I would like to know why the check engine light is on in the computer but not in my dashboard?

I tried to do the smog check but in the computer shown the check engine on but not in the dashboard

My car has 240000 miles.
My car has an automatic transmission.

Experienced mechanics share their insights in answering this question :
This may be related to a malfunction in the instrument cluster. Generally, the check engine light comes on when something fairly serious is going on with the vehicle. This can happen for many different reasons such as a faulty mass air flow sensor, a faulty O2 sensor, a bad catalytic converter, bad spark plugs or spark plug wires and many other reasons. Due to the wide range of possibilities for the check engine light to come on, the best and most efficient way to narrow down the scope of what may be causing this is to have the vehicle hooked up to a scanning tool to download any potential fault codes that may have registered in the computer. This will allow a mechanic to determine more specifically what to look for in diagnosing your vehicle. I would recommend having an expert from YourMechanic come to your location to take a look at your vehicle to determine what may be causing your check engine light to come on.

How to Identify and Fix Common car Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

Locate the battery and find the negative terminal. Disconnect the negative terminal connector and keep it away from the terminal for about 30 to 60 seconds. Reconnect the negative terminal cable and tighten everything back up. That`s it!
Jeep Grand Cherokee Check Engine Light Flashing

Other common reasons for a Check Engine Light are a malfunction with the fuel injection system, damaged oxygen sensor, dirty mass airflow sensor, faulty head gasket, faulty emissions control part, or defective spark plugs to name a few.

A loose gas cap is one of the most common reasons for the check engine light to go on. Check that your gas cap is screwed on securely and that it`s in good condition. If you have a tank of bad gas in the car, your check engine light may come on.
If the check engine light illuminates, it will either blink or remain constantly illuminated, depending on the problem. A blinking light, or in some cars a red light instead of a yellow or orange light, indicates a problem that needs immediate attention. Either way, you should have the vehicle checked by a mechanic.
If the engine light comes on solid, it may still be a reason for concern, however it doesn`t immediately need to strike fear in your heart. A solid Check Engine Light can mean something like a loose gas cap, or it can indicate a more in-depth problem like a fuel, timing, or transmission issue.
Sometimes, the check engine light comes on to let you know that there`s a problem with the car`s internal diagnostic mechanism. That means the system could be “finding” a problem that doesn`t exist, or it could be that loose wire systems are creating a false positive in the system.
A check-engine light will shut itself off if the condition that caused it is remedied. So, if your converter is marginal, and you did a lot of stop-and-go driving, which creates high demand for the converter, that might have turned on the check-engine light.
Low Oil and Check Engine Light

However, low oil pressure, which can be caused by low oil levels, can be a reason for the check engine light to turn on. Low oil pressure can seriously interfere with your car`s performance and disable your vehicle if not addressed immediately.

A misfire typically occurs when the timing of this ignition is off. Jeep Grand Cherokee P0300 indicates that two or more cylinders are experiencing misfires.
A check engine light will shut itself off if the condition that caused it is remedied. So, if your converter is marginal, and you did a lot of stop-and-go driving, which creates high demand for the converter, that may have turned on the check engine light.
A check engine light will shut itself off if the condition that caused it is remedied. So, if your converter is marginal, and you did a lot of stop-and-go driving, which creates high demand for the converter, that may have turned on the check engine light.
No reset is required. Most of the time, there`s a problem when the check engine light is on.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Traction light/reduced engine power and check engine light coming on
ANSWER : Hello. From what you describe, it would appear that your vehicle may be experiencing some sort of intermittent wiring or sensor issue. If the problem occurred again after driving over a bump, then it may be possible that a damaged or loose wire is shorting or having contact issues. A common issue that can cause stalling is a faulty crank position sensor or wiring. I would carefully examine the engine for any loose or damaged wires. If the Check Engine Light comes back on, I would recommend having the trouble codes scanned before resetting the computer.

Abs light, emergency brake light, steering wheel assist light, engine light, EPC light, traction control light
ANSWER : Hello, thank you for writing in. The vehicle does utilize a lot of the same sensors for these systems. Are there any other codes that are coming up when this code appears? If so you will want to take these into consideration when processing the repair and making a diagnosis. The module may be bad, and replacing it should fix the problem. The lights should turn off once the main computer recognizes the new module and the sensors sync up. If you believe the sensors need to be cleaned you may do so. Do as minimal as possible to make sure you are not damaging the sensor or disrupting the wiring inside. A bad connection would make the lights stay on. With so many lights that are effected by the module being illuminated, the module is likely bad or does not have a connection. Check the connection first and then resort to replacing the unit. For more help with these electrical tests, contact our service department.

Check Engine light on. Would the computer give all error codes in one shot? How do we know the engine’s condition?
ANSWER : Hi there. From the description you have provided, I’m am inclined to agree with your assessment of a used engine being installed in your vehicle. An inspection of the engine, by a qualified technician could determine whether the engine is sound. The Check Engine Light on and having a TPS (throttle position sensor) code does not necessarily mean the sensor is at fault. Circuit tests should be performed to confirm the fault. The likelihood of the ECM (electronic control module/computer) giving you all the codes at once is remote. Other component failures could occur. Address those as they come up. Even though you already made the purchase, I recommend having your vehicle inspected by a certified technician so that you can get a thorough evaluation of the car’s true condition.

My car shows the Check Engine Light and DPF lights and coil light on the dashboard. What action should I take?
ANSWER : Hi. The EGR valve needs to be replaced and the passages to the EGR need to be cleaned. The EGR location is very tricky to get to so you may need a professional technician (such as one from YourMechanic) who can complete this repair. The diesel particulate filter (DPF) filter should also be replaced and the housing for the filter should be inspected for damage due to the people stealing your filter.

I would like to know why the check engine light is on in the computer but not in my dashboard?
ANSWER : This may be related to a malfunction in the instrument cluster. Generally, the check engine light comes on when something fairly serious is going on with the vehicle. This can happen for many different reasons such as a faulty mass air flow sensor, a faulty O2 sensor, a bad catalytic converter, bad spark plugs or spark plug wires and many other reasons. Due to the wide range of possibilities for the check engine light to come on, the best and most efficient way to narrow down the scope of what may be causing this is to have the vehicle hooked up to a scanning tool to download any potential fault codes that may have registered in the computer. This will allow a mechanic to determine more specifically what to look for in diagnosing your vehicle. I would recommend having an expert from YourMechanic come to your location to take a look at your vehicle to determine what may be causing your check engine light to come on.

While driving on freeway truck goes into a limp mode, and the check engine light, abs light, parking break light, service brake
ANSWER : It is possible that you could be having an issue with your powertrain control module. This is somewhat of a common problem on many GM vehicles. I would recommend having your vehicle inspected by the dealership to determine if the powertrain control module is functioning properly. If not, a reflash of the powertrain control module may resolve the issue but often times it must be replaced.

2006 Ford Mustang has check engine light on
ANSWER : There are countless potential causes for your illuminated check engine light. The mechanic manually turned off the light, but it came back on because the problem has not been fixed. The first place to start is retrieval of the stored diagnostic trouble codes (DTCs). These codes serve as a starting point for any further diagnostics a mechanic may perform. Codes will be stored anytime the check engine light is on. Since the first mechanic was unable to fix your concern, I recommend giving the professionals at YourMechanic a call. We offer expert check engine light diagnosis and repair.

Check engine light refuses to go off after engine replaced
ANSWER : Hello there, you have a long series of issues going on with your 2013 Hyundai Sonata. If you keep getting a repeating oil light on than there is likely a fault in that system.

Since this fault has lasted after the engine was replaced it could be a oil pressure sensor, wiring harness fault, ECU fault, oil pump, oil strainer clogged, or low oil pressure.

To diagnose this issue properly you need a complete vehicle inspection to start from square one and identify the root cause of all this.