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What P0303 means for your Jeep Grand Cherokee
Your Grand Cherokee's PCM caught cyl 3 misfire. On the 3.6L Pentastar V6, cyl 3 is bank 2 (passenger side, right). The Pentastar has a notorious right-bank cylinder head issue - the W77 right-bank cylinder head develops valve-seat erosion that causes misfires on cyls 2, 4, and 6 (bank 2)... but on Grand Cherokees with the right-bank firing order, cyl 3 can also be affected. Chrysler issued multiple TSBs and an extended warranty (TSB 09-001-13). The 5.7L Hemi follows the COP coil failure pattern.
Top Causes of P0303 on the Jeep Grand Cherokee
45%
#1 CAUSE
W77 Right-Bank Cylinder Head Valve Seat Erosion (3.6L Pentastar)
Chrysler 3.6L Pentastar - especially 2011-2013 - has a known right-bank cylinder head defect. The exhaust valve seat erodes, dropping compression and causing P0301/P0303/P0305 (bank-2 misfires on Grand Cherokee). Chrysler TSB 09-001-13 covers the head replacement under extended warranty (10 yr/150k mi for the right head). If you're under 150k miles, the head is FREE at a dealer.
Head Under Warranty
$0 (TSB 09-001-13)
Out of Warranty
$1,800-$2,800
New W77 Head
$1,200-$1,800
30%
#2 CAUSE
Cylinder 3 Coil Pack Failure (Hemi / Pentastar)
Mopar 4606824AC (Pentastar) or 56028394AB (Hemi). Cyl 3 on Hemi is bank 1 passenger side; on Pentastar V6 it depends on firing order/calibration. Swap test takes 5 minutes.
OEM Coil
$70-$120
Aftermarket
$28-$55
w/Labor
$120-$220
15%
#3 CAUSE
MDS Lifter Collapse (5.7L Hemi)
5.7L Hemi MDS deactivates cyls 1, 4, 6, 7. Cyl 3 is NOT MDS-active, so a true cyl-3 misfire on a Hemi is almost never an MDS lifter. However, MDS-related debris or oil-pressure issues can affect any cylinder. Listen for a tick before chasing this.
Lifter + Pushrod
$1,800-$3,500
MDS Delete Kit
$650-$1,300
Cam if damaged
$2,500-$5,500
Most Affected Grand Cherokee Model Years
| Year | Engine | Primary Cause | Typical Mileage | Notes |
|---|---|---|---|---|
| 2011-2013 | 3.6L Pentastar V6 | W77 valve seat | 60k-130k | TSB 09-001-13 head warranty |
| 2014-2018 | 3.6L Pentastar V6 / 5.7L Hemi | Coil + head | 60k-140k | W77 issue mostly resolved by 2014 |
| 2019-2024 | 3.6L Pentastar / 5.7L Hemi eTorque | Coil pack #3 | 60k-120k | eTorque adds 48V hybrid |
| 2015-2024 | 6.4L 392 Hemi | Coil pack #3 | 60k-140k | No MDS - clean coil job |
TSB info: Chrysler TSB 09-001-13 (W77 right-bank cylinder head defect, extended warranty 10 yr / 150k); TSB 09-001-15 (Hemi MDS lifter inspection).
How to Diagnose P0303 on a Jeep Grand Cherokee
- On a 3.6L Pentastar with P0303, ALWAYS check VIN against Chrysler TSB 09-001-13 FIRST. If your right-bank head qualifies for the extended warranty (10 yr/150k), the dealer fixes it FREE.
- Swap coil 3 with coil 1 (or whichever is electrically adjacent - check firing order). If code follows the coil, replace it. Cheap fix first.
- On a 5.7L Hemi with no tick at idle, swap coil 3 with coil 5 (both bank 1). If code moves, replace the coil. A tick + misfire on cyl 1/4/6/7 = MDS lifter - cyl 3 specifically would be unusual.
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.
P0303 Jeep Grand Cherokee FAQs
Is my Grand Cherokee covered by the W77 head TSB?
If you have a 2011-2013 3.6L Pentastar and the right-bank head shows valve-seat erosion (low compression on cyls 2, 4, 6 or P0301/P0303/P0305), TSB 09-001-13 extends the warranty to 10 years / 150,000 miles. Bring it to a Mopar dealer with the codes.
How do I know if it's the head or just a coil on a Pentastar?
Do a compression test. If cyl 3 reads 15+% lower than the others, the head is the cause - book a TSB inspection. If compression is even, swap coils 3 and 5 to test.
How much does the Pentastar head cost out of warranty?
$1,800-$2,800 at a Chrysler dealer (right head only). New replacement W77 heads run $1,200-$1,800 in parts.
Is the Hemi or Pentastar more reliable in the Grand Cherokee?
6.4L Hemi has the best long-term record (no MDS, no head issue). 5.7L Hemi: watch MDS lifters past 100k. 3.6L Pentastar: 2014+ is much better than 2011-2013 (W77 fix). EcoDiesel: ongoing emissions and oil-cooler problems.