The Check Engine Light is on but the scanner shows no codes.

Check engine light turned on shortly after mechanic checked alternaator and battery voltage with his tool. The mechanic told me the battery (not the IMA battery) is dead after checking the voltage. But I bought a new scanner and it shows no codes and says MIL status is off, although the check engine light is on.

My car has 140000 miles.
My car has an automatic transmission.

How to Identify and Fix Common car Problems ?

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Old Battery. Bad Spark Plugs. Loose Gas Cap or Missing Gas Cap. Fuel and air metering systems problems.
The codes can be read by bridging the two pins in the service connector and reading the MIL on the instrument cluster (all models). Vehicles 2000 onwards are fitted with a 16-pin diagnostic behind the centre console on the passenger side. A fault code reader is required to retrieve or clear codes via this connector.
2022 Honda Civic Check Engine Light Flashing

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

2009 Honda CIVIC (1.8L 4 -cyl Engine Code R18A1 R) Motor Oil, Filters and Lubricants – AMSOIL.
There are thousands of possible diagnostic codes possible, some that are specific to a manufacturer or particular vehicle, and many that are generic across all vehicles.
Codes P0300-P0399 indicate engine misfire or issues with the ignition system. Here are the descriptions of some of them: P0300: Engine misfire related to multiple cylinders. P0301: Engine misfire in cylinder 1.
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.
2008 Honda CIVIC (1.8L 4 -cyl Engine Code R18A1 R) Motor Oil, Filters and Lubricants – AMSOIL.
Check your gas cap first. Many vehicles have a loose gas cap indicator that will be triggered before your check engine light comes on. If your gas cap is loose or the seal is not tight, the vapor leakage can cause your fuel system to trigger the check engine light.
B – Means to replace engine oil and oil filter. Also inspect various systems and components (see applicable service manual for details).
Code 4 on the older Honda Civic indicate a problem with the engine crankshaft position sensor.
Will the check engine light reset itself? The check engine light on your Honda will usually shut itself off if the issue or code that caused it to turn on is fixed. For example, if the cause of your check engine light coming on was a loose gas cap, if it`s tightened, the light will turn itself off.
P0162: O2 sensor circuit malfunction (bank 2, sensor 3)
You can get a false code from the computer that shows a defective part that is actually working properly. Computer codes are only about 20% of the information we use to diagnose a check engine light.
These problems can range from faults within the electrical system, the engine, fluid levels or to problems within the car`s emissions system. The problem can even be as simple as forgetting to tighten your gas cap – in fact, this is the most common reason why check engine lights appear in the first place.
2010 Honda CIVIC (1.8L 4 -cyl Engine Code R18A1 R) Motor Oil, Filters and Lubricants – AMSOIL.
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.
This is a sign you should stop driving and have your car looked at by a mechanic as soon as possible. Use your best judgment on whether to call a tow truck or drive yourself to a nearby repair shop. Is the light flashing? In many vehicles, there are two types of check engine lights—a solid light and a flashing light.
Check your gas cap first. Many vehicles have a loose gas cap indicator that will be triggered before your check engine light comes on. If your gas cap is loose or the seal is not tight, the vapor leakage can cause your fuel system to trigger the check engine light.
This is a sign you should stop driving and have your car looked at by a mechanic as soon as possible. Use your best judgment on whether to call a tow truck or drive yourself to a nearby repair shop. Is the light flashing? In many vehicles, there are two types of check engine lights—a solid light and a flashing light.
The emissions/exhaust system is the most likely culprit for many check engine lights being illuminated. There could be an exhaust leak or a problem with the catalytic converter. The mass airflow sensor (MAF) is another sensor that is easily tripped or can fail.
Check your gas cap first. Many vehicles have a loose gas cap indicator that will be triggered before your check engine light comes on. If your gas cap is loose or the seal is not tight, the vapor leakage can cause your fuel system to trigger the check engine light.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

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.

p0011 code,check engine light one, changed bank 1 vvt solenoid and check engine light still on?
ANSWER : The P0011 code is typically caused by oil issues with the car. I would particularly make sure the engine oil level is not low. The VVT solenoid relies on proper oil levels to do their job. If they don’t have enough oil, they won’t work. You can have a mobile technician from YourMechanic visit your home or office to inspect the Check Engine Light for you. If you follow through with a repair with us you will be reimbursed for the cost of inspection.

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.

check engine light O2 sensor already replaced same codes still popping up after replacing old O2 sensor
ANSWER : Hi there. What you received from the parts store was a code retrieval, not a diagnostic. The codes are set when a fault is detected against normal operating parameter. The computer does not know what caused the fault, only that the fault meets the criteria for this code to set. There could be a problem in the wire harness, converter, or the ECM. The code and data are needed to properly assess the direction that a diagnosis needs. I strongly suggest having a qualified technician perform an inspection to avoid replacing unnecessary parts. Your Mechanic has several available technicians that can assist you with a check engine light inspection.

I have a 2007 dodge ram 1500. Check engine light was on code came up as alternator. Replaced it and the check engine light is stil
ANSWER : Hi there. When an error code is created, it is often stored in the ECU until it is cleared by a professional mechanic during a check engine light inspection. It is possible that this is the source of your error light, especially if you are not having any further problems starting your vehicle.

P2196 OBD-II Trouble Code. came and went in 24 hours. 4 starts.
ANSWER : If the mechanic tested the output (functioning) of the oxygen sensor, especially according to the protocol at this link and found that the sensor was non functioning at that time, what you might be experiencing is a "failing" oxygen sensor and so the latest instance of Code P2196 might be explained by that. A complexity though is Code P2196 has many causes other than a failing oxygen sensor including: a faulty fuel pressure regulator; MAF (Mass Air Flow) sensor; ECT(Engine Coolant Temperature) sensor or damaged ECT wiring; leaking or stuck open fuel injector or injectors; and spark plugs and/or coil pack. Basically, if the Code (P2196) recurs, the oxygen sensor output can be re-tested but the mechanic will hopefully be aware of all these other possible causes of that Code setting. If the Code recurs, you can request a check engine light diagnostic and a certified Mechanic, dispatched by YourMechanic right to your location, will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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.

Service engine warning, MAF code and O2 sensor code, along with check suspension light are turned on
ANSWER : Hello, it sounds like you have quite a few things going on. I am going to do my best to break them down for you.

First if the engine is very loud when idling and the belt has already been replaced, there may be an issue with the tensioner or idler pulley.
Next, the Navigator is known for needing service to the air suspension system as it gets up in miles, the most common causes of these are the air struts themselves have failed, or one of the air lines has a leak.
Lastly, if the O2 sensor and MAF are continually coming back after the sensors have been replaced, the most common cause would be either an exhaust leak or a vacuum leak.

Qualified technicians such as the ones at YourMechanic will be able to diagnose these issues and recommend the best path to repair, starting with a diagnosis of your warning lights.