By YOUCANIC on Feb 27, 2019
In this guide, you will learn what Subaru Check Engine Light (CEL) means. Common causes that trigger it to come on.
Why your Subaru check engine light plus lights such as Brake and Cruise Control (CC) come on at the same time. You will also learn how to diagnose Subaru CEL yourself.
When a Subaru On-Board Diagnostic (OBD) detects a problem that is engine or emission control related, it triggers the check engine light to come on. The OBD system then stores a fault code (also known as Diagnostic Trouble Code or DTC) in the memory. You can use an OBD2 scanner to read the code.
In many cases, Subaru CEL is accompanied by a flashing ‘Cruise Control - CC’ or ‘Vehicle Dynamics Control’. It doesn't mean that there is a problem with these systems. It simply means that they are disabled due to the engine problem.
The next step in the diagnostic process is to read the codes via the OBD-II port. You can perform this procedure yourself, see instructions below.
Subaru check engine can be caused by a number of problems. It can be something as simple as loose fuel tank cap to a clogged catalytic converter.
When you notice the ‘check engine’ light is on, the first thing to do is to observe if there are any other symptoms, such as:
If your Subaru has any of these symptoms it indicates that it is not running as it should. To prevent additional damage, start looking for a good place to safely pull over and turn the engine off.
The first thing you should when your Subaru check engine light comes on is to tighten the gas cap. You should continue driving only if there are no other symptoms.
If the gas cap is not on tight, it could allow vapor from the fuel tank to escape which triggers the check engine light. If your Subaru check engine light doesn't turn off after a few days, the next step would be to read the fault codes via the OBD-II port under the dashboard.
Replace the gas cap if the seal shows cracks.
Your dealer, mechanic or you should read the codes stored in the On-Board Diagnostic system. This is a simple procedure but requires an OBD-II Scanner.
The code may not be enough to pinpoint the cause. Do not replace parts based on the code alone.
Auto part stores such as Autozone, Advance Auto Parts and PepBoys read fault codes free of charge.
Common causes that trigger Subaru check engine light are:
The following problems seem to affect primarily Subaru vehicles such as: Forester, Impreza, Outback, Ascent, Legacy, WRX, Crosstrek.
Many newer Subarus might have a ‘check engine’ light on and ‘cruise’ light flashing after a battery change. In most cases, this is caused by a blown fuse in the engine compartment fuse box.
Other possible causes include faulty Engine Control Unit (ECU), prolonged oil changes, corroded wire harness, software issues, thermostat, cracked head, spark plug wires,
If the check engine light is flashing it means a misfire has been detected. Driving a Subaru with a flashing check engine light can cause serious damage to the engine and catalytic converter.
Flashing check engine light is one thing that you should not ignore. While this is not that damaging if you drive for a few minutes, it will have a devastating effect on your engine and catalytic converter if ignored for a long time.
You may have been told to disconnect the battery negative terminal for a few minutes to turn off Subaru check engine light. While this procedure will turn off your Subaru check engine light it is not recommended because it clears codes that would be helpful for diagnostics purposes.
Also keep in mind that if the problem hasn't been fixed, your Subaru check engine light will come back on.
You will not be able to pass a state emission test if you recently disconnected the battery or cleared the codes with an OBD2 scanner. Fix the underlying problem then drive the car for a few days before you take your Subaru for a smog test.
On some Subaru models such as the Forest, you will notice that the Cruise Control (CC) comes on in addition to the check engine light. This is to let you know that the cruise control is disabled due to the engine malfunction. Other lights such as the traction control light and ABS may also come on.
Once the check engine light problem and been fixed these lights should turn off.
Older Subarus have a green connector under the dash that is meant to be disconnected. Connecting it will send the car into a so-called ‘test mode’. A ‘check engine’ light will be flashing rapidly but no codes will be stored. In addition, engine cooling fans will be turning of and on.
Newer Subarus don’t have this connector. Instead, there is an empty fuse slot in the engine compartment. ‘Test mode’ is activated by installing a fuse is installed into this slot.
Whenever there is an engine related problem, additional systems such as Cruise control and Vehicle Dynamics Control will be deactivated. This is done system avoid additional driveability problems, as well as to gain driver’s attention. Your Subaru is designed to deactivate these systems to As long as there are no other issues, or the ‘check engine’ light is not blinking, you can drive your car. But have the problem fixed as soon as possible.
In cold weather, you could have a ‘check engine’ light that is accompanied with a misfire, rough running and splutter until the engine warms up. In this case, you might have a shrunken intake manifold gasket. This causes intake leaks and unmetered air, resulting in all sorts of driveability issues.
If your engine develops a misfire, you will be warned by a flashing ‘check engine’ and a flashing ’brake’ light. The main purpose of these multiple flashing lights is to catch your attention, as the misfire can cause damage to the engine or the emission control system in a short time.
While it is possible to reset Subaru check engine light by disconnecting the battery, this does not fix the problem. If the underlying problem is not fixed the light will come back on. Depending on the problem it could come back as soon as you restart the car or a week latter.