Cars Simplified: Everything Automotive Explained

Warning Lights

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An alphabetical list of the warning lights you may be able to find on your dashboard, though a lot of these will vary based on your car brand and features. These lights may also be called "Tell-Tale" lights, or the more derogatory "Idiot" lights. On most vehicles, all of the available warning/status lights will briefly illuminate so that you can tell that the lights themselves are working. Warnings that would appear on-screen will typically not display.

ABS Fault

An ABS light will illuminate when there is a fault with the Antilock Braking System or it has been turned off. While vehicles have been produced without anti-lock brakes in the past, and can typically function without an ABS system, it can be very dangerous to suddenly lose it and have to stop abruptly because not only will the driver expect different vehicle behavior, they are likely not experienced in how to handle locked-up wheels, and will likely keep them locked up, unable to steer around a collision when they otherwise would have been able to. On early vehicles equipped with ABS, the ABS light may also indicate other brake related issues, such as low brake fluid levels.

Auto P Off

A light that says "Auto P Off" (perhaps stylized "Auto (P) Off", where the P is within a circle and/or brackets) is an indication that the automatically-engaged automatic parking brake is off, either by being turned off by a user or by fault. This light is typically amber or red.

This light being on combined with another parking brake fault light may indicate a more specific problem, such as clarifying that it is a fault instead of a setting that has been selected.

Battery/Charging System

This icon is usually depicted as a car battery with the positive (+) and negative (-) symbols shown inside the main box section. Although it does depict a battery, it is actually an indication that the charging system is malfunctioning. While this could be caused by a bad battery, it is more often caused by a malfunctioning alternator (or generator on very old vehicles). The true cause of the illumination must be diagnosed in order to prevent replacement of the wrong part.

Brake Warning, General

This may be one of the more vague-looking symbols, but this is a general brake warning symbol. This exclamation point in a circle with brackets on either side will alert you to a brake issue that must be diagnosed.

This may be a serious issue that may mean the vehicle will do something unsafe immediately, making it potentially unsafe to even drive to the mechanic. Have this diagnosed and/or moved by a professional.

Check Engine (CEL) or Malfunction Indicator (MIL)

Likely the most well-known trouble light on the dashboard, the check engine light generally means there is an engine, drivetrain, or emissions trouble code that can be read with an on-board diagnostics tool. This light can mean an incredibly broad amount of things, and multiple things at the same time without it being clear that multiple issues have set off the light. This light is most commonly amber/yellow, but may be other colors.

A flashing check engine light means a critical failure that may promptly cause significant damage has occured.

Cruise Control Ready/Active

The cruise control light's purpose will differ based on what the manufacturer wants to indicate, but it generally indicates that the cruise control is ready to use or active. It is typically green, and will often depict a triangle arrow pointing to a spot on a dial, symbolizing a selected speed on a speedometer.

While sometimes a symbol is used, the light may just be the word "CRUISE" or a more descriptive text variant of that.

Door Ajar

A door ajar warning may appear as a red or amber light (typically red) but it may also be shown on a screen as a picture of your vehicle with its door open. The the case of the latter, it almost always shows the door or doors in particular that are open, sometimes even showing just how open they are. No matter the means of display, it is often accompanied by a loud warning tone when the driver attemps to move the vehicle (forward or reverse) with a door ajar.

A door ajar light may share duty with trunk/boot/hatch/hood/other panel ajar lights, especially on older vehicles where a simple on/off switch to a light circuit keeps the wiring simple. A door switch that intermittently connects/disconnects may randomly set off a vehicle security alarm.

Door Latch Replacement Doesn't Fix Door Ajar Light: Now What?

In this video by , a caller had a door ajar light come on in a 2004 Chevrolet Silverado 4-door, and has replaced the latch with an integrated door switch. After replacement of the faulty door's latch/switch, the door ajar light still comed on. Larry Perry explains what to do next when encountering this issue!

This clip is from a live show broacast on December 17th, 2022, and this clip was uploaded on January 4th, 2023.


The "eco" light isn't a warning, but lets the driver know they are currently driving economically, or the vehicle is in an economical driving mode. This light is almost always green, and may say "ECO" or simply appear as a leaf.

Some vehicles will have both an "ECO" light and an "eco mode" light, but will usually only have one.

Eco Mode

A more specific version of the "Eco" light, this light specifies that eco mode has been selected or enabled. This light is practically always green, and is often selectable by the driver using a button with the same icon on it.

Some vehicles will have both an "ECO" light and an "eco mode" light, but typically they have just one of them.

Fog Lights On

This light simply indicates that the fog lights are switched on, eliminating the need to look at the switch, which may need to be looked at closely to see which position it is in. It is often green, yellow, or amber, but can sometimes be other colors, especially red when equipped with rear fog lights. It is typically depicted as a light cone emitting slightly downward "light rays" that shine through a line or squiggle, which represents light shining through fog.

Glow Plug

A light appears as a coil, usually forming two visible loops, and will typically illuminate orange/amber/yellow. Upon start-up, a solid illumination of the light means the glow plugs are warming up. A flashing glow plug light occurs when there is an issue with the glow plug system, and may be faulty glow plugs, a failed glow plug relay, a control module issue, or the wiring related to any of these.

A coil plug warm-up light is also called a preheat light.

High Beam On

This light illuminates to let the driver know their high beams are on. Since the high beams are too bright for oncoming traffic, the lights should be shut off when other drivers are approaching. The indicator has historically been bright blue, making it easy to know when it's in use without even looking to see the shape of the indictator.

Lane Keep Assist Enabled/Disabled

Lane keep assist will have an enabled and/or disabled light depending on how the manufacturer feels is the best experience for the driver. Typically, the light that indicates the system is on will be green, and the light that indicates that it is off will be yellow, amber, orange, or red. The light pictogram will often show lanes with forced perspective heading into the distance, with either a car or steering wheel between the lanes.

Low Beam On

A low beam icon turns on when the low beams are actively on. This light tends to be either green, yellow, or amber. The icon tends to look like a light cone emitting lines (beams of light) that point slightly downward.

Oil Pressure Light

This light is often described as a genie lamp, but it is actually an old fashioned oil can that was used to add lubricant to surfaces/parts. This light illuminates when oil pressure is low, and sometimes when the oil level is too low. Incorrect oil viscosity may cause the pressure Low oil level and/or pressure can cause engine damage. This light is typically yellow, amber, or red, and may have two colors depending on the severity of the concern.

Good oil maintenance should be performed regardless of the oil light, as poor oil conditions can occur without this light ever illuminating.

Parking Brake

The parking brake light is there to let the driver know the parking brake is applied, either as a successful application or so the driver can quickly figure out why the vehicle isn't moving much or at all when it should. This light is typically red/orange/amber/yellow, and may illuminate as a different color to distinguish between a fault and an alert.

The light, unless otherwise indicated, is simply an on or off indicator, so a manual/mechanical parking brake could be applied minimally. This is less of a concern with an electronic parking brake.


RAB typically means "Reverse Auto Braking" in the context of a vehicle, and an RAB OFF light will let the driver know that the automatic braking has been diabled or is otherwise inoperable. Because of the complexity of an RAB system, the issue preventing the reverse auto braking may be as temporary as a few seconds, with the light remaining on for just as short of a time. A constant light on, especially when it remains on for many trips, may indicate a problem with the RAB system, or it has been turned off. If the reverse auto braking isn't functioning, it will not make any attempt to apply the brakes to stop the vehicle before a potential collision. The light is typically just text, reading RAB OFF in red, orange, or amber.

Since the braking for this system is engaged with the ABS unit, any fault that will turn on the ABS light will also turn on the RAB light on a vehicle equipped with RAB.


This is typically a user-toggled light, but it also serves to let you know the traction control is no longer operational when it is having an issue and cannot do its job. A faulty sensor such as a wheel speed sensor or computer failure may cause this, but with many causes, this issue must be diagnosed. Sometimes the problem may be as seemingly-unrelated as installing LED replacement bulbs in the brake/taillights. This light is normally yellow/amber/red, but may be other colors, and may be different colors depending on if it is a setting or a fault.

This may appear as a pictogram of a car with skid marks behind it, "TRAC OFF" (usually in all capital letters, but not always), a combination of the two, or a more specific design that is unique to the brand/manufacturer. On vehicles with a button that turns off the traction control, this light may illuminate, but some level of traction control may still be in effect; however, the amount varies by make/model and will not behave the same as a traction control issue.

Trunk/Boot Ajar

A trunk/boot ajar light will warn the driver that their trunk or boot is not properly latched, or is completely open. This may take the form of a yellow/amber/red light, or a graphic on a screen. There may be a warning audible tone, but since sometimes the trunk/boot is left open to transport larger cargo, it is far less common to have an audible warning tone than with a door ajar warning.

Some vehicles equipped with a boot/trunk will not have this warning, but it has been a very long time since this has been the default way vehicles are built.

Wiper Fluid Level Low

When this light comes on, the wiper fluid level is probably low, or the sensor that detects the level may be faulty. A wire or computer issue could still be at fault, though, so be sure to diagnose the issue before purchasing replacement parts. It could even be that everything is working, but there is a leak in the washer fluid tank and the light comes on when the level is low again, even though not enough washer fluid has been used to merit the low level. This light is usually yellow/amber or a text-on-screen warning.

Wrench/Spanner Light

A wrench/spanner light may mean that a scheduled service is due. This light it typically orange, but may appear as another color.

Not all service due indications show up as this wrench/spanner icon.

Further Information

While we strive for accuracy here, the lack of standardization in the icon designs and what they mean may lead to incosistencies or inaccuracies in certain vehicles. For the most accurate information for your vehicle, check the owner's manual. This list currently contains descriptions for 21 warning lights. Colors of lights typically range from green, not a big concern, to yellow/amber, moderate concern, and then to red for the biggest concern, but these too are not standardized.