Buick check engine light comes on when the On-Board Diagnostic (OBD) system detects a problem with the engine, transmission or Evaporative Emission Control (EVAP) System.

Buick check engine light may be referred to as CEL, Malfunction Indication Lamp, MIL, Service Engine Soon or SES light.

Check engine light may come on due to something as simple as a loose or defective gas cap. It can also be an indication of a more serious engine problem, transmission issue or EVAP leak.

The check engine light itself does not provide much information on what is wrong with the vehicle. In this guide, you will learn how to read the fault codes yourself using an OBD-II scanner.

Symptoms

Common symptoms you may notice:

• Engine runs rough or won't stary running
• Check engine light always on or flashing
• Engine overheating
• Lack of power
• Poor throttle response
• Engine noise
• Smoke from the exhaust
• Vehicle won't shift gears, stuck in limp mode

You may not notice any performance symptoms at all if your Buick check engine light is on due to an EVAP leak.

Causes Problems

Common problems that trigger check engine light to come on:

• Worn spark plugs
• Bad oxygen sensor
• Faulty MAF sensor
• Defective Ignition coil
• Clogged catalytic converter
• EVAP Leak
• Loose Gas cap

There are hundreds of possible issues that can trigger the Buick check engine light to come on. To find out why your Buick to check engine light is on, read the fault codes with an OBD-II scanner.

Diagnose Buick Check Engine Light

The following steps will help you learn how to diagnose Buick check engine light.

For this procedure, you will need an OBD-II scanner. If you don't have a scanner you can purchase one online or stop by at your local auto parts store to have the codes read free of charge.

1. Park your Buick and turn off the ignition. Set the parking brakes.
2. Locate the OBD-II port under the dashboard and plugin your OBD-II scanner.
3. Turn on the ignition but do not start the engine.
4. Allow the scanner to turn on and communicate with the vehicle.
5. Read the codes by pressing Read Codes or Read Fault Codes on your OBD-II scanner depending on the scanner. Reach each code to learn more about possible codes.

The instructions work in 1996 and newer vehicles such as Buick Enclave, Lesabre, Lacrosse, Verano, Regal, Lucerne, Rendezvous, Park Avenue, Allure and Encore.

Common Buick Problems

• MAF Sensor - Mass airflow (MAF) sensors can get fouled by dirt over time, especially if performance filters are used. A dirty MAF sensor will give false readings, resulting in incorrect air-fuel mixture and engine running issues.  In most cases, dirt buildups can be easily cleaned off with a MAF cleaner fluid. Another possibility is a loose connector. Related Code: P0102

• Vacuum Leaks - Various vacuum leaks can cause engine running issues, especially noticeable on idle or low engine speeds. Tracking down leaks can sometimes be difficult and you may need to use a smoke generating machine. Related Code: P0171 - system too lean 

• Catalytic Converter - Any higher-mileage Buick will most likely have some emission control issues triggering a check engine light.  In most cases, it is either caused by a clogged catalytic converter or a faulty downstream O2 sensor. Related Codes: P0410 and P0420

• Variable Valve Timing Issue - Problems with Variable Valve Timings are quite common on a 3.6L V6 engine. In addition, to check engine light, you will experience a lack of acceleration, stalling and poor throttle response. In most cases, the problem is within the timing chain, which needs to be replaced without any delay. Related Code: P0008

• EGR Valve - EGR related problem is, in most cases, caused by a carbon buildup within an EGR valve. While this will not affect the engine performance in general, you might have a bit higher fuel consumption. If not too extreme, carbon buildup can be cleaned with EGR cleaner spray. Related Code: P0401

• Engine Coolant Temperature Sensor  - A bad coolant temperature sensor is a fairly common fault with some Buicks. It will give false temperature reading, causing rich engine operating conditions and incorrect temperature reading on your dashboard. In addition to the sensor itself, make sure the wiring is not damaged. Related Code: P0115

• Oxygen sensor - O2 sensors may fail which then triggers the check engine light to stay on and fuel efficiency to decrease. O2 sensors monitor oxygen levels in the exhaust which helps the engine control unit determine the fuel mixture. The engine control unit can determine if the fuel mixture is burning rich (less oxygen) or lean (more oxygen). 

Buick Check Engine Light Flashing

One problem that must never be ignored is a check engine light that is flashing, especially if accompanied by engine shaking and juddering.

A check engine light going on and off intermittently signals an engine misfire, which can cause damage to the catalytic converter and other engine components.

It is not recommended to drive the vehicle if the check engine light is flashing.

Conclusion

Buick check engine light or service engine soon light may come on for a number of reasons. 

The first step is to check the gas cap and tighten it. The check engine light may require a couple of days to reset on its own. An OBD-II scanner can be used if you would like to reset it as soon as you tighten the gas cap.

If the gas cap is not loose or damaged, the next step is to read the fault codes with an OBD-II scanner.

You can either take your car to the workshop for a full diagnosis or get your own scan tool. These devices come in all shapes, sizes, and prices to choose from.