpose of fuses and relays
• DTC codes: description, causes, elimination

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1. ⚡ Electronics problems (V-ECU, BCU, CCM)

Symptoms: errors on the display, random engine stop, function failure

Causes:

CAN bus break or connector oxidation

Control unit failures due to moisture

Power or ground fault (especially under the cab)

✅ Solution: diagnostics via Volvo Tech Tool, power and ground check, harness repair

2. 🔋 Battery discharge / alternator malfunction

Symptoms: weak start, battery does not charge

Causes:

Faulty voltage regulator

Hidden leakage current through the ignition or lighting system

The alternator fails when operating in dust and moisture

✅ Solution: check voltage and charging current, clean the alternator, replace if necessary

3. 🌡️ Engine or hydraulic system overheating

Symptoms: the lamp lights up overheating, sudden power loss

Causes:

Clogged cooling radiators

Electric fan (or clutch) does not work

Faulty temperature sensor or thermostat

✅ Solution: cleaning radiators, checking thermostat and electric circuit of fan

4. 💧 Hydraulic leaks

Symptoms: pressure loss, dirt and oil in the area of connections

Causes:

Worn seals on the rotating tower, distributor

Frayed high-pressure hoses

Stripped threads on fittings

✅ Solution: localizing the leak, replacing the damaged unit or seal

5. 🧠 Hydraulic control problems / jerks

Symptoms: booms twitch, incorrect bucket operation

Causes:

Clogged hydraulic filter

Failures in servo valve control or BCU

Problems with position sensors arrows/steering

✅ Solution: check the system pressure, diagnose the BCU, clean/replace filters

6. 🕹️ Incorrect operation of joysticks/control levers

Symptoms: control is delayed, does not obey

Causes:

Broken travel sensors in the joystick

Problem in the signal supply circuit to the hydraulic distributor

Damaged wiring at the base of the joysticks

✅ Solution: replace the joystick module, test the circuits

7. 🧯 Difficult engine starting (especially in winter)

Symptoms: the starter turns for a long time, does not start

Causes:

Worn glow plugs (if any)

Low fuel pressure, air leak

Problems with the crankshaft/camshaft position sensor

✅ Solution: measure the fuel pressure, test the ECU for errors, warm up and start from the air - temporarily

Device Comment

Hydraulic unit connectors: suffer from moisture and vibration

Harnesses under the cabin and tank: often damaged

BCU and VECU: failures from moisture or voltage surges

Pressure/temperature sensors: often fail without an error

Denso/Bosch generators: wear of brushes and bearings