Skip the auto shop - Our mechanics make house calls

Q: What Types of Trouble Codes Cause Lights to Come On in My Dash?

asked by on

What types of trouble codes cause lights to come on in my dash?

A: Different vehicles have a different number ...

Different vehicles have a different number of lights on the dashboard to warn you of problems, some with just a few basic lights while others have plenty to distinguish between different issues. This article will cover just the bright yellow light that says Check Engine, Service Engine Soon, or has a symbol of an engine on it. When this light comes on, it is due to a problem with one or more systems in the vehicle. This article will help you better understand the reasons the light comes on.

There is much debate who had the first Check Engine Light (CEL) to alert the driver there is a problem. There were manufacturers that started using them dating back to the late 1960’s but it was not till the year 1996 that there was a group effort by most if not all the manufacturers to standardize what is now called on board diagnostics (OBD). Since then there has been improvements to the systems to both control and monitor the operations of the engine, transmission, and other systems. The CEL does not come on for every fault in these systems but will come on for the most part when the vehicle manufacturer thinks it may harm the occupants or vehicle and is a safety hazard. It will blink or come on when the emission levels are thought to be exceeding limits imposed by the Environmental Protection Agency (EPA).

The codes that will cause the light to come on in the dash are mostly all engine or transmission trouble codes. The manufacturer may allow the light to come on for additional systems and these codes can be OBD generic or manufacturer specific related codes. There are over 3000 possible codes that are used for vehicle systems. Most codes below 1000 are generic type codes and the rest can be generic or manufacturer specific.

When the Check Engine Light comes on the operator should look for common problems like the fuel cap was left off. Open the hood and look for visual loose items like air filter inlet hoses. Your Check Engine Light is only going to alert the operator that there is a problem and a computer scan will give you a diagnostic code that can be diagnosed. The light was designed to alert you to take it to a mechanic to have it tested and diagnosed. Today’s drivers now have their own diagnostic scanners or go to parts stores where they scan your car for free and give you a code so you can search it up and replace the part that may fix the code. This is where the CEL can sometimes lead to a misdiagnosis and hurt the vehicle owner. The code is designed to help direct a mechanic to a specific pinpoint test that will isolate the fault for a correct repair. The repair does not always include replacing parts.

If you have a vehicle that has the Check Engine Light coming on, then remember that the light is letting you know that you have a problem that can do harm to one or more systems in your car or may be unsafe to operate your vehicle. You should get the light diagnosed as soon as possible to prevent being stranded or harming vehicle systems. There are other lights on the dash that may come on at the same time in some vehicles to alert you to a particular system that is having a problem. You may see lights like ABS, airbag, SRS, EPC, TRAC, TRANS, or others that will cause the Check Engine Light to come on if the engine is using that system for its controls. The engine and these other modules communicate on a network in most vehicles and the engine control module (ECM) controls the CEL through this network of modules.

The next time you see the Check Engine Light on, keep in mind the complexity of the systems involved in turning on this light and some of the possibilities and problems for damage to your vehicle systems. If you are unsure where the problem might lie, have a certified mobile mechanic from YourMechanic inspect your Check Engine Light at your home or office.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: Check engine, traction off lights are showing

The Check Engine Light is likely still on due to the oxygen sensor faults. The unfortunate thing is that engine computers sometimes cannot detect another problem if they are dealing with one already. That may be why it didn't have...

Q: Passenger side air bag light won't stay off

It does indeed sound like your problem is with the occupant weight sensor and/or its circuit. I'm assuming the recall you had performed was NHTSA 13V 069000, which involves replacing the occupant weight sensor. If the dealership hasn't been...

Q: Engine light came on suddenly

Hello. Typically when the reduced engine power light becomes a factor, the engine itself runs much slower and will lack power on acceleration. The vehicle needs to be scanned for diagnostic codes. From there the codes we already know are...

Related articles

How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.