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What P0302 means for your Subaru Outback
Your Outback dropped cyl 2. Subaru boxers lay flat - cyls 1 and 3 are passenger bank, cyls 2 and 4 are driver bank. Cyl 2 is driver side, front. It sees less heat than cyl 1 (which sits next to the cat) but follows the same coil-aging pattern. The EJ25 head-gasket leak that fouls cyl 1 plugs does not usually affect cyl 2 (different head), making P0302 more often a clean coil-or-plug job than P0301.
Top Causes of P0302 on the Subaru Outback
55%
#1 CAUSE
Cyl 2 Ignition Coil Failure (driver bank)
Subaru boxer coil 2 sits on the driver-side head, front. Lower heat exposure than cyl 1 but the same brittle coil insulation fails by 100k miles. Subaru OEM 22433AA640 (EJ25) or 22433AA660 (FB25). Swap-test with coil 4.
OEM Coil
$95-$145
Aftermarket
$35-$65
w/Labor
$130-$220
25%
#2 CAUSE
Worn NGK Iridium Plugs
Subaru specs NGK SILFR6A11 iridium at 60k miles. ALWAYS replace all 4 - boxer plug access is a pain so doubling up labor is wasteful. Gap 0.043". Aftermarket plugs cause repeat misfires.
Plugs (4)
$40-$72
w/Labor
$180-$320
DIY
1-2 hrs
15%
#3 CAUSE
Driver-Side Head Gasket Coolant Intrusion (EJ25)
The 2010-2012 EJ25 head gasket can also leak internally on the driver-side head, allowing trace coolant into cyl 2. Symptoms: P0302 + sweet exhaust smell + slowly dropping coolant level. Pressure-test the cooling system. Different failure mode than the cyl-1 external oil leak.
Head Gasket Job
$1,800-$2,800
Pressure Test
$80-$160
Block Test
$60-$100
Most Affected Outback Model Years
| Year | Engine | Primary Cause | Typical Mileage | Notes |
|---|---|---|---|---|
| 2010-2012 | 2.5L EJ253 | Coil or HG | 100k-160k | Watch for coolant loss |
| 2013-2018 | 2.5L FB25 | Coil pack #2 | 90k-160k | FB25 fixed HG issue |
| 2019-2024 | 2.5L FB25 / 2.4L FA24 | Coil + carbon (FA24) | 40k-100k | FA24 GDI - watch carbon |
| 2010-2019 | 3.6L EZ36 H6 | Coil pack #2 | 100k-180k | 6-cyl boxer rarely misfires |
TSB info: Subaru TSB 09-68-15R (EJ25 head gasket inspection / extended warranty); TSB 11-174-17 (FB25 ignition coil).
How to Diagnose P0302 on a Subaru Outback
- Swap coil 2 with coil 4. Drive 20 miles. If P0302 becomes P0304, replace coil 2.
- Pull plug 2 - oil = head gasket, white = lean, carbon = rich. If plugs are over 70k miles, replace all 4 with NGK SILFR6A11.
- On a pre-2012 EJ25 with P0302 plus coolant loss, do a block test (combustion gas in coolant) to confirm head gasket internal leak.
Want a step-by-step walkthrough specific to your Subaru Outback? Run a $5.99 AI diagnosis report - we narrow the cause to your year, engine, and symptoms.
P0302 Subaru Outback FAQs
Is P0302 less serious than P0301 on a Subaru?
Same root causes, slightly different failure mode. Cyl 2 sees less exhaust heat than cyl 1, so coils last a bit longer. The EJ25 head gasket issue can affect either side - cyl 1 usually external (oil leak), cyl 2 sometimes internal (coolant intrusion).
How much does P0302 cost on an Outback?
Coil: $130-$220 shop / $35-$65 DIY. Plug set: $180-$320. Head gasket (if confirmed): $1,800-$2,800.
Should I do both head gaskets on an EJ25?
Yes - the labor to access one head requires removing the engine in many cases. Doing both gaskets at the same time only adds about $200-$400 in parts but saves $1,000+ in labor later.
Will boxer engines always have ignition coil issues?
All Subaru boxer engines have the same vertical coil-on-plug orientation, which puts the coil insulation directly in the engine bay heat. Coils last 100k miles on average - shorter than equivalent inline-4 setups - but $40-$70 a coil makes replacement cheap.