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Generic gasoline powertrain DTC / Fuel injector circuits

P0204: Injector circuit/open (Cylinder 4)

The controller detected a fault in the fuel-injector circuit associated with cylinder 4.

Generic definition
P0203
P0304

Likely cause paths · unconfirmed

A possible injector wiring or control-circuit fault

The code names a cylinder circuit; a connector, harness, driver, or injector winding may be involved.

  • Do not infer cylinder location without the engine-specific information.
  • Record companion circuit and misfire codes.

A possible cylinder fuel or combustion issue

An injector flow issue or another cylinder condition can overlap with an injector-circuit report.

  • Note idle and load behavior without deliberately reproducing a severe misfire.
  • Save scan data before clearing codes.

Likely causes and repair directions are general, conditional orientation. The SAE citation supports the generic DTC definition only; it does not validate these causes, tests, repairs, or fitment to a particular vehicle.

Conditional likely repairs

A code describes a monitored condition; it does not prove a failed part. Use these directions only after confirming the cause.

If confirmed: A possible injector wiring or control-circuit fault

If circuit testing confirms an open, short, connection, or driver fault, repair the isolated circuit using the OEM procedure.

Evidence to confirm

  • Electrical tests isolate the fault to a circuit component.
  • Command and monitor checks pass after repair.

If confirmed: A possible cylinder fuel or combustion issue

If injector or cylinder testing confirms a fuel-delivery fault, service the verified cause and recheck cylinder contribution.

Evidence to confirm

  • The OEM-approved balance or contribution test confirms the fault.
  • The cylinder operates normally after the confirmed repair.

Guided evidence checks

  1. 01

    Record what happened

    Note when the warning appeared, what the vehicle was doing, and any recent service or change. Do not deliberately recreate an unsafe symptom.

  2. 02

    Make only a safe visual check

    Record roughness, warning behavior, and recent engine work. Do not disconnect injector plugs or open fuel lines.

  3. 03

    Preserve scan-tool evidence

    Qualified technician

    Save all current/pending codes, freeze-frame, and available cylinder contribution or circuit data.

  4. 04

    Confirm the system path

    Qualified technician

    A qualified technician should test the injector circuit and verify injector command, wiring, and cylinder contribution with OEM procedures.

Code-specific symptom note

  • Code-specific symptoms are not verified by the cited definition. Record the driver’s actual observations separately.

This generic code reference is not an OEM procedure, does not confirm that a DTC applies to a particular make/model/engine, and is not a repair diagnosis. Follow vehicle-specific service information or consult a qualified technician.