We know the sinking feeling when you see the BMW check engine light glaring back at you, especially when your car is from the new inventory.
It’s like a cryptic message from your car’s inner workings, leaving you wondering what’s gone awry beneath the hood. Anything from a faltering catalytic converter to a grumpy oxygen sensor could have triggered this ominous bulb.
But fear not!
We’ll decipher the common signals, guide you through what actions to take when that light comes on, and even teach you how to perform a reset.
This Article Contains:
- What Does the Check Engine Light on BMW Mean?
- What Causes the BMW Check Engine Light to Turn On?
- Is it Safe to Drive with a Lit Check Engine Light?
- What to Do if Your BMW Check Engine Light Turns On?
- How to Perform a Check Engine Light Reset?
- How Much Does a BMW Check Engine Light Diagnosis Cost?
Let’s begin.
What Does the Check Engine Light on BMW Mean?
The check engine light is part of your BMW’s onboard diagnostic system, which alerts you about issues within your vehicle’s engine or emissions system that require immediate attention. This warning light can appear in different ways on a new BMW — as the text “Check Engine,” a symbol depicting the engine, or both. It usually illuminates in amber or red color.
However, the BMW check engine light is the most ambiguous warning light on your vehicle. It can be triggered by something as simple as a loose gas cap or more severe issues that require prompt auto repair, like engine misfires. Irrespective of the cause, reading the code registered by the Engine Control Unit (ECU) can help with an accurate diagnosis.
That said, as a car owner, you should know a few common causes that usually trigger this alert.
Note: BMW’s electric inventory (like the new BMW IX inventory) doesn’t have a check engine light as BMW electric vehicles don’t have an engine.
What Causes the BMW Check Engine Light to Turn on?
An illuminated check engine light doesn’t always mean you need an engine repair. It could also indicate that the cooling system isn’t functioning properly, causing the engine to overheat, or that you need transmission repair.
However, if you have an OBD-II scanner, you’re one step closer to solving the problem. Most BMW-certified new vehicles, including all cars in the BMW X2 and the new BMW I5 inventory, and pre-owned vehicles offer OBD-II scanner compatibility.
Here are some common reasons and related scan codes to clarify what the automotive issue might be:
1. Gas Cap Issues
The gas cap helps maintain fuel pressure inside the tank. However, a broken, missing, or loose gas cap negatively affects this ability. When fuel pressure drops, the Engine Control Unit (ECU) triggers the check engine light and presents a P0440 fault code. You may also notice reduced fuel economy.
Tip: Checking a loose gas cap is a good starting point before heading for a BMW value service.
2. Failing Catalytic Converter (CAT)
The catalytic converter helps convert harmful carbon monoxide into carbon dioxide.
However, an unkempt vehicle tends to clog the catalytic converter over time. This affects your vehicle’s fuel economy and performance, which triggers the check engine light and the P0420 trouble code.
Remember: Replacing the catalytic converter is an expensive repair, so pay attention to failing CAT symptoms. Also, BMW electric vehicles don’t have a catalytic converter.
3. Fouled Spark Plugs or Spark Plug Wires
Spark plugs ignite the air-fuel mixture in the combustion chamber of your vehicle. They use the high voltage running through the spark plug wires from the ignition coil. Eventually, carbon deposits build up on them, sometimes due to too much fuel (unburned fuel) in the mixture.
When this happens (or when the ignition coil breaks), the spark plugs don’t work effectively and cause engine misfiring, which triggers the check engine light. In some instances, the spark plug wires can also malfunction.
Your ECU will register a P0300 or P0171 fault code if this occurs.
4. Faulty Oxygen Sensor (O2 sensor)
The oxygen sensor (O2 sensor) is another essential part of the emissions system and one of the most common causes of a lit engine light. It relays information about unburned oxygen levels in the exhaust system to the ECU so that it can control the air-fuel mixture.
However, when the oxygen sensor breaks (often due to long-term exposure to hot exhaust gases), it provides inaccurate unburned oxygen readings.
Due to faulty oxygen sensor readings, the ECU produces an unbalanced air-fuel mixture in the engine, causing a misfire and an illuminated check engine light. Depending on the problem, your ECU will register the P0175, P0713, P0171, or P0162 check engine light codes.
5. Faulty Mass Airflow Sensor (MAF)
The mass airflow sensor (MAF) reads the amount of air entering the engine and sends the information to the ECU so it can produce the right air-fuel ratio in the engine.
How does the MAF break?
This is primarily due to exposure to dirty air. If this occurs, your ECU will register a P0101 diagnostic trouble code.
6. Low or Dead Battery
Your car’s battery is essential for powering several systems, including the car’s computer system. If the computer system doesn’t receive enough power, it may trigger the check engine light. Your ECU will register a P0562 diagnostic trouble code indicating low voltage.
7. A Vacuum Leak
Your BMW’s vacuum hoses push fumes through the engine. This ensures an adequate air-fuel mixture and reduces harmful emissions.
When there’s a leak, too much air enters the air-fuel mixture, causing misfiring and an active or flashing check engine warning light. Your ECU will indicate the P0171 or P0174 check engine light codes.
8. Others
Some lesser-known but possible triggers of a BMW check engine light include:
- Faulty engine coolant temperature sensor
- Worn throttle position sensor
- Clogged or broken exhaust gas recirculation (EGR) valve
Now you know the causes of a BMW check engine light, but should you continue driving or pull over?
Keep scrolling to read more.
Is it Safe to Drive with a Lit Check Engine Light?
Short answer: No!
Driving with an illuminated BMW check engine light can be risky, depending on the underlying cause.
In some cases, the issue triggering the check engine light could be minor and pose no immediate danger. However, in other instances, it could indicate a more severe problem that may require an immediate engine repair.
Ignoring a check engine light service and continuing to drive could further damage your vehicle, reduce its performance, or even pose safety hazards.
So what do you need to do next?
What to Do if Your BMW Check Engine Light Turns On?
Your next course of action depends on how the check engine warning light illuminates. In most cases, you should take your car for a BMW service.
1. Check Engine Light Illuminates Under Certain Circumstances
If your check engine light warning light turns on and off, note any changes in vehicle performance. A difference in performance indicates something is likely to fail soon. So, drive your car as little as possible and take it to a certified mechanic immediately.
2. Check Engine Light Is Constantly On
A permanently lit check engine warning light means a problem needs fixing or you need to service engine soon. As check engine light problems vary in severity, you may not notice a difference in performance.
However, you should still visit a BMW service center to avoid additional issues.
3. Flashing Check Engine Light While Driving
A check engine light flashing is a serious warning sign. In this case, pull over immediately and call a mechanic to ensure your safety.
4. Check Engine Light Is on with Performance Issues
Consistent lowered performance accompanied by the check engine warning light may indicate your vehicle is in “limp mode.” This is a feature of modern vehicles that protects them from further damage. Get your vehicle towed or have a certified mechanic come to your door, but avoid driving at all costs.
You took your car to a certified mechanic for a BMW repair.
But what if the light stays on afterward?
How to Perform a Check Engine Light Reset?
Most BMW check engine lights reset automatically after the problem is addressed. If yours is still on, it may indicate something else needs attention. You can return your vehicle to the BMW service center or use the OBD II scanner to check for further problems.
If you’re certain there isn’t an issue, you can reset the check engine light by disconnecting the negative battery cable for one minute. Then, reconnect it and turn on your vehicle.
Whether you take your vehicle back to the mechanic or are taking it in for the first time, it’s always better to know the costs involved beforehand.
How Much Does a BMW Check Engine Light Diagnosis Cost?
Irrespective of whether you own a compact BMW 3 series or a hybrid from the new BMW I5 inventory, the check engine light diagnosis will usually range from $90 to $120.
The cost to service engine may vary depending on the severity of the problem and the number of service hours. A gas cap issue is inexpensive, but a parts center may charge almost $2,500 for a new catalytic converter.
The warranty may cover these costs for certified pre-owned BMW inventory. However, with non-certified pre-owned vehicles, the owner likely pays. This is an important factor when considering BMW-certified offers.
Resolve Your BMW Engine Light with AutoNation Mobile Service
Check engine light problems vary in severity, but a serious issue could cause irreversible damage to your vehicle and risk your safety. So it’s best to get it diagnosed as soon as possible.
Why not protect yourself and your new BMW by having an auto repair service like AutoNation Mobile Service come to you?
We cater to all BMW models, including the BMW 3 series and BMW X2 cars. We are also equipped to handle other makes, like Audi repair or Mercedes repair.
Plus, we offer easy online booking and a 12,000-mile | 12-month warranty on all repairs, including brake repair, engine repair, clutch repair, or transmission repair.
Reach out for a BMW repair quote today.