P0203 is a common OBD2 trouble code. It means the third cylinder in the firing order has a fuel injector that is malfunctioning. It’s generic code, which means that it means the same thing for the Toyota Sequoia as it would for any other vehicle.
When the PCM sees that the voltage from cylinder 3 is outside the normal operating range, P0203 will be thrown. P0203 is usually caused by a bad fuel injector or wiring issue. If the misfire were in cylinder 2, you’d get P0202.
P0203 is usually caused by a bad fuel injector or wiring issue.
Sequoia: P0203 Symptoms
This code is usually accompanied by noticeable symptoms. Here are the most common ones:
- Misfire– If your Sequoia’s fuel injector is not getting the right amount of fuel into cylinder three, it’ll misfire. A misfire will hurt the acceleration of the vehicle and cause fuel mileage to suffer.
- Service Engine Light– The check engine light will obviously be on, but you may or may not get a flashing check engine light as well.
P0203 Causes: Toyota Sequoia
The good news when diagnosing P0203 in your Sequoia is that you only need to look at the fuel injector in cylinder three, since the computer has pinpointed the location of the problem for you.
1. Bad Fuel Injector
Bad fuel injectors are the most common reason that P0203 is thrown by the PCM. You still want to take a look at the wiring harness. You’ll also want to test the injector. There’s a YouTube video directly above that shows how to do that. A new fuel injector is relatively affordable.
Fuel injectors can make your Sequoia’s PCM throw P0203 if they are plugged, dirty, or defective.
2. Wiring Issue
When diagnosing P0203, taking a look at the wiring around the injector is a great place to start. You want to make sure that it doesn’t look visibly damaged.
Make sure that the voltage at the injector matches the injectors that aren’t getting the code. If they aren’t that’s a good indication that something is wrong with the wiring harness.
3. Bad PCM
This is the last place that you’d want to look, but a bad PCM can be the reason why your Sequoia is getting P0203.
Conclusion: P0203 Toyota Sequoia
It’s usually not too hard to track down P0203, thanks to the fact that it is specific to the first cylinder. If there is anything you would like to add that could help the next person with their Sequoia, please leave a comment. Good luck!