Ram-specific code — factory diagnostic data| DTC Data Sheet | |
| Code | P0300 |
| Vehicle | Ram 1500 (2009-2024) |
| Engine | 5.7L V8 HEMI (Eagle, with MDS) |
| System | IGNITION SYSTEM |
| Fault type | Performance |
| Official meaning | Random / Multiple Cylinder Misfire Detected |
Definition source: Ram factory description. Diagnostic guidance is based on factory-defined fault logic for this code.
Decode any Ram 1500 VIN — free recalls, specs & safety ratings — free VIN decoder with NHTSA data
Looking for the cross-vehicle definition? Read the generic P0300 article for the SAE-defined fault logic that applies to all manufacturers.
P0300 Quick Answer
P0300 on a Ram 1500 Hemi means misfires across more than one cylinder. The two leading causes are spark plugs (the Hemi has TWO plugs per cylinder — 16 total — and many DIY plug changes leave one or two coil-on-plug boots un-seated), and ignition coils failing one or two at a time. MDS lifter problems are a less-frequent but well-documented third cause.
What Does P0300 Mean on a Ram 1500?
The Ram 1500 (2009-2024) stores P0300 when the PCM detects the condition described above. This guide focuses on the 5.7L V8 HEMI (Eagle, with MDS) — the most common configuration on this platform. Diagnostic priorities and likely root causes differ from the generic SAE definition because of platform-specific failure patterns documented below.
Symptoms
- Rough idle, hesitation under acceleration
- Flashing CEL under load — severe misfire, do not drive
- Possible specific-cylinder codes (P0301-P0308) alongside P0300
- Cold-start “lifter tick” if MDS-related
- Fuel economy drop
Common Causes (Most Likely on This Model First)
The 5.7L Hemi has 16 spark plugs (two per cylinder) and 8 coil packs. That’s a lot of failure surface, and Hemi P0300s usually trace to one of:
- Old or fouled spark plugs. Hemi plug life is 100,000 miles on paper but only 60,000-70,000 in real-world driving with MDS oil consumption. Always replace all 16 — never just the 8 on one side.
- Failing ignition coil (single cylinder). COP coils on the Hemi fail one at a time, usually triggering a P030x for the specific cylinder first, then a P0300 as it cascades. Swap-test by moving a suspected coil to another cylinder.
- Un-seated coil boot after plug service. Common mistake on Hemi plug jobs — one of the 16 boots doesn’t click home. The cylinder misfires intermittently. Pull each boot and verify positive seating.
- MDS lifter collapse on cylinders 1, 4, 6, or 7. Same failure mode as GM AFM but at lower rates on the Hemi. Symptoms: ticking on cold start plus P030x for the affected cylinder. Don’t drive an extended period with a collapsed lifter.
- Failing fuel injector (single cylinder). Less common but worth checking. A bad injector triggers a specific P030x.
- Intake manifold gasket leak. Lean misfire under load. LTFT both banks > +10%.
Diagnostic Approach
- Pull misfire counters per cylinder. Specific-cylinder dominance points to coil/plug/injector for that cylinder. Pattern on 1/4/6/7 points to MDS.
- Check freeze frame for RPM and load at fault. Idle-only misfire = ignition (plug/coil); load-only misfire = fuel pressure or injector.
- LTFT both banks. If both > +10%, vacuum leak. If one bank, more localized.
- Pull plugs on the cylinders showing misfires. Look for wet/oily residue (MDS oil), light grey center electrode (correct), white or pale (lean), heavy black soot (rich).
- Coil swap test: move the suspected coil to a clean cylinder, clear codes, drive. If the misfire follows the coil, replace it.
- Verify each coil-on-plug boot is fully seated. A loose boot will misfire intermittently and may pass scan-tool checks at idle.
- On 100k+ trucks: replace ALL 16 plugs as preventive maintenance — total cost of plugs is far less than the labor to chase intermittent misfires.
Possible Fixes
| Fix | When |
|---|---|
| Spark plug replacement (all 16) | Plugs over 60k miles or showing wear / fouling |
| Single ignition coil replacement | Misfire follows the coil when swapped |
| Re-seat coil boot | Loose boot found during inspection |
| MDS lifter / cam service | Tick on cold start with cylinder 1/4/6/7 misfire |
| Intake manifold gasket set | Both-bank LTFT > +10% |
Can I Still Drive With P0300?
Steady CEL = drive carefully to a shop within a week. Flashing CEL = stop driving immediately, get towed if needed — a hot misfire dumps unburnt fuel into the catalytic converter and can destroy it in 15-30 minutes of driving.
How Serious Is This Code?
Moderate. A single weak coil or plug is no immediate threat; persistent severe misfire damages the cat and can wash cylinder walls with fuel. MDS lifter failure left unaddressed can score the camshaft.
Repair Costs
| Repair | Estimated cost (parts + labor) |
|---|---|
| Spark plug replacement (all 16, OE) | $340 – $580 |
| Single ignition coil replacement | $95 – $180 |
| All 8 coils + 16 plugs | $780 – $1,250 |
| MDS lifter / cam service | $1,800 – $3,600 |
| Intake manifold gasket set | $480 – $880 |
FAQ
How many spark plugs does a Ram 1500 5.7L Hemi have?
Sixteen — two per cylinder. Always replace all 16 at once, never just one side. Mixing old and new plugs almost always leads to a return P0300.
What causes random misfire on a Ram 1500 Hemi?
In rough order of frequency: aging spark plugs (over 60k miles), a single failing ignition coil, an un-seated coil boot after recent plug service, and MDS lifter collapse on cylinders 1/4/6/7. Less common: a failing fuel injector or intake manifold gasket leak.
Can I drive my Ram 1500 with P0300?
Steady CEL — yes, briefly, to a shop. Flashing CEL — no. A flashing light means the misfire is severe enough that unburnt fuel is reaching the catalytic converter, where it can destroy the substrate in less than half an hour of driving. Get the truck towed.
Should I delete MDS on my Ram 1500 to prevent P0300?
Many Hemi owners delete MDS for exactly this reason. A proper delete (cam swap, non-MDS lifters, PCM tune) eliminates the oil-consumption and lifter-failure modes and costs $1,800-$3,500. It also voids the powertrain warranty if still in effect. Worth doing on a 100k+ truck where the warranty is gone.