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P0203 OBD-II Trouble Code: Injector Circuit Malfunction - Cylinder 3

Check Engine Light

P0203 code definition

P0203 is a general OBD2 code that points to a fault in the injector circuit.

  • Note: This code is similar to P0200, P0201, P0202, or P0204-P0212. Misfire codes and rich / lean codes may be seen in addition to P0203.

What the P0203 code means

The P0203 is a diagnostic trouble code that is set when the engine control module (ECM) has detected a fault in the injector circuit for cylinder 3. The ECM looks for a specific range of voltage and resistance from each injector circuit and when the results are found to be out-of-range, a diagnostic trouble code (DTC) will be set.

Once the DTC is set, the car will enable a failsafe mode which prevents further damage to the vehicle. When a failsafe mode is set, it will remain until normal operation is detected or is repaired.

What causes the P0203 code?

  • An ECM that is faulty
  • Injector failing or failed in cylinder 3
  • Open or short found in the wiring harness
  • Electrical connection that is poor

What are the symptoms of the P0203 code?

Symptoms vary from vehicle to vehicle but the constant is the Check Engine Light being illuminated once the fault is found. Other symptoms that may occur include:

  • Poor fuel mileage
  • Running poorly
  • Engine dying while running
  • Lean or rich conditions
  • Engine misfires

How does a mechanic diagnose the P0203 code?

In all cases, the first step will be to check what codes present in the vehicle. A qualified technician will begin by installing an advanced scan tool and seeing what codes are found. Once the codes are found, the freeze frame data will be checked for what the vehicle was doing when the code was set. All codes will be cleared and taken for a test drive to verify the fault. When the fault is verified, a visual inspection will be performed on the injector circuit and the injector to look for any damage.

Next, the voltage will be checked at the injector itself. The scan tool will then be used to monitor injector operation. If all of this passes, a noid light will be installed into the wiring of the cylinder 3 injector to check for the proper voltage pulse.

Lastly, the ECM will be tested according to the manufacturer's specifications.

Common mistakes when diagnosing the P0203 code

Commonly, mistakes are made when steps are not followed or entire systems are not tested. To avoid wasting time and money only to not fix the fault, all steps should be followed in the proper order. Usually the injector is the cause for P0203, but it must be tested before it is replaced.

How serious is the P0203 code?

With P0203, if the vehicle is running poorly and is having trouble staying running, then this is a serious condition which calls for the vehicle not to be driven, and the code to be repaired as soon as possible. In much less serious cases, the only felt symptom is the Check Engine Light being turned on.

What repairs can fix the P0203 code?

Additional comments for consideration regarding the P0203 code

Specialty tools may be needed to properly diagnose P0203, such as an advanced scan tool. These advanced scan tools let technicians view much more information than just the code, such as live action data and the ability to view injector operation data.

Another tool that may be needed is a noid light set. These are tools that give the technician more data than just if voltage is present. When diagnosing injectors, an important aspect is the pulse of voltage that operates the injector. Noid lights are used to determine proper pulse time.

Need help with a P0203 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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