P0204: Cylinder 4 Injector A Circuit/Open

What it means

The PCM detected an open or electrical fault in the cylinder 4 injector A circuit. The code does not establish that the ECU disables the injector or that a misfire code will also set.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The PCM switches the cylinder 4 injector's electrical circuit to meter fuel into that cylinder. P0204 means it detected an open or other electrical fault in the cylinder 4 injector A circuit; the code does not prove the injector has stopped operating or that a misfire code will accompany it.

Common causes

Most likely first.

1. Injector winding failed open
2. Wiring or connector fault

Symptoms

• Check-engine light
• Rough running or engine misfire
• Reduced engine power
• Hard starting or stalling

How to diagnose it

1. Record freeze-frame data and scan for cylinder 4 misfire or related circuit codes to identify the conditions present when the fault set.
2. Locate cylinder 4 using the vehicle's cylinder identification information, then inspect its injector connector and wiring for loose fit, corrosion, chafing, or heat damage.
3. Check the cylinder 4 injector connector and compare its winding resistance with the manufacturer's specification.
4. Use the wiring diagram to test the cylinder 4 injector supply and control wire for continuity and shorts.
5. If the cylinder 4 injector and its wiring pass, have the PCM's cylinder 4 injector driver checked.

Common fixes

• Reconnect or clean the cylinder 4 injector connector.
• Repair damaged wiring in the cylinder 4 injector circuit.
• Replace the cylinder 4 injector if its winding is confirmed electrically faulty.
• Repair or replace the PCM if testing confirms a failed cylinder 4 injector driver.

Can I keep driving?

Avoid driving if the engine runs rough, misfires, stalls, or loses power because those conditions can worsen and raise emissions. If it runs normally, limit use and arrange diagnosis soon.