P0304 Chevy Silverado: Cylinder 4 Misfire Diagnosis and Fix

P0304 on a Chevy Silverado indicates a misfire specifically in cylinder 4. Unlike P0300 (random multi-cylinder misfire), P0304 pinpoints the exact cylinder — which makes diagnosis significantly easier. Cylinder 4 is on the passenger side of a GM V8 engine — the second cylinder from the front on the passenger bank. Here’s how to diagnose and fix it.

Watch a cylinder-specific misfire traced to a failed ignition coil — the same plug, spark and coil checks apply to P0304.

What P0304 Means

The ECM monitors crankshaft speed via the crankshaft position sensor. When a cylinder misfires (incomplete combustion), the crank briefly decelerates as that cylinder fails to contribute its power stroke. The ECM detects this deceleration and logs which cylinder caused it. P0304 means cylinder 4 specifically is misfiring — either consistently or intermittently enough to trigger the threshold.

Cylinder 4 Location on GM V8

On GM V8 engines (LS, Vortec, EcoTec3): the driver’s side cylinders are 1-3-5-7 front to back. The passenger’s side cylinders are 2-4-6-8 front to back. Cylinder 4 is the second cylinder from the front on the passenger side of the engine.

Most Common Causes of P0304

On 4.8L/5.3L/6.0L Vortec and EcoTec3 trucks: bad spark plug in cylinder 4 (worn or fouled), failed or cracked ignition coil on cylinder 4, defective fuel injector on cylinder 4 (stuck closed or leaking), broken ignition wire/coil boot, low compression in cylinder 4 (worn rings, burnt valve, or bent valve from earlier engine damage), or a faulty cylinder 4 lifter on AFM-equipped trucks (2007+ 5.3L — the AFM lifters on cylinders 1/4/6/7 are the ones that deactivate and fail).

Diagnosis in Order

Step 1: Swap the cylinder 4 ignition coil with the cylinder 3 coil. If the misfire moves to P0303, the coil was the cause — replace it ($30–60). Step 2: If coil swap doesn’t move the misfire, inspect the spark plug on cylinder 4. Replace if fouled, cracked, or showing abnormal wear. Step 3: If coil and plug are good, swap the cylinder 4 fuel injector connector with an adjacent cylinder. A lean or rich code shift confirms injector issue. Step 4: If above checks are clean, do a compression test on cylinder 4. Low compression (below 120 PSI or more than 15% lower than adjacent cylinders) indicates an internal engine issue.

AFM Connection on 5.3L Trucks

On 2007–2021 5.3L Silverados, cylinder 4 is one of the AFM cylinders that deactivates. A failed AFM lifter on cylinder 4 causes a persistent P0304 that doesn’t respond to coil, plug, or injector replacement. If standard diagnosis doesn’t find the misfire source, this is the likely culprit. See our AFM delete guide. Related: P0300 random misfire guide.