P0204: Cylinder 4 Injector Circuit

What this code means

P0204 may mean the PCM is seeing a possible electrical or performance problem in the cylinder 4 fuel injector control circuit.

What the vehicle may do

The engine may run rough or misfire.
The engine may have a rough idle.
The vehicle may have a no-start condition.
The concern can be intermittent if wiring or connector contact changes with heat or movement.

Possible fault areas

Possible injector control or return circuit wiring concern.
Possible injector connector or terminal concern.
Possible fuel injector concern.
Possible PCM driver-side concern.

Diagnostic path

Opening Context

On this 2015-2025 F-150 with the 2.7 EcoBoost, P0204 points us toward the cylinder 4 fuel injector control circuit. In plain language, the PCM may not be seeing the injector circuit behave the way it expects. The truck may run rough, miss, have a no-start condition, or the concern may only show up intermittently. Broadly, this can involve the injector circuit wiring, the injector itself, or, less often, the PCM side of the driver circuit. Before applying power or chasing the wrong leg of the circuit, remember this warning: do not apply battery voltage across the fuel injector circuits. Permanent injector damage can result.

Start With Code Confirmation And Injector PIDs

Start with the basic system checks, then check for DTCs. If P0204 is present, continue into this injector circuit path. If the code is not present but the symptom is a no-start, rough idle, or misfire, this same path still applies. For other symptom paths, do not force this test—check what the symptom is telling you first. Next, turn the ignition ON and look at the PCM fuel injector fault PIDs, including the individual injector fault PIDs and the INJ_F mode PID. If the injector fault PID shows a concern, move straight to the harness wiggle test. If it does not show a concern, use the power balance direction next.

Use Power Balance To Separate An Active Fault From A Symptom

Before leaning on the injector test result, make sure the low pressure fuel system is operating correctly. Then carry out the Power Balance Test using the scan tool’s procedure. If that test is not available on the vehicle, continue to the next step rather than stopping the diagnosis. If the power balance result is satisfactory, the system is operating correctly at that time and the next move is symptom-based diagnosis. If the result is not satisfactory, continue to the harness wiggle test.

Wiggle Test The Injector Harness Before Pin Testing

Now run the engine and let it reach normal operating temperature. Monitor the same fuel injector fault PIDs while you wiggle, shake, and bend small sections of the harness. Work from the suspected injector back toward the PCM. If the INJ_F PID shows the concern while you move the harness, repair the wiring or connection as needed, clear the PCM DTCs, and repeat the self-test. If the PID does not show a concern, go into the circuit checks.

Check The Injector Circuits For Opens And Shorts

With the ignition OFF, disconnect the direct fuel injection fuel injector connector and the PCM connector. This test set covers multiple injectors, so only measure the circuits that apply to cylinder 4 and the component being diagnosed. If you cannot positively identify the correct cylinder 4 injector connector and circuits, pause and do not guess. For the open-circuit check, resistance must be less than 5 Ω. If it is not less than 5 Ω, repair the open circuit, clear the PCM DTCs, and repeat the self-test. If it passes, keep going. Next, still with the ignition OFF, check the injector control and return circuits for a short to ground. The resistance must be greater than 10000 Ω. If it is not greater than 10000 Ω, repair the short circuit, clear the PCM DTCs, and repeat the self-test. If that passes, turn the ignition ON and check the same circuit set for a short to voltage. If any voltage is present, repair the short circuit, clear the PCM DTCs, and repeat the self-test. If no voltage is present, turn the ignition OFF and check for a short between the injector control and injector return circuits. That resistance also must be greater than 10000 Ω. If it is not greater than 10000 Ω, repair the short circuit, clear the PCM DTCs, and repeat the self-test. If all of those checks pass, move to injector resistance.

Check Injector Resistance

Next, measure resistance across the injector on the component side. Again, measure only the injector that applies to the DTC and the component being diagnosed. The injector resistance should be between 1 Ω - 3 Ω. If resistance is not between 1 Ω - 3 Ω, install a new fuel injector, reset keep alive memory, and repeat the self-test. If resistance is between 1 Ω - 3 Ω and the Power Balance Test pointed to a fuel injector concern, install a new fuel injector as necessary, reset keep alive memory, clear the PCM DTCs, and repeat the self-test. If the injector resistance is in range and the case does not fit that power balance result, continue to the PCM connector check.

Check PCM Connector Condition Before Condemning The Module

For the PCM check, disconnect all PCM connectors and inspect them closely for pushed-out pins and corrosion. Reconnect every PCM connector and make sure each one seats correctly. Then verify whether the concern is still present. If the concern is gone, the system is operating correctly at that time and the issue may have been caused by a loose or corroded connector. If the concern is still present after the circuit checks, injector resistance check, and connector inspection, install a new PCM.

Verify The Repair

Keep verification separate from the testing. After any wiring repair, injector replacement, connector correction, or PCM replacement, clear the PCM DTCs, repeat the self-test, and confirm the code stays gone. The clean diagnostic path here is simple: prove the circuit first, prove the injector next, and only then move to the PCM. For more diagnostic training, visit stepdiagnostics.com.