P0304 on a Ram 1500
P0304 means cylinder 4 Misfire Detected. On the 1500, a few causes come up far more than others.
What P0304 usually means on a 1500
P0304 flags a misfire on cylinder 4 of the Ram 1500, and on the 5.7 HEMI that is a notable location because cylinder 4 is one of the cylinders that shuts off under MDS cylinder deactivation. The MDS cylinders are exactly where the HEMI's collapsed-lifter and worn-cam-lobe problem tends to appear, so a cylinder-4 misfire accompanied by a tapping noise should be treated as a possible valvetrain issue. That said, always rule out the cheap causes first, the coil, plug, and injector on that cylinder.
Most common causes on the 1500
- HEMI MDS lifter or cam lobe on cylinder 4
Cylinder 4 is an MDS cylinder; a collapsed lifter or flattened lobe there is a well-documented HEMI failure with a tick.
- Coil or plug on cylinder 4
Rule out ignition first with a swap test; it is cheap and quick.
- Cylinder 4 fuel injector
A failing injector starves that cylinder and imitates an ignition problem.
- Low compression on cylinder 4
Lifter-related damage or a burnt valve shows as a mechanical misfire confirmed by leak-down.
What P0304 costs to fix on a 1500
The ignition-parts outcome is inexpensive, but the valvetrain outcome is not: a HEMI lifter and camshaft repair runs well into the four figures because of the extensive labor, and a wiped lobe can send debris through the engine. Because cylinder 4 is an MDS cylinder, take a tick seriously and inspect before assuming a simple coil will fix it.
Year, engine and mileage change the answer. Start a case and Redline weighs these causes against what your car shows, then names the check that would settle it.
1500 owners also ask
Why do HEMI misfires so often land on cylinders like 4?
The 5.7 HEMI deactivates specific cylinders under MDS to save fuel, and those cylinders see the collapsed-lifter and worn-cam problem the engine is known for. Cylinder 4 is one of them, which is why a P0304 with a tick points toward the valvetrain.
Does disabling MDS fix or prevent the lifter problem?
It does not undo damage already done, and it is a workaround rather than a repair. Some owners use a tuner or device to keep the cylinders active in hopes of reducing wear, but if a lifter has already collapsed, the camshaft and lifters still need inspection and likely replacement.
Other codes on the Ram 1500
Related symptoms
Based on widely reported patterns for this model; individual causes vary by year, engine and history. Generic P0304 behavior is covered on the main P0304 page. Confirm with a scan tool before buying parts.
P0304 on your 1500?
Every problem becomes a Case. Tell Redline what your 1500 is doing: it shows what the evidence supports, what’s still missing, and what to check next, before you approve a repair.
“Inner pad ~1 mm. Outer pad 3 mm.”
Next: check the slide pins move freely before buying parts.