For fleet operators, workshops, and independent technicians, downtime is the enemy. Trucks and trailers are the backbone of the transport industry, but when faults arise, even minor issues can cause costly delays. Knowing the most common truck and trailer diagnostic issues—and having the right tools to resolve them quickly—can save hours of troubleshooting.
In this article, we’ll break down five of the most frequent problems, their causes, and solutions, plus share how Jaltest Diagnostics can speed up the fix.
1. Faulty Sensors (ABS, NOx, EGR, etc.)
The Issue:
Modern trucks and trailers rely on dozens of sensors to feed data to the ECU (Electronic Control Unit). ABS wheel speed sensors, NOx sensors, and exhaust gas recirculation (EGR) sensors are particularly prone to failure.
Causes:
- Exposure to dirt, water, and road salt.
- Wiring harness wear and tear.
- Sensor contamination from soot or oil.
Solution:
- Run a fault code scan with Jaltest Diagnostics to identify which sensor is malfunctioning.
- Inspect wiring and connectors before replacing the sensor.
- Calibrate or reset the sensor using Jaltest’s guided functions.
Tip to Fix Faster: With Jaltest, you can access live data streams from multiple sensors simultaneously, making it easy to spot inconsistent readings and confirm the root cause.
2. Aftertreatment System (DPF & SCR) Issues
The Issue:
Diesel Particulate Filters (DPF) and Selective Catalytic Reduction (SCR/AdBlue) systems are critical for emissions compliance but notorious for clogging and system errors.
Causes:
- Short journeys preventing full regeneration cycles.
- Low-quality fuel or AdBlue fluid.
- Faulty differential pressure sensors or dosing modules.
Solution:
- Use Jaltest to run a forced DPF regeneration if soot levels are too high.
- Check pressure sensors, temperature probes, and dosing units with Jaltest’s test routines.
- Replace filters or modules if regeneration fails repeatedly.
Tip to Fix Faster: Jaltest provides step-by-step troubleshooting guides and regeneration commands, allowing workshops to resolve blocked DPFs quickly without removing the filter.
3. Electrical and Communication Faults (CAN Bus Errors)
The Issue:
Intermittent electrical faults or CAN bus communication errors can shut down entire systems, making them some of the trickiest problems to diagnose.
Causes:
- Damaged wiring looms and connectors.
- Corrosion from water ingress.
- Faulty ECU modules disrupting network communication.
Solution:
- Perform a full system scan with Jaltest to pinpoint where communication is lost.
- Inspect wiring harnesses and connectors visually and with multimeter checks.
- Repair or replace damaged wiring/ECU modules as needed.
Tip to Fix Faster: Jaltest can generate a topology map of the vehicle’s electronic systems, showing which ECUs are active or offline—cutting down guesswork when tracing wiring faults.
4. Braking System Faults (ABS/EBS on Trailers)
The Issue:
Trailer braking systems—whether ABS (Anti-lock Braking System) or EBS (Electronic Braking System)—frequently generate warning lights that can lead to roadside downtime.
Causes:
- Damaged ABS rings or wheel speed sensors.
- Air supply or modulator valve issues.
- Faulty control units or wiring connections.
Solution:
- Connect Jaltest to the trailer’s braking system to read fault codes.
- Test individual solenoids, valves, and sensors with the actuator test functions.
- Replace faulty components and clear error codes.
Tip to Fix Faster: Jaltest includes OEM-level coverage for trailer brands (e.g., WABCO, Knorr-Bremse, Haldex), letting you run precise calibrations and checks instead of relying on trial-and-error repairs.
5. Engine Performance Problems (Power Loss, Misfires, Poor Fuel Economy)
The Issue:
Reduced engine performance is one of the most reported problems in workshops. It can stem from multiple systems, making diagnosis complex.
Causes:
- Blocked fuel filters or faulty injectors.
- Turbocharger boost leaks.
- EGR valve or intake manifold carbon build-up.
- Incorrect sensor data feeding the ECU.
Solution:
- Run a diagnostic scan with Jaltest to identify injector or turbo-related codes.
- Use Jaltest’s cylinder cut-out test to isolate misfiring cylinders.
- Inspect air intake and exhaust systems for blockages or leaks.
Tip to Fix Faster: Jaltest provides real-time engine data, so you can compare fuel pressure, boost levels, and air/fuel ratios on the spot—helping confirm if the issue is mechanical or electronic.
Final Thoughts: Faster Diagnostics = Less Downtime
Truck and trailer faults are inevitable, but with the right approach, they don’t have to mean days of downtime. The combination of good workshop practice and Jaltest Diagnostics can cut repair times dramatically by:
- Providing fault codes with guided troubleshooting.
- Offering live data and actuator tests for confirmation.
- Delivering coverage across truck, trailer, bus, and LCV systems in one tool.
For workshops and fleets, investing in Jaltest means fewer repeat visits, faster fixes, and vehicles back on the road where they belong.
