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P0203 – What Does It Mean and How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


P0203 is an OBD-II Code that refers to Injector Circuit Malfunction – Cylinder 3


A P0203 code is a generic diagnostic trouble code that occurs when the PCM/ECM receives a signal indicating a fault in the injector circuit for cylinder 3. The computer searches for a specific range of voltage and resistance from each injector circuit.

When the results are found to be abnormal, a diagnostic trouble code (DTC) will be generated.


Common causes for this code include:

  • Problematic intake manifold (runner) tuning valve 
  • Damaged valve parts 
  • Valve is stuck 
  • Very cold conditions 
  • An issue with the wiring (e.g. chafed, cracked, corroded, etc.) 
  • Broken electrical connector 
  • ECM issue Valve contamination


The symptoms of a P0203 code are:

  • Poor fuel efficiency
  • The engine may misfire
  • Engine Running badly
  • Lean or rich conditions
  • While running, the engine dies.


To diagnose a P0203 DTC code, a technician would:

  1. Scan for codes in the ECM and look at the freeze frame data for failure.
  2. Visually inspect the wiring and connectors.
  3. Test the injector circuits for proper voltage and resistance using a scan tool or multimeter. 
  4. Check for air leaks in the intake system.
  5. Clean the throttle body and intake manifold.

Common mistakes

The following are some of the most common mistakes that a technician may make when diagnosing a P0203 code:

  • Not thoroughly inspecting all the wiring and connectors.
  • Not checking the power and ground circuits to the ECM.
  • Replacing all the injectors when only one is faulty.
  • Failing to clean the throttle body and intake manifold.

How serious is this?

A P0203 code is serious because it can cause the engine to misfire and run poorly. If not repaired, this may lead to engine damage.

What repairs can fix the code?

repair manuals

The following are solutions that may fix this problem:

  • Bad wiring, connectors, and modules repaired or replaced
  • Replacing a bad injector
  • Replacing the intake manifold (runner) tuning valve
  • Cleaning the throttle body and intake manifold

Related codes

A P0203 is related to and may be accompanied by the following codes:

P0202 – Injector Circuit Malfunction – Cylinder 2

P0204 – Injector Circuit Malfunction – Cylinder 4

P0205 – Injector Circuit Malfunction – Cylinder 5

P0206 – Injector Circuit Malfunction – Cylinder 6


In conclusion, the P0203 code is a diagnostic trouble code that refers to a problem with the injector circuit for cylinder 3. The most common causes for this code are a problem with the wiring, connectors, or modules. Other causes may include a bad injector or intake manifold (runner) tuning valve.