P0301 is better news than P0300 because your Explorer has already named the cylinder. The catch on a V6 is where that cylinder is. On the 2011–2019 transverse 3.5L V6, cylinder 1 sits on the rear bank against the firewall — the harder half of the engine to reach, and the opposite of what most people assume. So the diagnosis is simpler than P0300 but the access is worse, and knowing that before you start saves an afternoon of looking at the wrong side of the engine bay.
Match the symptom
Select the closest observation. The result changes the first test; it does not name a part to replace.
Classic single-cylinder misfire. At idle nothing masks the missing contribution. Pull the freeze frame before touching anything — it records where the misfire actually happened.
Confirming the cylinder 1 repair held
Write down the freeze frame and all six cylinder counters before clearing anything. Clearing first destroys the record of conditions you need to reproduce for verification.
Then drive the rpm, load and temperature window the freeze frame recorded and watch the cylinder 1 counter. Zero counts across those exact conditions is the proof. A dashboard that stays dark during a gentle drive is not, particularly for a fault that only appeared under load.
While you are in there, consider whether the other two rear-bank plugs are due as well. If cylinder 1's plug was original at high mileage, cylinders 2 and 3 almost certainly are too — and doing them while access is already open is far cheaper than returning for the same job in six months.
What can set P0301—and how to separate it
The order below is evidence-driven, not a universal probability ranking. Vehicle year, repair history, companion codes and the operating condition in freeze frame change where diagnosis should begin.
| Possible cause | Evidence that supports it | First useful test |
|---|---|---|
| Worn spark plug on cylinder 1 | High mileage with no rear-bank service history; plug visibly worn compared with the front bank | Remove the cylinder 1 plug and compare it against the others, particularly against a front-bank plug |
| Failing coil on cylinder 1 | Misfire follows the coil when moved; carbon tracking in the boot; broken connector lock | Swap the cylinder 1 coil with another on the same bank, clear the code and see whether the misfire moves |
| Injector fault on cylinder 1 | Misfire stays after plug and coil are eliminated; injector quiet or resistance out of line | Listen with a stethoscope, compare resistance, then run the scan tool's injector test |
| Vacuum leak affecting that runner | Positive Bank 1 fuel trims alongside the misfire; lean codes stored; leak found on smoke test | Smoke-test the intake with attention to the rear-bank manifold face |
| Coolant entering the cylinder | Milky oil, coolant loss with no external leak, white smoke or a sweet exhaust smell | Inspect the oil and run a combustion-gas test before buying ignition parts |
| Low compression on cylinder 1 | Misfire will not follow any component; relative compression down on that cylinder | Run relative compression from the scan tool, then a mechanical compression or leak-down test |
Cylinder 1 is on the rear bank — plan for that
On the 2011–2019 Explorer with the transverse 3.5L V6, Bank 1 is the rear bank against the firewall and it contains cylinders 1, 2 and 3. Cylinder 1 itself sits toward the accessory-drive end.
This matters practically rather than academically. The rear bank is the awkward one. Access to its coils and plugs is restricted, the job takes longer, and a labour quote for rear-bank work is legitimately higher than for the front. If someone has quoted you a low figure for a cylinder 1 coil on this engine, confirm they know which bank it is on.
It also explains why cylinder 1 misfires disproportionately often on these vehicles. Rear-bank plugs get skipped during service because reaching them is inconvenient, so they stay in the engine long past their interval while the front three get replaced on schedule.
For 2020-onward Explorers the platform changed to a longitudinal rear-wheel-drive layout, so confirm the orientation for your own generation rather than assuming this applies.
The coil swap, adapted for a V6
The principle is the same as on any engine: move the suspect coil to a different cylinder, clear the code, and see whether the misfire follows it. If it does, the coil is faulty and you have proved it for free. If it stays on cylinder 1, the coil is fine and you have eliminated the most common cause.
The practical adaptation on a transverse V6 is to swap within the same bank where possible. Moving a coil from cylinder 1 to cylinder 2 keeps you working in one area rather than reaching across the engine twice, and it answers the same question.
Label both coils before you move them. On a six-cylinder engine with restricted access it is genuinely easy to lose track, and a test you cannot interpret is worse than no test.
Check the oil first on the V6 engines
The 3.5L and 3.7L V6 engines use an internal water pump driven by the timing chain. When its seal fails, coolant leaks into the oil rather than onto the ground — which is why the loss leaves no puddle to find.
Coolant reaching a combustion chamber causes misfire. The same contamination also accelerates timing chain wear, which disturbs valve timing and can cause misfire by a second route. Either way, ignition parts will not fix it.
Pull the dipstick and look before you order anything. Milky or coffee-coloured oil, or a level that has risen, is the pattern. It takes two minutes and it can save you the entire cost of a set of coils.
Why blanket replacement is worse on a V6
- P0301 already named the cylinder — replacing all six throws that away
- Rear-bank labour is significantly higher, so the waste is larger than on an inline engine
- It disturbs five healthy connectors in an area that is awkward to work in
- If the cause is an injector, compression or coolant, new coils change nothing
- The coil swap answers the same question at no cost
Save these scan-data clues
Freeze frame is a snapshot of conditions when the PCM matured the fault. It can distinguish an idle-only problem from a load, cold-start or monitor-completion problem. Clearing first throws that context away.
- Misfire counters for every cylinder, confirming cylinder 1 genuinely dominates
- Engine coolant temperature, separating a cold-start fault from a warm one
- Bank 1 short and long-term fuel trim; positive trims suggest air or fuel rather than ignition
- Engine load and rpm when the counters climbed
- Any companion codes — lean codes, a P0016 or a second misfire code change the order of work
- Vehicle speed and throttle position at the time of the fault
A practical diagnostic workflow
- 01Check the oil for coolant contamination
Two minutes with a dipstick on a V6 Explorer. Milky oil means the internal water pump, not a coil, and it changes the entire direction of the repair.
- 02Confirm cylinder 1 really is dominating
Read all six counters. If cylinders 1, 2 and 3 are all climbing, you have a rear-bank problem rather than a single failed part, and the diagnosis changes accordingly.
- 03Establish which bank cylinder 1 is on
On the 2011–2019 transverse V6 it is the rear bank against the firewall. Confirm for your own generation before planning access, because getting this wrong wastes an afternoon.
- 04Ask when the rear-bank plugs were last changed
If the answer is never, or nobody knows, that is a strong lead. Rear-bank plugs routinely outlive their interval on this platform because they are inconvenient to reach.
- 05Inspect the cylinder 1 plug and compare
Compare it against a front-bank plug in particular. A visible difference in wear between banks tells you the service history even when the paperwork does not.
- 06Swap the coil within the same bank
Move the cylinder 1 coil to cylinder 2 or 3, label both, clear the code and drive. If the misfire follows the coil you have found it without spending anything.
- 07Test the injector on that cylinder
With plug and coil eliminated, listen to the injector, compare its resistance with the others, and use the scan tool's injector test where available.
- 08Check compression when nothing moves the fault
A misfire that will not follow any component is mechanical. Relative compression first, then a mechanical compression or leak-down test if the numbers look wrong.
Do not replace all six coils because one cylinder misfired — the waste is larger on a V6 than anywhere else because half the work is rear-bank labour. P0301 already named the cylinder. Swap the coil first, and check the oil before that. On a 3.5L or 3.7L, milky oil means the internal water pump is your problem and no ignition part will touch it.
P0301 repair cost comparison
These are planning ranges gathered from public U.S. estimate data, not quotations. Your figure moves with local labour rates, model year, engine and whether the shop bills diagnosis separately. Use them to judge whether a quote is reasonable — not to decide what is wrong.
| Repair | Parts only | Shop total | DIY difficulty | Notes |
|---|---|---|---|---|
| Oil and coolant inspection | $0 | Part of diagnosis | Trivial | Rules out the expensive scenario before anything is bought |
| Coil swap diagnostic | $0 | Part of diagnosis | Moderate on the rear bank | Identifies or eliminates the most common cause at no cost |
| Single ignition coil — rear bank | Moderate | Higher labour than the front bank | Moderate to advanced | Replace the one you proved faulty, not all six |
| Spark plugs — rear bank set | Moderate for three | Noticeably higher labour | Advanced on the transverse V6 | Worth doing all three while access is open |
| Injector diagnosis and replacement | Higher on direct-injection engines | Get a quote | Advanced | Only once plug and coil are eliminated by testing |
| Internal water pump and timing repair | Around $1,500 | Roughly $1,500–$3,500 | Not realistic for most owners | Where coolant contamination is confirmed |
Why the model year changes the test
Two things change everything on an Explorer. First, most of these engines are V6s, so Bank 1 and Bank 2 are real, separate halves of the engine — and on the 2011–2019 transverse V6, Bank 1 is the rear bank against the firewall, which is the harder one to reach. Second, the platform changed completely for 2020: the engine turned from transverse to longitudinal when the Explorer went back to rear-wheel drive. Confirm your generation and engine before applying any location-specific advice on this page.
- On the 2011–2019 transverse 3.5L V6, cylinder 1 is on the rear bank against the firewall, with cylinders 2 and 3. That is the harder bank to reach and the opposite of what most people assume.
- Rear-bank plugs are frequently skipped during service on this platform, which is why cylinder-specific misfires appear there disproportionately often.
- The 3.5L and 3.7L V6 use an internal water pump that can leak coolant into the oil, causing misfire and accelerating timing chain wear.
- The Explorer changed to a longitudinal rear-wheel-drive platform for 2020, so confirm cylinder and bank orientation for your generation rather than assuming.
P0301 FAQ
Where is cylinder 1 on a Ford Explorer?+
On the 2011–2019 transverse 3.5L V6, on the rear bank against the firewall, toward the accessory-drive end. That is the harder bank to reach. Confirm separately for 2020-onward vehicles, which use a longitudinal layout.
Can I drive with P0301?+
Briefly and gently if the light is steady, and not at all if it is flashing. On a V6, check the oil first — milky oil means coolant is getting in and you should not drive on it.
Why is P0301 more expensive to fix on an Explorer?+
Because cylinder 1 is on the rear bank of the transverse V6, where access is restricted. The parts cost the same but the labour is higher, and that is legitimate rather than a shop overcharging.
Should I replace the coil or the plug first?+
Inspect the plug first, because it costs nothing and often shows the fault. Then swap the coil within the same bank. Between those two free steps you will identify most P0301 faults.
Why do rear-bank cylinders misfire more often?+
Usually because their plugs are older. Rear-bank plugs are awkward to reach and get skipped during service, so they stay in the engine long past their interval while the front three get replaced.
What does milky oil mean on my Explorer?+
Coolant is mixing with the oil. On the 3.5L and 3.7L that most often means the internal water pump seal has failed, and it explains misfire without any ignition part being at fault.
Why did P0301 return after new plugs and coils?+
Because the fault was never in the ignition system. A misfire that survives both is usually an injector, low compression, or coolant reaching the cylinder.
Can I swap the coil to any cylinder?+
Any cylinder works for the test, but swapping within the same bank saves reaching across the engine twice on a transverse V6. Label both coils so you can interpret the result.
Ford diagnostic references
These documents explain Ford monitor operation. Exact pinpoint tests, connector views and specifications must be selected for the truck's VIN and model year in current service information.
01Ford 2017 gasoline OBD operation summaryFord EVAP, misfire, fuel and comprehensive-component monitor descriptions↗02Ford 2024–2025 gasoline OBD operation summaryFord monitor logic, enabling conditions and drive-cycle requirements↗03Ford 3.5L V6 cylinder numbering and bank layout guideEstablishes that Bank 1 is the firewall-side bank on the transverse 3.5L V6↗04NHTSA technical service bulletin searchPublic database for confirming whether a bulletin covers your VIN and model year↗05Ford owner manuals and warranty guidesOfficial year- and VIN-specific manual lookup for your vehicle↗