In modern trucks, the dashboard is more than a speedometer and tachometer. It is an early warning center for failure:
- for the driver – a glowing light and a message,
- for the fleet owner – the cost of a stop or a controlled replacement of a specific part,
- for the workshop – a clue as to where to start diagnosis.
Table of Contents
Well-interpreted lights allow you to:
- distinguish the situation “STOP, tow truck ” from “get to the base and schedule a repair” ,
- associate the light with the error code and the real cause,
- prepare for the replacement of specific components:EGR, EGR cooler, DPF, AdBlue pump, NOx sensor, air valve, turbine with VTG adjuster, BPV valve, transmission selector, fuel injectors, alternator….
Throughout this process it is not only good diagnostics that counts, but also access to reliable, new and regenerated parts. This is exactly what Arcoore specializes in – from EGR and AdBlue systems to turbines, gearbox selectors and fuel system components.
The colors of the controls on a truck – a quick download
Red lights – STOP, engine protection and safety
A red light – whether for the engine, brakes, pneumatics or charging – means:
“Stop as quickly as possible in a safe place – further driving may damage components or compromise safety.”
The most common concerns are:
- engine oil pressure,
- coolant temperature / overheating,
- brake system and pneumatics (low pressure),
- alternator charging,
- serious transmission errors.
Ignoring red lights usually means:
- engine seizure,
- failure of the braking system or pneumatics,
- electrical failure instead of “just” an alternator or valve.
Yellow / orange lights – service ASAP, but don’t panic
A yellow light indicates that:
- the system is operating in emergency mode or with limited efficiency,
- the malfunction is usually related to emissions, electronics, sensors, ABS/EBS, ESP, supercharging (turbo, VTG, BPV) or transmission.
Examples:
- yellow check engine light,
- emission / DPF / AdBlue light,
- transmission, supercharging system, fuel system warnings.
From the fleet point of view:
- The yellow light should not be ignored, but you do not always need to call a tow truck right away – this is the moment to plan diagnostics and prepare Arcoore parts.
Green, blue, white lights – status and information
They usually inform about:
- active lights (low beam, high beam, fog lights),
- activated functions (cruise control, retarder, assistants),
- driving modes.
The problem begins when the “green” statuses disappear and yellow or red warnings appear .
From the light to the error code – how to go from the light to a specific part?
The light itself is only the first step. A typical diagnostic diagram:
- Light on the dashboard – color + pictogram (engine, DPF, AdBlue, brake, transmission, turbine, battery).
- Text message – for example, “Malfunction of the exhaust aftertreatment system”, “Malfunction of the transmission”, “Low power – supercharging system”.
- Error code from the tester:
- OBD-II (e.g. P02xx family for injectors, P04xx for EGR, P20xx for AdBlue, P0234/P0299 for supercharging),
- Or a MID/SID/PID/FMI record typical of trucks.
- Analysis of symptoms – loss of power, failure mode, jerking, rough running, smoke, fluid loss, shifting problems.
- Parts selection – instead of replacing half the car:
- EGR valve, EGR cooler,
- DPF filter,
- AdBlue pump/dispenser, NOx sensor,
- turbine with VTG adjuster, BPV valve,
- transmission selector,
- injectors,
- air valves, alternator, etc.
This is when Arcoore provides a specific part by OE number and symptoms, not a “random replacement”.
Main groups of controls and faults – what usually falls and what parts are worth having on hand?
Engine, oil, temperature – when every minute costs money
What does the driver see?
- A red oil light,
- red temperature light,
- red “STOP ENGINE” sign.
Possible errors:
- “Low oil pressure”,
- “High coolant temperature”,
- “Engine protection – power derate”.
Causes:
- real drop in oil pressure (pump, teat, low level),
- muddled, clogged radiators – cooling stops working,
- leaks in the cooling system, cracked radiator, faulty thermostat, water pump.
Consequences of ignoring:
- seizing of the engine,
- very expensive overhaul instead of a simple cooling system repair.
Parts most often involved:
- liquid coolers, intercoolers, hoses, thermostats, water pumps,
- indirectly – overheating also affects the turbine, EGR, DPF.
Arcoore:
offers liquid coolers, charge air coolers (intercoolers) and cooling system components for popular trucks.
Brakes, ABS, EBS, pneumatics – kit safety
Dashboard lights:
- red brake/low air pressure light,
- yellow ABS/EBS light.
Errors:
- “Low air pressure in circuit 1/2”,
- “Wheel speed sensor signal faulty”,
- “EBS control unit fault.”
Causes:
- air leaks, disconnected quick couplings,
- worn compressor, problem with the dryer,
- defective wheel speed sensors, harnesses, EBS controller.
Parts:
- air valves,
- dryers and cartridges,
- ABS sensors, EBS modules.
Arcoore provides:
pneumatic valves and components, dryers, ABS sensors – everything to eliminate errors and restore full efficiency of brakes.
Exhaust emissions – EGR, EGR coolers, DPF, AdBlue/SCR
This is where fleets lose the most if they drive “until something red lights up.”
EGR and EGR coolers – a classic of the yellow check engine light
Symptoms:
- yellow check engine light,
- emissions/recirculation messages,
- loss of power, smoke, uneven operation, fluid loss.
Errors:
- “EGR flow insufficient/excessive”,
- “EGR position fault”.
Causes:
- jammed, coked EGR valve,
- leaking/broken EGR cooler – exhaust gas enters cooling system, fluid disappears, controller reports abnormal emissions.
Parts:
- EGR valve (new/regenerated),
- EGR cooler,
- gaskets and mounting parts.
Arcoore specializes in:
Regenerated EGR coolers and EGR valves and throttles for many brands of Euro 5/6 trucks.
DPF – the particulate filter that doesn’t like short runs
Symptoms:
- yellow DPF light,
- “DPF full”, “Regeneration required” messages.
Errors:
- “DPF soot level too high”,
- “DPF regeneration not completed”.
Causes:
- driving with a predominance of short distances and stops,
- faulty temp/pressure sensors,
- leaks in the intake/exhaust.
Parts:
- DPF/FAP filter (new or regenerated),
- differential pressure sensor,
- exhaust gas temperature sensors.
Arcoore offers:
new and regenerated DPF, as well as temperature and pressure sensors for the most popular trucks.
AdBlue / SCR – power and speed limitation
Symptoms:
- yellow (sometimes flashing) AdBlue/SCR light,
- exhaust aftertreatment system fault message,
- counter for power/speed limitation.
Errors:
- “AdBlue pressure too low”,
- “SCR efficiency below threshold”,
- “NOx sensor fault”.
Causes:
- worn out AdBlue pump,
- clogged / damaged AdBlue dispenser (injector),
- dead NOx sensor,
- dirty tank, bad fluid, freezing.
Parts:
- AdBlue pump,
- dispenser/injector,
- NOx sensors, exhaust gas temperature sensors.
Arcoore:
AdBlue pumps and injectors (new and regenerated), NOx sensors and exhaust gas temperature sensors – ready-made kits for fast SCR system restoration.
Electrical and charging – red battery light
Symptoms:
- red battery light.
Errors:
- “Generator charge fault”,
- “Low system voltage”.
Causes:
- defective alternator,
- broken/worn belt,
- weak earths, sluggish clamps.
Parts:
- alternator,
- belt, pulleys,
- ground wires.
Arcoore supplies:
alternators and accessories, which restore proper charging and extinguish the red light.
Air suspension, ECAS, lift axles
Symptoms:
- suspension light, ECAS errors,
- uneven condition, lifting axle problem.
Causes:
- leaks from bellows and hoses,
- defective height sensors,
- ECAS valves/electric valves, controller.
Parts:
- bellows,
- ECAS valves and solenoid valves,
- height sensors.
Arcoore offers:
air suspension components – valves, fittings – to stabilize the vehicle and remove ECAS errors.
Supercharging system – turbos, VTG adjusters and BPV valves.
Yellow check engine light + no power, failure mode, supercharging messages are a daily occurrence.
What does the driver see?
- Yellow check engine light,
- a message like “Supercharging system fault” / “Low boost pressure” / “Overboost”,
- a pronounced drop in power, sometimes whistling, swishing, smoke.
Typical errors:
- “Boost pressure too low/high”,
- “Turbocharger control position fault”,
- “Charge air system leakage”.
Most common causes:
- VTG-regulated turbocharger
- jammed exhaust gas controllers (carbon build-up, corrosion),
- defective VTG adjuster (electric/pneumatic),
- excessive mechanical clearances in the turbine.
- BPV (bypass / blow-off / wastegate) valves.
- valve suspended in one position,
- leakage in vacuum/pressure control,
- defective actuator.
- Intake system
- leaking hoses, broken intercooler,
- damaged bands, ferrules.
Parts to replace:
- complete turbines (new or regenerated),
- VTG adjusters (turbocharger actuators),
- BPV valves / boost control valves,
- air ducts and coolers (intercoolers).
Arcoore:
Regenerated turbochargers, VTG actuators and boost control valves (BPV) for many truck models are available – ideal for common boost errors and yellow check engine light.
- All products
Regenerated DPF particulate filter for Iveco Stralis Hi-Way Euro 6 – 5802039934
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New twin-cylinder air compressor for Mercedes Actros MP5 Euro 6, LK4972
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Regenerated DPF particulate filter for Iveco Stralis – 5802039929
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Regenerated EGR valve with controller for Volvo FH Euro 6, 24328031
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Transmission and selectors – when the transmission light comes on and the car stays in “N”
In modern automatics and automated transmissions, more and more often the source of the problem is not the transmission itself, but the selector / control module.
What does the driver see?
- The gearbox light,
- messages like “Gearbox fault”, “Transmission malfunction”,
- the transmission stays in one gear or in the “N” position, does not want to engage the gear.
Typical errors:
- “Gear selector fault / shift module fault”,
- errors of gear positioning, selector position sensors,
- controller-selector communication errors.
Most common causes:
- wear or damage to the gear selector (electro-pneumatic, mechatronic),
- problems with position sensors, harnesses, connectors,
- defects in the positioning mechanism.
Parts:
- gearbox selectors (e.g. type WABCO GS3.3, GS3.6, etc.),
- position sensors, harnesses, connectors,
- pneumatic-hydraulic components controlling the gear shift.
Arcoore:
offers gearbox selectors and control components for popular trucks, so that many faults marked only as “gearbox fault” can be solved by replacing the selector module rather than a major overhaul of the gearbox.
Fuel system – fuel injectors
Problems with fuel injection very often manifest themselves as yellow check engine light, jerking, smoke, difficult starting.
What does the driver see?
- yellow check engine light,
- messages about engine trouble, loss of power,
- sometimes intense white, gray or black smoke from the exhaust.
Typical errors:
- “Cylinder contribution/balance fault”,
- “Injection timing fault / injection quantity fault”,
- Common rail rail pressure errors.
Most common causes:
- worn fuel injectors (leaking, leaking, blocked),
- dirt in the fuel system, poor fuel quality,
- problems with the high-pressure pump, pressure regulator.
Parts:
- fuel injectors (common rail),
- high pressure pump components,
- fuel lines, CR trim.
Arcoore:
can offer fuel injectors and fuel system components compatible with popular truck units – allowing you to solve engine light problems without “shooting” at random.
Simple fleet procedure – how not to burn through the cash on the indicator lights
Instead of “Something lights up, drive to the service center, let’s see.”
A short, repeatable scheme is better:
- The driver takes a picture of the dashboard – light + message.
- Notes mileage, load, driving conditions.
- Service reads error codes and connects them to symptoms.
- On this basis:
- you decide whether it’s the trailer (red STOP), or getting to the base (yellow),
- you order specific parts – EGR, DPF, AdBlue, turbine/VTG/BPV, selector, injectors, air valves, alternator.
At this point, it’s good to have a partner who:
- will quickly match the part by OE number and fault description,
- will offer reasonably priced new and regenerated parts,
- has experience typically in trucks.
Such a role can be fulfilled by Arcoore.
FAQ
What does a yellow check engine light on a truck mean?
Most often it indicates a malfunction in one of the systems that work with the engine: EGR, DPF, AdBlue, supercharging system (turbine, VTG adjuster, BPV valve), fuel system (injectors) or sensors. Usually you can get to the base, but the vehicle may enter a failure mode. In practice, it’s a good idea to read the fault code and be prepared to replace a specific component – Arcoore can supply EGR coolers, DPFs, AdBlue pumps, NOx sensors, turbines, selectors and injectors.
A yellow AdBlue light and a drop in power - can you keep going?
For a while, yes – most trucks allow you to reach the service, but with no response, the controller limits power and speed. Typical causes are the AdBlue pump, dispenser or NOx sensor. The solution is to diagnose the SCR system and replace the worn components – pump, metering device, NOx sensors – available from Arcoore.
Yellow check engine light and lack of power, but DPF and AdBlue are “clean” - what next?
Very often the problem then lies in the supercharging system (turbine, VTG adjuster, BPV valve) or in the fuel system (injectors). The tester will show errors in boost pressure, turbo control or cylinder operation. In such a situation, it is worth checking the tightness of the intake, the condition of the turbine, the efficiency of the VTG adjuster and BPV valve, as well as the injectors. Arcoore can supply turbines, VTG actuators, BPV valves and fuel injectors.
Transmission light and inability to shift into gear - is the transmission always to blame?
Not always. In modern transmissions, very often the problem is with the selector / control module, and not the gears themselves. Errors like “gear selector fault” point precisely to the selector, position sensors or harnesses. In many cases, replacing the gear selector (e.g. WABCO GS) solves the problem without taking apart the entire transmission. You can find these types of selectors in Arcoore’s offer.
How to use the indicator lights to reduce fleet costs?
Treat the indicator lights as an early warning:
- red = protection of engine, brakes, pneumatics – a trailer is cheaper than an overhaul,
- yellow = scheduled service and replacement of typical wear items:EGR, DPF, AdBlue, turbines/VTG/BPV, selectors, injectors, air valves, alternators.
With a partner like Arcoore, you can quickly select the right parts (including regenerated) and put out the lights without overpaying.
