Dashboard Indicator Lights Explained: A Driver’s Guide

Dashboard indicator lights are symbols on a vehicle’s dashboard designed to capture the driver’s attention and communicate essential information about the vehicle’s operational status or system malfunctions. They are crucial for safe and efficient vehicle operation, prompting drivers to take immediate action when necessary and encouraging regular maintenance. The International Standards Organisation (ISO) has standardised these symbols with universal colour codes to ensure they are language-independent and understood across different vehicle makes and models.

How do the colours of warning lights indicate urgency?

The strategic use of colours (yellow/amber, orange, and red) on dashboard indicator lights signifies different levels of urgency. Red lights typically indicate a serious problem that requires immediate attention, often advising the driver to stop the vehicle safely and not continue driving. Amber or yellow lights suggest that action is required soon, but the issue might not be as immediately critical as a red light, sometimes allowing the driver to continue driving cautiously to a service centre or to check a fluid level.

What are some common red warning lights and what actions should be taken?

Red warning lights generally signify critical issues that require immediate attention and often mean you should stop driving. Examples include:

• Brake system/fluid level: If red, the brake fluid level is too low or there’s a fault. Do not continue driving.
• Engine temperature: If red, the engine is overheating. Stop the engine immediately and contact a retailer.
• Engine oil pressure: If red, oil pressure is too low. Stop the engine and contact a retailer.
• AdBlue level (diesel engines): If red, the AdBlue level is too low, and the engine will not restart once turned off. Stop in a safe, flat area and top up AdBlue.
• Steering wheel (power steering): If red, there’s an immediate fault requiring retailer attention.
• Airbag system and seat belt tensioners: Indicates a fault requiring immediate inspection by a retailer.
• Electronic parking brake: If it remains illuminated after release, or if a malfunction is indicated while driving, seek assistance.
• Alternator malfunction/electrical system malfunction: Indicates a problem with the charging system or overall electrical system. Do not continue driving and contact a retailer.
• Brake pads worn: Indicates the brake pads have reached their wear limit and need checking/replacement.

What do amber/yellow warning lights indicate, and how should I respond?

Amber or yellow warning lights typically indicate less immediate, but still important, issues that need attention soon. Response usually involves checking something or driving carefully to a service centre. Examples include:

• Brake fluid level: If amber, the level is too low or there is a fault; consider stopping.
• Engine temperature: If amber, the engine is getting warm; consider stopping to allow it to cool.
• Engine oil level: If amber, the oil level is too low; check and top up as soon as possible.
• Steering wheel (power steering): If amber, take the vehicle to a retailer soon. If it goes away after an engine restart, no immediate visit is needed.
• Tyre pressure: Indicates low pressure in one or more tyres. Stop safely, check and correct tyre pressure, and replace damaged tyres if necessary.
• Electronic Stability Control (ESC) or Anti-Lock Braking System (ABS): Indicates a fault or deactivation; drive carefully to a retailer.
• AdBlue level (diesel engines): An amber light typically appears when there are about 1,000 miles of range left. It requires action (refilling AdBlue) before it turns red and prevents engine restart.
• Malfunction Indicator Lamp (MIL) / Check Engine Light: Can indicate an engine control malfunction. Often, the most common cause is an improperly closed fuel filler cap. Check and replace the cap; if the light persists, contact a retailer.
• Glow plug preheating (diesel engines): Illuminates when preheating is active before starting. If it flashes while driving, it indicates an engine control malfunction.
• Washer fluid low: Indicates the windscreen washer fluid needs refilling.

What is the EPC light in Volkswagen vehicles and what does it mean?

The EPC (Electronic Power Control) light in Volkswagen vehicles indicates a malfunction in the engine electronics or powertrain. It often accompanies a noticeable reduction in engine power or the vehicle entering “limp mode.” Common causes for the EPC light can be varied and include issues with spark plugs, ignition coils, air filters, camshaft/crankshaft sensors, or even a corroded wastegate on the turbocharger. Due to the wide range of potential causes, it is highly recommended to use an OBD2 scanner or a manufacturer-specific diagnostic tool (like VCDS for VW/Audi) to pull specific trouble codes (DTCs) to accurately diagnose the problem. The EPC light can also interfere with OBD2 port communication in some cases.

What are Diagnostic Trouble Codes (DTCs) and how are they structured?

Diagnostic Trouble Codes (DTCs) are standardised numerical and alphanumeric codes used in vehicles equipped with On-Board Diagnostics II (OBD II) systems. These codes are recorded by the OBD II system when it detects malfunctions in engine management or automatic transmission operation, alerting the driver via the Malfunction Indicator Light (MIL).

DTCs follow a specific structure defined by the Society of Automotive Engineers (SAE):

• First digit: Identifies the system (P for powertrain, B for body, C for chassis, U for future systems).
• Second digit: Indicates if it’s a government-required code (0) or a manufacturer-specific code (1).
• Third digit: Specifies the general area of malfunction (e.g., 1xx/2xx for air/fuel measurement, 3xx for ignition, 4xx for emission control, 5xx for speed/idle, 6xx for computer/output signals, 7xx/8xx for transmission, 9xx for control modules).
• Fourth and fifth digits: Designate specific components and systems.

How well do drivers understand dashboard warning lights, and what factors influence comprehension?

A study involving 2,530 drivers revealed significant differences in familiarity and comprehension of dashboard indicator symbols. While many drivers recognise common symbols, recognition does not always equate to correct comprehension. Symbols with pictorial signs tend to be better understood.

• High Comprehension: Symbols like “Battery Charge Warning” (89.7% correct), “Seatbelt Indicator” (96.1% correct), “Low Fuel Level” (50.4% correct), “Coolant Temperature Warning Light” (54.4% correct), and “Engine Oil Pressure Light” (51.3% correct) were generally well-understood.
• Low Comprehension Despite Familiarity: Some symbols like “Rear Fog Light,” “4×4 gear,” “Washer Fluid Warning Light,” and “Automatic Parking Light” were familiar to drivers, but a majority misinterpreted their meaning (e.g., 72% for Rear Fog Light, 70.6% for Washer Fluid).

What demographic factors influence a driver’s likelihood to comply with preventive maintenance based on dashboard lights?

A study using Generalised Ordered Logistic Regression (GOLR) found that several demographic factors impact a driver’s preventive maintenance compliance when dashboard indicator lights illuminate:

• Driving License Class: Drivers with license classes D and E were significantly more likely (3.7 and 3.1 times, respectively) to comply with preventive maintenance practices compared to those with licenses B and C, who were less likely to comply. This suggests that the type of vehicle a license permits (e.g., larger or more complex vehicles for D and E) might correlate with a greater understanding or responsibility towards vehicle maintenance.
• Regular Dashboard Checks: Drivers who “always” or “sometimes” check their dashboard while driving were significantly more likely (5.3 and 2.2 times, respectively) to comply with preventive maintenance compared to those who rarely or never check. This highlights the importance of habitual monitoring for prompt detection and response to changes in vehicle status.

At Mastertech Poole, we specialise in expert diagnostics, servicing, and repairs for Volkswagen, Audi, SEAT, and Škoda vehicles across Poole, Bournemouth, and the surrounding Dorset area.

Trust your dashboard warning lights to the VAG specialists.