Plain English
What P0306 means for your Jeep Grand Cherokee
Your Grand Cherokee threw cyl 6 misfire - and on either engine this is a known pattern. On the 5.7L Hemi, cyl 6 is one of the four MDS cylinders (along with 1, 4, 7); the MDS lifter collapse is the most common 100k+ mile Hemi failure. On the 3.6L Pentastar, cyl 6 is bank 2 (right) - the W77 head's exhaust valve seat erodes most heavily on cyl 6, making it the most common bank-2 P0306 source. TSB 09-001-13 can make this FREE.
Top Causes of P0306 on the Jeep Grand Cherokee
45%
#1 CAUSE
Collapsed MDS Lifter (5.7L Hemi cyl 6)
Cyl 6 is a Hemi MDS-active cylinder. The MDS lifter collapses, bends a pushrod, and often damages the cam lobe. Symptoms: P0306 + metallic tick at idle. Once a pushrod bends, you need the head off. ALWAYS do an MDS delete during the lifter job - cyls 1, 4, 7 share the same hardware.
Lifter + Pushrod
$1,800-$3,500
MDS Delete Kit
$650-$1,300
Cam if damaged
$2,500-$5,500
35%
#2 CAUSE
W77 Right-Bank Head Valve Seat Erosion (3.6L Pentastar)
Cyl 6 is bank 2 (right) on the 3.6L Pentastar. Cyl 6 has the HIGHEST W77 valve-seat erosion rate of any bank-2 cylinder - this is the single most common Pentastar misfire. Chrysler TSB 09-001-13 extends the warranty to 10 yr/150k mi. CHECK YOUR VIN before paying anyone. Out of warranty: $1,800-$2,800.
Head Under Warranty
$0 (TSB 09-001-13)
Out of Warranty
$1,800-$2,800
New W77 Head
$1,200-$1,800
15%
#3 CAUSE
Cylinder 6 COP Coil Failure
Mopar 56028394AB (Hemi) or 4606824AC (Pentastar). Hemi cyl 6 is rear-bank passenger - moderate access. Swap-test with coil 4 (Hemi) or coil 2 (Pentastar).
OEM Coil
$70-$120
Aftermarket
$28-$55
w/Labor
$140-$240
Most Affected Grand Cherokee Model Years
| Year | Engine | Primary Cause | Typical Mileage | Notes |
|---|---|---|---|---|
| 2011-2013 | 3.6L Pentastar V6 | W77 head (cyl 6) | 60k-130k | TSB 09-001-13 free head |
| 2011-2018 | 5.7L Hemi (MDS) | MDS lifter | 60k-160k | Cyl 6 is MDS-active |
| 2019-2024 | 5.7L Hemi eTorque / 3.6L Pentastar | MDS lifter / coil | 40k-120k | eTorque hybrid |
| 2015-2024 | 6.4L 392 Hemi | Coil pack #6 | 60k-140k | No MDS - clean coil |
TSB info: Chrysler TSB 09-001-15 (Hemi MDS lifter inspection - cyls 1, 4, 6, 7); TSB 09-001-13 (Pentastar W77 right-bank head warranty extension 10 yr / 150k mi).
How to Diagnose P0306 on a Jeep Grand Cherokee
- On a 5.7L Hemi, LISTEN at idle. Tick + P0306 = MDS lifter on cyl 6. Skip the coil swap and pull the valve cover.
- On a 2011-2013 3.6L Pentastar, CHECK YOUR VIN against TSB 09-001-13 - cyl 6 is the most common W77 head failure point. If you qualify, the repair is FREE.
- No tick (Hemi) and not TSB-covered (Pentastar)? Swap coil 6 with coil 4 (Hemi) or coil 2 (Pentastar). Code follows the coil = replace it.
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.
P0306 Jeep Grand Cherokee FAQs
Why is cyl 6 the worst cylinder on a Pentastar?
Cyl 6 has the highest W77 valve-seat erosion rate on 2011-2013 3.6L Pentastars. It's bank 2 (right side), and the exhaust valve seat there sees the worst thermal cycling. Of all bank-2 misfire codes, P0306 is the most common.
How do I know if it's MDS or a coil on a Hemi P0306?
Listen at idle. Bad coil = silent. Collapsed MDS lifter = metallic tick. A 5-minute coil swap rules it out. P0306 + tick = open the valve cover.
Should I do an MDS delete with a cyl-6 lifter repair?
Yes - cyls 1, 4, 6, 7 all share the same MDS hardware. One failure means more are coming. MDS delete kit during the lifter job: $650-$1,300 extra, prevents three more $2,500 repairs.
Is the free W77 head repair really still available?
If your Grand Cherokee is under 150k miles and under 10 years from in-service date, yes. TSB 09-001-13 is still active. Bring documented misfire codes (especially P0306) to a Mopar dealer.