P0204Powertrain
Powertrain · SAE
Injector Circuit Cylinder 4 — Malfunction
Meaning
The ECM has detected an electrical fault in the injector control circuit for cylinder 4. The control signal is absent, out of range, or shorted. The injector may fail to actuate correctly, resulting in a misfire on cylinder 4.
Common causes
- Cylinder 4 injector open circuit or short circuit
- Damaged or corroded wiring/connector at cylinder 4
- Injector winding resistance out of specification
- Internal ECM driver failure
- Wiring harness short to ground or to battery voltage
- Loose or corroded ECM connector pins
Symptoms
- Malfunction indicator lamp (MIL) illuminated
- Cylinder 4 misfire
- Rough idle and vibrations
- Elevated unburned HC emissions
- Reduced engine power
- Possible limp-home mode active
Severity
High: persistent cylinder 4 misfire risks catalytic converter damage and causes significant loss of driveability.
What to do
- Measure cylinder 4 injector resistance (typical 12–16 Ω gasoline, 0.5–2 Ω diesel CR)
- Inspect injector wiring and connector for damage, corrosion or breaks
- Check supply voltage and control signal at the injector connector with an oscilloscope
- Replace the injector if resistance is out of specification
- If the fault persists after injector replacement, inspect the ECM driver stage