P0204 - Cylinder 4 Fuel Injector
System
Powertrain (Engine & Gearbox)
Technical Description
The control module has detected a fault in the Cylinder 4 Fuel Injector (P0204). The module sees no circuit at all — broken wire, backed-out pin, or a failed sensor. The fault is isolated to cylinder 4, positioned at the flywheel end (exposed to torsional vibration harmonics). This directly impacts individual cylinder volumetric efficiency, firing synchronization, and dedicated harness branch loading.
Multimeter Test Points & Nominal Values
| Test Point / Component | Measurement | Nominal Target Range | Test Condition |
|---|---|---|---|
| Cylinder 4 Injector – Coil Resistance | Resistance (Ω) | 11.5 - 15.5 Ω (port) / 0.5 - 3.0 Ω (direct injection) | Connector disconnected at 20°C (cylinder 4) |
| Cylinder 4 Injector – Injection Pulse at 540° crank angle | Signal (ms) | 2.5 - 4.5 ms idle / 1.5 - 20 ms under load | Engine running |
| Cylinder 4 Injector – Supply Voltage | Voltage (V) | 11.8 - 14.4 V (port) / up to 65 - 90 V boost (direct) | Ignition ON / engine running |
Connector disconnected at 20°C (cylinder 4)
Engine running
Ignition ON / engine running
Oscilloscope Waveform Analysis
1 ms/div, 20 V/divPossible Causes
Open circuit, damaged wiring harness, or disconnected plug at Cylinder 4 Fuel Injector
Flywheel end torsional vibration (cylinder 4): High cyclic vibration harmonics from dual-mass flywheel and transmission input shaft transferred to terminal pins.
Rear cylinder coolant stagnation:Thermal stratification at cylinder head rear bulkhead and harness chaffing against bellhousing casting.
Channel A:Verify dedicated wiring pins and signal pair for circuit A against the schematic.
Chafed or pinched wiring harness along the signal path to Cylinder 4 Fuel Injector
Internal mechanical wear or carbon deposits inside Cylinder 4 Fuel Injector
Defective internal output driver or reference circuit in the control module for Cylinder 4 Fuel Injector
Symptoms
5
Recommended Solution
Compare signal voltage and resistance between circuit A and companion circuit B at module connector.
Swap component on cylinder 4 over to cylinder 1 and clear DTCs to confirm if fault follows.
Inspect wiring harness brackets against transmission bellhousing casting and rear engine mount for vibration chafing.
Verify continuity (< 0.5 Ω) on the signal wire between the component plug and the ECM header connector.
Verify loaded supply voltage and harness terminal pins at Cylinder 4 Fuel Injector.
Check circuit continuity and ground-side voltage drop (< 0.05 V) for Cylinder 4 Fuel Injector.
Perform fuel rail pressure-drop / balance test to identify leaking, stuck, or clogged injectors.
Mechanic's Tip
Pro-tip for cylinder 4: Cylinder 4 sits closest to the flywheel and absorbs powertrain torsional harmonics. Inspect wiring closely for chafing against bellhousing brackets.