P0304 - Cylinder 4 Misfire
System
Powertrain (Engine & Gearbox)
Technical Description
The control module has detected a fault in the Cylinder 4 Misfire (P0304). 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 Ignition Coil – Primary Resistance | Resistance (Ω) | 0.4 - 2.0 Ω | Coil disconnected at 20°C (cylinder 4) |
| Cylinder 4 Ignition Coil – Supply Voltage | Voltage (V) | 11.8 - 14.4 V | Ignition ON at coil B+ pin |
| Cylinder 4 Ignition Coil – ECM Dwell Trigger Pulse | Voltage (V) | Rest ≈ battery voltage, dwell pull to 0 V for 1.5 - 4.0 ms | Engine running or cranking |
Coil disconnected at 20°C (cylinder 4)
Ignition ON at coil B+ pin
Engine running or cranking
Oscilloscope Waveform Analysis
500 µs/div, 50 V/divPossible Causes
Cylinder 4 Misfire is electrically operational but performing outside calibrated tolerance
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.
Chafed or pinched wiring harness along the signal path to Cylinder 4 Misfire
Internal mechanical wear or carbon deposits inside Cylinder 4 Misfire
Defective internal output driver or reference circuit in the control module for Cylinder 4 Misfire
Symptoms
5
Recommended Solution
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 underlying mechanical operation and rule out blockage, vacuum leaks, or mechanical binding.
Verify loaded supply voltage and harness terminal pins at Cylinder 4 Misfire.
Check circuit continuity and ground-side voltage drop (< 0.05 V) for Cylinder 4 Misfire.
Inspect spark plug gap and ceramic insulator for carbon tracking, cracks, or dielectric puncture.
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.