Ram-specific code — factory diagnostic data| DTC Data Sheet | |
| Code | P0306 |
| Vehicle | Ram 1500 (2009-2024) |
| Engine | 5.7L V8 HEMI (Eagle, with MDS) |
| System | IGNITION SYSTEM |
| Fault type | Performance |
| Official meaning | Cylinder 6 Misfire Detected |
Definition source: Ram factory description. Diagnostic guidance is based on factory-defined fault logic for this code.
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Looking for the cross-vehicle definition? Read the generic P0306 article for the SAE-defined fault logic that applies to all manufacturers.
P0306 Quick Answer
P0306 on a Ram 1500 Hemi means misfires localized to cylinder 6 — and cylinder 6 IS one of the four MDS-deactivated cylinders (1, 4, 6, 7). That makes lifter collapse a strong suspect alongside the usual ignition/fuel causes. The diagnostic order on a Hemi P0306: listen for a cold-start tick (lifter), then pull the plugs (oil-fouled?), then swap-test the coil, then injector.
What Does P0306 Mean on a Ram 1500?
The Ram 1500 (2009-2024) stores P0306 when the condition described above is met. This guide focuses on the 5.7L V8 HEMI (Eagle, with MDS) — the most common Ram 1500 powertrain. The platform-specific failure patterns documented below differ from the generic SAE definition.
Symptoms
- Rough idle, hesitation
- Cold-start tick from top of engine = lifter suspect
- P0306 specific code, possibly with P0300
- Flashing CEL under load = severe misfire, stop driving
- Possible specific tick that quiets when MDS would activate
Common Causes (Most Likely on This Model First)
- Collapsed MDS lifter on cylinder 6. Cyl 6 is one of the four MDS cylinders. A lifter that loses oil pressure stops following the cam profile. Tell: cold-start tick from the top of the engine that quiets after warmup.
- Oil-fouled spark plugs (cyl 6). MDS oil consumption fouls plugs on the deactivated cylinders. Replace all 16 plugs as a set.
- Failing coil pack on cyl 6. Standard COP failure. Swap-test confirms.
- Failing fuel injector on cyl 6. Clogged or stuck-closed. Less common than ignition issues.
- Compression loss on cyl 6. Verify if everything else checks good. Compression test.
Diagnostic Approach
- Listen for top-end tick on cold start. Stethoscope on each valve cover. Persistent tick = MDS lifter.
- Pull the two plugs on cylinder 6 (passenger side, third from front). Look for oil fouling (heavy black wet residue).
- Swap coil with a clean cylinder. If misfire follows, replace.
- Listen for injector clicking on cyl 6.
- Compression test if electrical/ignition all checks good.
- On 5.7L: read MDS solenoid command vs. lifter behavior on a scan tool that supports MDS-specific live data.
Possible Fixes
| Fix | When |
|---|---|
| MDS lifter service / cam replacement | Cold-start tick on cyl 6, oil fouling visible |
| MDS-delete kit (preferred long-term) | Recurring lifter issues, out of warranty |
| Spark plugs (all 16) | Plugs > 60k or fouled |
| Single ignition coil | Misfire follows the coil when swapped |
| Fuel injector (cyl 6) | Injector electrically dead |
Can I Still Drive With P0306?
Steady CEL: drive briefly to a shop, especially if the engine ticks. Flashing CEL: tow it. Continued driving with a collapsed MDS lifter scores the cam, turning a $1,400-$2,400 lifter service into a $3,500+ cam-and-lifter rebuild.
How Serious Is This Code?
Moderate to high if MDS lifter is the cause. The longer it runs, the more expensive.
Repair Costs
| Repair | Cost |
|---|---|
| Spark plugs (all 16) | $340 – $580 |
| Single ignition coil | $95 – $180 |
| Single fuel injector | $280 – $580 |
| MDS lifter service | $1,800 – $3,600 |
| MDS-delete kit | $1,800 – $3,500 |
FAQ
Is cylinder 6 an MDS cylinder on the Hemi?
Yes. The Hemi MDS system deactivates cylinders 1, 4, 6, and 7 under light load. That makes cylinder 6 prone to the MDS-specific failure modes (lifter collapse, oil-fouled plugs) on top of the usual misfire causes.
How do I know if my Ram P0306 is an MDS lifter?
Listen for a top-end tick on cold start that quiets after warmup. Use a stethoscope on the passenger valve cover. Heavy oil fouling on the cyl 6 plugs is another sign. A scan tool that reads MDS solenoid command and lifter response (most professional tools support this) gives definitive confirmation.
Should I MDS-delete my Ram 1500 to prevent P0306?
For out-of-warranty Hemis with recurring lifter issues — yes, it’s the most reliable long-term fix. Costs $1,800-$3,500 done correctly (cam swap, non-MDS lifters, PCM tune). Eliminates the failure mode permanently.
How much to fix P0306 on a Ram 1500?
Plug change (all 16): $340-$580. Single coil: $95-$180. MDS lifter service or delete: $1,800-$3,500. Catch it before extended driving damages the cam — that turns a $2,000 fix into a $4,500 rebuild.