In last week’s blog article, we looked at the most common truck and trailer diagnostic issues and highlighted the most effective ways to fix them. So, it’s only right that we provide similar insight into resolving the most frequent off-highway vehicle diagnostic issues.
It is clear that construction sites demand maximum uptime from heavy equipment. Whether it’s a Caterpillar excavator, JCB telehandler, Liebherr loader, Doosan digger, BOMAG roller, or Kobelco crane, downtime costs money and productivity. In addition to this, diagnosing faults in off-highway machinery can be challenging, especially with the complexity of today’s electronically controlled engines, hydraulics, and emissions systems.
Fortunately, with Jaltest Diagnostics, workshops and operators can quickly identify, troubleshoot, and resolve issues across all major off-highway manufacturers—keeping fleets running and projects on schedule.
Here are the five most common diagnostic issues in construction machinery, with causes, solutions, and tips to fix them faster.
Hydraulic System Problems
The Issue:
Hydraulic failures are among the most common in excavators, loaders, and cranes. Symptoms include sluggish movement, overheating oil, or uneven lifting.
Causes:
- Contaminated or low hydraulic fluid.
- Blocked filters or leaking hoses.
- Malfunctioning pumps, valves, or electronic controllers.
Solution:
- Check fluid levels and replace hydraulic oil/filters if necessary.
- Use Jaltest to monitor real-time hydraulic pressure and valve signals.
- Run actuator tests to confirm solenoid and valve functionality.
Tip to Fix Faster: Jaltest allows technicians to access OEM-level parameters and live sensor data, making it easier to spot whether the fault lies in the hydraulics or the electronic controls.
Emissions System & Aftertreatment Faults (DPF, SCR, EGR)
The Issue:
Off-highway vehicles must meet stringent emissions standards. Diesel Particulate Filters (DPF), Selective Catalytic Reduction (SCR/AdBlue), and EGR valves are frequent sources of downtime.
Causes:
- Short duty cycles preventing full regeneration.
- Poor quality fuel or AdBlue fluid.
- Faulty differential pressure or temperature sensors.
Solution:
- Connect Jaltest to perform a forced regeneration of the DPF.
- Run system checks on NOx sensors, dosing modules, and EGR valves.
- Replace defective sensors or dosing units where necessary.
Tip to Fix Faster: Jaltest’s guided diagnostics provide step-by-step regeneration procedures, helping avoid unnecessary filter removal and costly downtime.
Electrical & Communication Errors (CAN Bus Failures)
The Issue:
Modern machines from Caterpillar, JCB, Liebherr, and others rely on electronic control networks. A single CAN bus error can disable multiple systems, from hydraulics to transmission.
Causes:
Damaged wiring harnesses.
Water ingress or corroded connectors.
Faulty ECU disrupting communication.
Solution:
Run a full machine scan with Jaltest to identify which module is offline.
Inspect wiring looms and connectors.
Repair or replace damaged cables/ECUs.
Tip to Fix Faster: Jaltest generates a system topology map, showing the status of every ECU in the network, saving hours of fault tracing.
Transmission & Drivetrain Issues
The Issue:
Operators often report hard gear shifts, slipping, or loss of drive in loaders, dump trucks, and graders.
Causes:
- Low or degraded transmission oil.
- Clutch pack wear.
- Faulty sensors or solenoids in the transmission control unit.
Solution:
- Inspect oil levels and condition.
- Use Jaltest to check transmission error codes and run calibration routines.
- Test solenoids and pressure sensors using Jaltest’s actuator tests.
Tip to Fix Faster: Jaltest can perform clutch calibrations and adaptations, ensuring smoother gear shifts after repairs and reducing callbacks.
Engine Performance Problems (Loss of Power, Excessive Fuel Use)
The Issue:
From excavators struggling to dig to loaders burning too much fuel, engine performance issues are a major cause of downtime.
Causes:
- Blocked fuel injectors or filters.
- Turbocharger or boost leaks.
- EGR valve malfunctions or carbon build-up.
- Incorrect sensor readings feeding the ECU.
Solution:
- Scan with Jaltest to identify injector, turbo, or sensor faults.
- Run a cylinder cut-out test to isolate misfiring cylinders.
- Check boost pressure, air intake, and exhaust systems for leaks.
Tip to Fix Faster: With Jaltest’s real-time data monitoring, you can compare fuel pressure, turbo boost, and air/fuel ratios instantly, confirming whether the issue is mechanical or electronic.
Why Jaltest is the Ultimate Tool for Off-Highway Diagnostics
What makes Jaltest invaluable for construction equipment workshops and operators is its wide manufacturer coverage. With a single tool, you can diagnose and repair vehicles from all major brands, including:
- Caterpillar
- Kobelco
- Doosan
- Liebherr
- BOMAG
- JCB
- Komatsu,
- Volvo CE,
- Case
- And many more
Instead of juggling multiple OEM tools, Jaltest gives you one platform with:
- Fault code reading/clearing with guided troubleshooting.
- Live data and actuator tests for confirmation.
- System calibrations and adaptations across engine, transmission, hydraulics, and emissions.
- OEM-level coverage across leading off-highway manufacturers.
Off-highway machinery will always face tough working conditions, but diagnosing and fixing faults doesn’t have to be slow or complicated. With Jaltest Diagnostics, workshops can cut downtime, save money, and keep construction sites moving.
Order Jaltest OHW today at Eclipse and receive unbeatable on-going support from our expert team.
