Fuel and air

P0203 — Cylinder 3 Fuel Injector Circuit Malfunction

Severity: medium Drive with care, to a shop

What P0203 means

The engine control module fires each injector by switching its circuit to ground with a driver, and it monitors current and voltage in that circuit. P0203 sets when the cylinder 3 injector circuit shows an open, a short or readings outside the expected range. As a result, that cylinder may get the wrong amount of fuel or none at all.

Symptoms

  • Check Engine light on
  • Rough idle or vibration
  • Misfire on cylinder 3
  • Poor acceleration and reduced power
  • Worse fuel economy
  • P0303 often set along with it
  • Hard starting
  • Fuel smell from the exhaust

Possible causes

  1. Failed cylinder 3 fuel injector (open or shorted coil, sticking)
  2. Open or shorted wiring in the injector harness
  3. Corroded or loose injector connector
  4. Harness damaged by rubbing or heat
  5. Failed injector driver inside the ECM (rare)

How to diagnose

  1. Scan all codes and freeze frame data, and look for P0303 or other injector codes
  2. Inspect the cylinder 3 injector connector and harness for corrosion, chafing, melting or a poor latch
  3. Measure injector coil resistance and compare it with spec and with the neighboring injectors
  4. Check for power and injector pulses at the connector using a noid light or scope
  5. Test the wires from the injector connector to the ECM for opens and shorts to ground or voltage
  6. Swap the injector with another cylinder and see whether the code follows
  7. Check fuel pressure and fuel trim values
  8. If wiring and injector test good, check ECM power and grounds, then the ECM itself

Common fixes

  • Replace the cylinder 3 fuel injector
  • Repair the wiring or replace the connector in the injector circuit
  • Clean the terminals and restore a secure connector fit
  • Replace or reprogram the ECM if a driver fault is confirmed

P0203 on different brands

Ford · manuals
On 2024-2025 Ford gasoline engines you may see the extended code P0203:92, meaning cylinder 3 injector circuit range/performance; it describes the condition the monitor detected, not a confirmed failed part.

Questions and answers

What does P0203 mean?

It is an electrical fault in the cylinder 3 fuel injector circuit. The engine computer sees an open, a short or an out-of-range signal on the injector control circuit.

Can I drive with a P0203 code?

Only briefly and over a short distance. The cylinder isn't running properly, and unburned fuel can damage the catalytic converter, so don't put off the repair.

Do I always need a new injector for P0203?

No. The cause is often the connector or wiring, so inspect the harness, test the injector's resistance and check the circuit before buying a part.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.