P0203 OBD2 Trouble Code – check your fuel injector and wiring!

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P0203 OBD2 Trouble Code


Meaning of P0203 Generic OBD2 Trouble Code

The technical definition of a P0203 fault code is: Injector Circuit Malfunction in Cylinder 3

This basically indicates the ECU is detecting a fault in the injector circuit in cylinder #3. This trouble code is observed in a wide array of import and domestic vehicles equipped with three, four, six, eight, ten, or 12-cylinder motors.

Pro Tip
If you got this P0203 OBD2 Trouble Code, start by checking the wiring and injector in cylinder #3. Don’t just replace the fuel injector! Test it! Also, bust out your digital multimeter and check the wiring because many times the issues is a bad ground or melted wires!

Upon starting the engine, the ECU will monitor the injector circuits for the proper voltage and resistance. If one of either value are out of range, the ECU will trigger a check engine light and a P0203 which can be read using your OBD2 Scan Tool. The vehicle will also enter into failsafe mode to protect the engine until the problem is rectified.

ScannerDanner did a great writeup on diagnosing a similar code P0205; which is for Injector #5 but uses similar techniques and steps to narrow down the issue. In the video he shows methods for testing fuel injectors, checking for shots to ground and lots more!

What are the causes of P0203 OBD-II code?

There are two things to check:

  1. The fuel injector in cylinder #3. In most cases, the problem can be traced directly to a bad or failing injector. Of course, the proper diagnostic procedure is to confirm the resistance of the injector. If the values are not within the proper specs, it is time to replace the fuel injector. Watch this short video on testing fuel injectors.
  2. Fault wiring or bad connection boot. If the injector is fine, the P0203 OBD2 code is most likely caused by faulty wiring or poor electrical connection. The fuel injector utilizes power to deliver the fuel. Any wiring problems will cause the injector to operate poorly, hence affecting engine performance.

P0203 fault code DTC explained

What are the symptoms of P0203 DTC?

The symptoms are hard to miss. The most common symptoms caused by this generic fault include but are not limited to:

  • Check Engine Light displayed
  • Hard starting (or a not start condition)
  • Rough idling
  • Poor acceleration
  • Engine stalling
  • Repeated misfires
  • White smoke

A dying fuel injector is a bad thing. If you have an older vehicle, consider replacing all the fuel injectors to save time and money.

diagnosing a p0203 generic fault code
The cost will depend on if it’s an issue with wiring or injectors!

How much does it cost to fix P0203 fault?

This is going to depend on where the issue is:

  1. Faulty injectors – This will cost between $1,000 and $1,500 if you take it to a shop. If you do the work yourself, it will cost you around $800-$1,000 for the injector parts.
  2. Bad wiring – This will cost from $100-$500. The biggest factor in how much it cost is how much time it takes for your mechanic to find where the wiring is damaged. Sometimes the bad wire can be found in 20 minutes, sometimes it takes hours. If you have some basic mechanic skills and a multimeter you should be able to isolate the wiring fault and save yourself a lot of $$$!

The cost of replacing the fuel injectors will depend on the make and model of your vehicle. You can expect to spend $500 to $1000 for a set of new OEM fuel injectors. If you are short on cash, you can try replacing the solitary bad injector and see how it goes. For newer cars, go straight to the dealership or service center and have the problem fixed under warranty.

But there’s some good news. If the P0203 fault code is often caused by faulty wiring or bad electrical connections, all you need are electrical tape, a wire splicing tool, and a bit of common sense to correct the issue. You will need to check the electrical sockets, connectors, and the wiring harness in the injector circuit of cylinder #3. However, the first step is to confirm injector operation in cylinder #3 before ruling out a wiring problem.

Don’t waste any time if your vehicle has a check engine light and P0203 DTC! The severity of the symptoms might render your car unusable. Continued operation or neglect can seriously lead to expensive engine damage.

Fuel injector cleaner might work to fix this code. If you’re still having trouble, you might have a faulty Fuel Pump or Fuel Pump Relay



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