Dashboard Warning Lights Explained in Plain English

Color is the first clue. Red usually means a problem that can damage the engine or affect your ability to stop, so find a safe place to pull over. Amber or yellow means the car detected a fault that needs attention soon but usually lets you finish a short trip carefully.

A light tells you which system reported a problem. It does not tell you which part failed. That is why we scan and inspect before quoting a repair, and why guessing from the symbol alone often buys the wrong part.

These lights call for a safe stop and a phone call, not a drive across town. Continuing can turn a moderate repair into a major one.

• Oil pressure (red oil can): the engine may not be getting oil. Stop and shut it off.
• Engine temperature (red thermometer): the engine is overheating. Stop, let it cool and do not open a hot radiator cap. See cooling system and radiator.
• Brake warning (red, often "BRAKE" or a circle with "!"): check that the parking brake is off. If it stays on, the fluid may be low or the system may have a leak.
• Flashing check engine light: a severe misfire that can overheat the catalytic converter. Slow down and get it checked right away.

These lights usually allow careful driving to the shop, but they should not be ignored for weeks.

• Steady check engine light: a stored fault code. It could be a loose gas cap or a failing sensor. A check engine light scan reads the code and the conditions when it set.
• TPMS (horseshoe with "!"): a tire is low, or a sensor has failed. Check pressures first.
• ABS: the anti-lock system has a fault. Normal braking usually still works, but anti-lock may not.
• Battery or charging: the charging system is not keeping up. The car may run until the battery drains, so do not plan a long trip.
• Airbag: the system found a fault and may not deploy in a crash. Get it checked before carrying passengers you worry about.

A steady TPMS light usually means at least one tire is low. A light that flashes for about a minute and then stays on often means a sensor or system fault. Temperature swings can trigger it on cool mornings when a tire is right at the edge.

1. Check all four tires cold with a gauge and set them to the door sticker number.
2. Drive a few miles. Many cars clear the light once pressure is correct.
3. If the light returns, the tire may have a slow leak or a sensor may need service.

Our TPMS service page covers sensor testing and programming.

A code points to a circuit or a condition, not a part. An oxygen sensor code can come from a wiring issue or an exhaust leak, and replacing the sensor will not fix either one. A scan with freeze frame data shows what the engine was doing when the fault set, which narrows the cause.

We tell you up front if a diagnostic charge applies before we start. Then we show you what we found, write the estimate and separate needs from wants.

A few details save diagnosis time and help us tell you whether to drive in or stop.

• Which light, its color, and whether it is steady or flashing
• When it came on: cold start, highway speed, after fueling, after a bump
• Any change in how the car drives, sounds or smells
• Whether the light has come and gone before

Call (909) 608-7699 with that list, or add it to a booking request.

Hybrids and EVs share many lights with gas cars, including TPMS, ABS, brake and airbag. They add their own symbols for the high-voltage system, reduced power and charging. A high-voltage warning belongs with a specialist, while tire, brake and 12-volt battery lights are work we handle in our bay.

A weak 12-volt battery can make these cars show several unrelated lights at once, or refuse to go into ready mode. Testing that small battery is a sensible first step before anyone suspects the expensive parts. Orange high-voltage cable repairs are referred to a specialist.

A light that appears just after fueling or shop work often has a simple link to what was done. A loose gas cap can set an evaporative system code. A disconnected battery can reset modules. Swapped tire positions can confuse some TPMS systems until they relearn. Tell us what happened just before the light appeared.

• After fueling: tighten the cap until it clicks and drive a few days. If the light stays on, get it scanned.
• After battery work: some cars need a relearn for idle, windows or steering angle.
• After a rotation or new tires: some TPMS systems need sensor positions relearned.
• After any repair: call the shop that did the work first and describe the light.

Generally no. A lit check engine light is treated as a failure during a California Smog Check, and readiness monitors that have not finished running can also stop the test. Clearing codes right before the test tends to backfire, because the monitors reset too. Find and fix the cause first, then drive normally so the monitors can complete.

The Bureau of Automotive Repair (opens in a new tab) explains Smog Check rules for California drivers.