12 Reasons Why Your Mitsubishi Check Engine Light is On
The Check Engine light show up on the dash in your Mitsubishi? Unnerving, isn't it? With less shorthand of a name like malfunction indicator light, or MIL, it makes sense. Not only does the warning mean a damper put on a daily commute, or a weekend getaway postponed. It can tell you that you've got a serious problem with, say, the engine or transmission.
Sure: sometimes, the reasons why it's suddenly lit up aren't anything to spend much time or energy worrying about. More often than not though, some kind of maintenance is going to end up needing to be done. Let even the small stuff go, though, and it can still mean the car, truck, or SUV you love stuck in the service bay at a Mitsubishi dealer, running up quite a bill.
Good thing you came to us to figure out exactly what's going on; we've got more than a few explanations. Here's everything you need to know -- how to diagnose a Check Engine light, and more importantly, how to deal with what ends up being the trouble.
12 Causes of a Mitsubishi Check Engine Light Coming On
1. Dirty or Damaged Oxygen Sensors
Oxygen sensors figure out whether the air levels in your exhaust are right; in doing so, they help the engine tell how much fuel it should burn. Your Mitsubishi may have anywhere from two to four: usually, one per exhaust manifold. There might even be one just after the catalytic converter.
At any rate, they're often made to last anywhere from 50,000 to 100,000 miles; however, one can fail just because your motor oil or fuel has gotten it dirty. If you have to replace any, all you have to do is unscrew the old oxygen sensor most of the time, and then screw in the new one. Still having trouble after that? Check your vacuum hose; you may just have to reconnect it.
2. A Faulty Mass Airflow (MAF) Sensor
Mass airflow sensors measure how much air enters the engine and sends that info to the engine control unit (ECU, or engine computer), which uses the data to determine how much fuel to burn. If the engine in your Mitsubishi is idling roughly, hesitating, stalling, or otherwise not running right, MAF sensor failure is probably the culprit. If it needs replacement, you can find it either near the engine air filter or on the filter's box.
3. A Bad Car Thermostat
The thermostat in your Mitsubishi helps manage the valve that opens and closes to release coolant into its cooling system. If the temperature gauge in your dash reads dead-center or slightly cold, it's working fine. If the engine and AC and heating systems aren't running right, though; if some hoses and gaskets are warped; if the valve's stuck; and if coolant's not moving through things like the radiator the way it's supposed to, then the thermostat's likely broken down.
4. Defective Ignition Coils
Ignition coils help a Mitsubishi ignition create electricity, so the spark plugs can capture its charge and use it to ignite the fuel and air mixture in the engine. So, it makes sense that their failure's usually caused by bad spark plugs or wiring, if not engine heat, vibrations, an overly rich fuel-to-oxygen ratio, or an overly poor ratio. Have trouble starting your vehicle, and one that no longer works may be to blame.
5. Catalytic Converter Problems
The engine in your Mitsubishi burning air and gas for power produces noxious fumes such as carbon monoxide, hydrocarbons, and nitrogen oxides. Your exhaust system helps remove them safely, protecting you, your passengers, and the environment. It couldn't do that, though, without a catalytic converter -- cat, for short.
it contains a metal catalyst coating -- often, a combo of platinum, rhodium, and palladium -- which captures and contains most pollutants, converting them into water vapor and carbon dioxide. If your engine's slower and less responsive, you're having problems accelerating, there's excessive, black smoke coming out of the exhaust pipe, you smell something sulfuric, like rotten eggs, and there's excessive heat coming from under your vehicle, cat failure's the likely cause.
6. A Fuel Injector Malfunction
Part of the fuel system in your Mitsubishi (along with a fuel pump, fuel tank, and fuel lines), fuel injectors do the same thing carburetors did in older vehicles, but more efficiently, with fewer emissions. That is, they spray gas through nozzles into your engine cylinders at the proper pressure, using electronically controlled valves designed to open and close at the right times.
Factor in help from an engine control unit and sensors, which figure out when the injectors should spray, and the engine can get the right ratio of fuel to oxygen. Its internal combustion process can then happen right, and your engine can start running on its own power. Clogs or leaks, however, tell you that the system's having a tougher time getting gas where it needs to go; failed injectors may be the issue.
7. A Blown Head Gasket
A seal located between the two main parts of your engine -- its core or block, and the cylinder head -- the head gasket is one of the most important parts of any motor. It encloses the cylinders and both helps them maintain firing pressure and prevents coolant and motor oil from leaking. It fails, and your engine will overheat. It does so repeatedly, and it'll end up damaged, making for one seriously expensive repair.
So, keep an eye out for the signs of a bad one. They include white exhaust smoke, a bubbly radiator and coolant reservoir, the motor oil turning white, oil and/or coolant leaking from the gasket, low coolant levels without an apparent leak, and loss of engine power. See any, and you should shut down your engine; don't try to release any pressure from the gasket. Do a cooling system test to rule out other issues, and then get the gasket replaced ASAP. It's usually a complicated job best left to a certified mechanic.
8. An Emission Control System Issue
Sometimes, a Malfunction Indicator turning on is just a case of, say, a defective evaporative emissions (EVAP) canister purge control valve. A failed emissions test, worsening fuel efficiency, trouble starting, a vacuum leak, and general engine trouble make it the most likely offender.
9. The Powertrain Control Module (PCM) Needs Reprogramming
The PCM in your Mitsubishi controls, among other parts and systems, its engine and transmission. Your ride wont start, engine performance isn't what it used to be, you've got other warning lights on the dash, and emissions can't be managed for whatever reason, and it's probably faulty. Reprogramming ("flashing" or "reflashing") usually calls for special tools and a trip to a dealer.
10. Worn-Out Spark Plugs
Spark plugs are crucial to helping to get your engine running. The engine starts misfiring or failing, though; the plugs' leads seem to have widened or corroded; or the plugs themselves stop conducting electricity as well (or at all), then most likely, they've gone bad. Broken spark plugs usually cause catastrophic damage, too, to an engine's cylinders specifically -- and that can mean thousands of dollars in maintenance costs.
We suggest changing them sooner rather than later, before the worst happens. Your options range from basic copper to higher-performance platinum or iridium, and these days, both kinds get built to last, for millions of ignitions and up to 100,000 miles.
11. A Loose Gas Cap
If the gas cap in your Mitsubishi won't tighten or click in place; if its casing or threading gets damaged; or even if only the spring's broken, there's no real fixing it -- you'll need a replacement. Otherwise, fuel vapors from the gas tank can escape and trigger emissions system errors, not to mention that dirt can get into the tank and fuel injectors, causing issues with your vehicle running and wearing both out over time.
12. Humidity Changes
In this case, technically, nothing's actually wrong; the light just come on when, say, the seasons take a turn. Just be sure to rule out all else before, say, just resetting the MIL.
In any such cases, though, what to do is straightforward. You'll need to run an inspection: plug in a code reader or an advanced scan tool and check the error codes it feeds back. Then, working with your owner's manual's troubleshooting and other sections, you'll need to determine what parts need replacement. Not sure what to do? You're welcome to schedule an appointment at a Mitsubishi service center. In the meantime, check out a basic how-to on maintenance and then take a look at your manual's schedules for more details on what needs to happen and when.
Whatever the repairs, use OEM parts for them. For one, they'll be top-quality, as only Mitsubishi can deliver. Secondly, they'll come with a fitment guarantee, not to mention that they'll work right the first time. Third, they'll include manufacturer warranties. Fourth, they won't void your factory warranty and put you on the hook for fixes otherwise covered by it, like some aftermarket parts can.
Once you figure out your Check Engine light situation and take care of any recommended repairs, you and your Mitsubishi can look forward to getting back on the road in no time!