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What P0301 means for your Jeep Grand Cherokee
On the 5.7L Hemi, P0301 cylinder-1 misfire is most often caused by a failing MDS (Multi-Displacement System) lifter on cylinder 1 (which is one of the four MDS-active cylinders). Like GM's AFM, the Hemi MDS deactivates four cylinders for fuel economy, and the lifters can collapse - causing chronic single-cylinder misfires. On the 3.6L Pentastar, the more common culprit is a worn rocker arm or just a tired ignition coil/plug. A "tick tick tick" at idle on a Pentastar is the classic rocker arm warning.
🎯 Top Causes on the Jeep Grand Cherokee
35%
#1 CAUSE
MDS Lifter Failure (5.7L Hemi)
MDS-equipped Hemis (cylinders 1, 4, 6, 7 on the 5.7L) suffer collapsed lifters after 80k-150k miles. The ECM keeps trying to fire a cylinder whose valve isn't opening properly = chronic misfire. Repair requires removing one or both heads. Many owners pair the repair with an MDS delete tune to prevent recurrence. Don't ignore it - failed lifter can cam-lobe-eat the camshaft, which doubles the repair cost.
Lifters + Cam
$600-$1,200
Labor
$1,000-$2,500
MDS Delete Total
$2,000-$4,000
30%
#2 CAUSE
COP Ignition Coil
Standard Mopar COP coils last 90k-140k miles. Cheap and easy fix to rule out before suspecting MDS. Swap-test cylinder 1 with cylinder 3.
Mopar Coil
$45-$80
Set of 8
$280-$520
w/Labor
$120-$260
20%
#3 CAUSE
Pentastar Rocker Arm Failure (3.6L)
The 3.6L Pentastar (especially 2011-2013) has a rocker-arm/HLA failure issue that produces a "tick" sound and cylinder-1 or cylinder-2 misfire. Replacement is a same-day shop job - one head valve cover and rocker arm replacement on the affected cylinder. Updated rocker design from Chrysler reduces recurrence.
Rocker + HLA
$80-$180
Labor
$300-$600
Total
$400-$800
15%
#4 CAUSE
Spark Plug / Wire Issue
5.7L Hemi has 16 plugs (two per cylinder) - both plugs on cylinder 1 wear together. Replace all 16 at 100k miles. Pentastar 3.6L has standard 6 iridium plugs at 100k. Use Mopar/Champion spec plugs.
Hemi Plugs (16)
$80-$160
Pentastar Plugs (6)
$45-$90
w/Labor
$100-$300
🚗 Most Affected Grand Cherokee Model Years
| Year | Engine | Primary Cause | Typical Mileage | Notes |
|---|---|---|---|---|
| 2011-2017 | 5.7L Hemi w/MDS | MDS lifter | 80k-160k | Class-action discussions ongoing |
| 2011-2013 | 3.6L Pentastar | Rocker arm | 60k-110k | Updated rocker after 2014 |
| 2014+ | 3.6L Pentastar | Coil + plug | 70k-130k | Rocker issues much rarer |
🔧 How to Diagnose P0301 on a Jeep Grand Cherokee
- Identify your engine. 3.6L Pentastar vs 5.7L Hemi - the diagnosis paths are very different.
- Swap-test the coil. If the misfire follows the coil, $50 fix and you're done.
- Listen for ticking (Pentastar). A clear "tick tick tick" at idle on a 2011-2013 Pentastar = rocker arm. Same-day fix with a shop.
- Compression test if MDS-equipped. A collapsed MDS lifter shows up as low compression on cylinder 1 (or 4/6/7). 30+ psi below the others = lifter problem, plan for the bigger repair.
Want a step-by-step walkthrough specific to your Jeep Grand Cherokee? Run a $5.99 AI diagnosis report - we narrow the cause to your year, engine, and symptoms.