Check Engine Light On When Car is Off | Causes & Solutions
Seeing your check engine light on when the car is off could indicate a number of different things such as loose gas cap, battery problems, and electrical glitches.
You might see the check engine light turn off only within a few seconds after turning the car on, or it may stay on for a long period.
Regardless of how long you see the check engine light stay on, you need to check out the problem and make sure that you know exactly what is causing the check engine light to flash.
Common Reasons Why Check Engine Light On When Car is Off
Check engine light is triggered by a computerized system alert. This alert means there’s a problem with the engine or the emission system.
Occasional flashes of the check engine light may indicate temporary engine issues, while longer signals may mean a misfiring of the engine, emission problems, loose gas cap, and so on.
Below are some common situations you will face when you see the MIL has activated when the engine is off power.
Ignition Key on Without Starting the Engine
If you have an old car, a common reason why the check engine light might turn on while the engine is off is a delay between the ignition and engine triggers.
In such old car models, turning the ignition key on without starting the engine can trigger the alert on the check engine light.
This happens because the ignition starts to create a current flow that cannot pass through a closed engine loop. The excess energy has nowhere to go, so it builds up, overheats, and damages the coils.
This signals off the alert on the check engine light.
Loose Gas Cap
One of the most common reasons is a loose gas cap.
If the gas cap is not airtight, the pressure of the fuel container will drop and this will create an alert code in the ECU.
Battery Problems
A faulty battery might trigger the check engine light to turn on when the engine is still cold. The simple reason for this is a draining battery.
The check engine light is controlled by your car’s computer or Electronic Control Units (ECUs) system.
If the ECU is fizzling out due to lack of battery power, then the check engine light will come on, regardless of activated engine power, to indicate that you should get your car serviced or the battery recharged/replaced.
Faulty Oxygen Sensor Issues
The check engine light will alert you if the car has a faulty oxygen sensor. A faulty oxygen sensor will not be able to accurately assess the amount of oxygen present in the exhaust gases.
So you run the risk of engine misfires, low levels of emission, fuel wastage among other problems on the go.
Try to restore the oxygen sensor as soon as possible. When the oxygen volume is adequate, and the ECU has received a signal for the presence of optimal oxygen levels, your check engine light will turn off.
Wiring Problems
There is an intricate threading of wires in your car’s electrical system. If these wires are molten, damaged, loose, or worn out then there might be a short circuit causing a drop in voltage which will be picked up by the ECU.
Additionally, a short circuit will drain out the battery, leaving the engine incapable of being turned on.
So, if you have failed to power up your engine, but you can see the check engine light has lit up, check the wires or contact a mechanic to do this task.
Temporary Electrical Glitches and Residual Codes
A temporary electrical glitch or a software mishap can cause the check engine light to stay on for a few seconds.
If you see the check engine light on for just a few seconds, then it might be a temporary connection problem of software in the systems onboard.
Another reason for the check engine light to flash can be residual codes. These flashes are also very short-lived, and they are a result of your car’s ECU memory.
If a problem has been fixed very recently, the MIL takes some time to update its signal codes. As a result, the check engine light turns on as per usual.
After completing a drive cycle of 60 miles, the previous fault-recording code will be overrun by the new memory of a functional code and result in a relaxed ECU system that doesn’t turn on the check engine light in the alert.
Frequently Asked Questions [FAQs]
How long does it take for the check engine light to turn off after an issue has been fixed?
It takes about 10 to 20 cycles for the check engine light to clear off after an issue has been fixed.
Keep repeating the drive cycles to erase residual error codes and override the ECU memory with new codes.
What is meant by 1 cycle of drive?
One drive cycle refers to the completion of a single occurrence that starts when a car is first turned on, driven for a few miles, and finishes when the car is turned off.
How long should a single drive cycle last?
Typically, a single drive cycle should last 30 minutes in total, with 10 minutes for ignition and power off, and 20 minutes of being on the move.
What to do if I see an occasional blinking of the check engine light in my car?
Get a preliminary discussion with your mechanic if you see the check engine light blinking 1-2 times.
If the problem disappears after a few drive cycles, then it was some minor issue and if the problem persists there is a more serious underlying issue.
What are some regular practices that can help me to maintain the health of my car’s engine?
Besides routinely sending your car for maintenance services, change your fuel filter, air filter, and engine oil after every 5000 miles traveled.
Conclusion
We can conclude by saying that if you see your check engine light on when the car is off, then there is nothing casual about it.
As we have seen, such an alert system as the check engine light is designed to note and alert you about problems regarding fuel and emissions.
If you see the check engine light blink a few too many times before starting your car then you should consult a qualified mechanic for a proper diagnosis.
This is why you must treat this particular problem with the highest priority. A bit of delay now can cause a much larger problem for both your car and your bank balances in the near future.
Link:
