Check Engine Light (engine outline symbol)

The check engine light on an Audi indicates the engine control unit has detected a fault somewhere in the engine or emissions system. It can be triggered by something as simple as a loose gas cap or as serious as a failing oxygen sensor, catalytic converter issue, or fuel system problem.

The most important distinction to understand is whether the light is solid or flashing.
A solid check engine light means the fault has been logged but is not causing active damage right now. The car is typically safe to drive for a short period, but the fault should be diagnosed promptly. Do not put it off for weeks.

A flashing check engine light is a different situation entirely. A flashing light indicates that the engine is actively misfiring right now, meaning one or more cylinders are not burning fuel properly. Unburned fuel is passing into the exhaust system and hitting the catalytic converter, which operates at temperatures high enough to ignite that raw fuel. The resulting heat can destroy the catalytic converter within a few miles of driving. A catalytic converter replacement on an Audi is an expensive repair. A flashing check engine light should be treated as a stop-driving signal. Reduce speed, avoid hard acceleration, and get the car to a safe location. Do not continue driving normally.

Tire Pressure Monitoring Light (exclamation mark in horseshoe symbol)

This light appears when one or more tires have dropped below the recommended pressure. On a Q5 or Q7, the recommended tire pressure is typically printed on a sticker inside the driver's door jamb. Low tire pressure affects handling, fuel economy, and tire wear. It can also indicate a slow puncture. Check all four tires and inflate to the correct pressure. If the light returns quickly after inflation, one tire may have a leak that needs to be patched or replaced.

Service Due Reminder (wrench symbol or SERVICE text)

This is a maintenance reminder, not a fault warning. It appears when the car is approaching or has reached a scheduled service interval based on mileage and oil condition. The car is not in immediate danger, but the service should be scheduled promptly. Delaying oil service past the recommended interval reduces the oil's ability to protect the engine.

Traction Control / Electronic Stabilization Control (car with wavy lines symbol)

This light flashing briefly while driving in slippery conditions is normal. It means the traction or stability control system activated and is doing its job. A momentary flash on a wet road is not a warning. If the light comes on and stays on during dry conditions, it may indicate a sensor fault or a system malfunction that needs to be diagnosed.

The EPC Light

EPC stands for Electronic Power Control. It is a yellow warning light specific to Volkswagen Group vehicles including Audi, and it is one of the most misunderstood lights in the instrument cluster.

The EPC system manages the electronic throttle, which on modern Audis is a drive-by-wire system. Instead of a physical cable connecting the gas pedal to the engine, a sensor in the pedal sends an electronic signal to the engine control unit, which then controls airflow into the engine electronically. When the EPC light illuminates, it signals a fault in this throttle system that could affect engine performance and safety.

The EPC light is different from the check engine light. The check engine light covers a broad range of engine and emissions faults. The EPC light specifically points to the throttle control system, which can include the throttle body itself, the accelerator pedal sensor, the brake light switch, or communication issues between control modules. The two lights can appear together, but they are separate warnings.

Common symptoms when the EPC light appears include reduced engine power, difficulty accelerating, or the car entering a limited power mode sometimes called limp mode where engine revs are restricted to protect the drivetrain. If the EPC light appears and the car is driving noticeably differently than normal, reduce speed and have it diagnosed as soon as possible. If the car is running normally with just the EPC light showing, it is typically safe to drive carefully to a service appointment, but do not delay.

The Slip Indicator / ESP Light (car with squiggly lines)

As mentioned in the traction control section above, a brief flash of this light during slippery conditions is the system working correctly. If the light stays on continuously on dry pavement, it indicates a fault in the electronic stability program. This could be caused by a wheel speed sensor issue, a steering angle sensor problem, or an ABS fault. A persistently illuminated ESP light on dry roads should be diagnosed because it means the stability system is not functioning and will not intervene if the car begins to slide.

The Exclamation Mark Light

Audi uses an exclamation mark symbol in more than one context and in more than one color, which causes significant confusion. The meaning depends entirely on the color and the shape surrounding it.

• A yellow exclamation mark inside a horseshoe or U-shape is the tire pressure monitoring light. It means low tire pressure in one or more tires, as described above.
  
• A red exclamation mark inside a circle with lines on either side is the brake system warning described in the red lights section. This one requires immediate attention.
  
• A yellow exclamation mark that appears with text in the driver information display is typically a general fault notification. The accompanying message in the display will describe what system is affected. Read the message in the cluster rather than guessing from the symbol alone.
  

When in doubt about any exclamation mark light, look at the color first. Red means stop now. Yellow means schedule service.

These lights confirm that a system is running. No action is needed unless you expected a system to be off and it appears active.

Green lights commonly seen on an Audi instrument cluster include the turn signal indicators, the adaptive cruise control active indicator, the lane keeping assist active indicator, and on hybrid or electric models, the ready or drive mode indicator.
Blue lights include the high beam indicator, which confirms the high beams are on, and on some models the exterior temperature warning, which appears in blue when the outside temperature drops near freezing to alert you to potential ice on the road.

Multiple warning lights appearing simultaneously is a specific situation that changes the urgency calculation.

Several lights appearing together when you first start the engine is normal. Audi performs a system check at startup and illuminates various indicators briefly before they go out. If they clear within a few seconds of starting, no action is needed.

Multiple lights appearing while driving is a different matter. When the ABS light and the traction control light illuminate together, it typically points to a shared component issue, such as a wheel speed sensor fault. Both systems use the same sensors, so a single failing sensor affects both warnings. This combination means the ABS and stability control are both compromised. The regular brakes still work, but the electronic safety systems are not active. This should be diagnosed promptly.

If the oil pressure light appears together with the engine temperature light, treat it as a park-it-now situation. Either of those lights alone is serious. Both together mean the engine is under significant stress from multiple directions.

If the battery light appears along with multiple other systems showing faults simultaneously, the most likely cause is a charging system failure. As the battery voltage drops, multiple electronic modules begin behaving abnormally and throwing faults. In this case, the underlying issue is the charging system, not the individual systems showing warnings.

The clearest rule for multiple lights: if any one of them is red, treat the combination as a red situation regardless of what the other lights show. One red light in a cluster of warnings does not make the red light less urgent.