OBD-II Code
P2302
Severity
Not yet reviewed
Nobody on our side has assessed this code yet, so we are not going to guess at how serious it is.
Can you drive it
We cannot say
Treat it as unknown until a shop reads it with live data. If the check-engine light is FLASHING, stop driving as soon as it is safe to — that means an active misfire, whatever the code.
Indicative cost (USD)
$15–$400
From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
$15 (boot + dielectric grease) to $400 (full coil set on a V8).
P2302 means the PCM detected a fault on the SECONDARY circuit of ignition coil A — the high-voltage side that fires the spark plug, typically diagnosed by the PCM watching the burn time (spark-line duration on a scope, usually 0.8-2.0 ms for a healthy coil firing a fresh plug) or by detecting that the expected 15-40 kV secondary firing voltage demand exceeded the coil's capacity.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then follow the diagnostic notes further down this page, in the order they are written.
They are written in the order a shop works this code, cheapest checks first. Where they name a component, inspect its wiring and connector before replacing it.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
Read the full diagnostic procedureP2302 means the PCM detected a fault on the SECONDARY circuit of ignition coil A — the high-voltage side that fires the spark plug, typically diagnos…
P2302 means the PCM detected a fault on the SECONDARY circuit of ignition coil A — the high-voltage side that fires the spark plug, typically diagnosed by the PCM watching the burn time (spark-line duration on a scope, usually 0.8-2.0 ms for a healthy coil firing a fresh plug) or by detecting that the expected 15-40 kV secondary firing voltage demand exceeded the coil's capacity. Open-secondary is the most common P2302 subcondition — the coil's secondary winding has failed open, or the boot/spring contact down to the plug terminal has carbon-tracked, corroded, or burned through.
Cheapest-first ladder
- Pull coil A and inspect the spark-plug boot for carbon tracks (black wandering lines on the inside of the boot insulation), oil contamination, or arc-through holes — a $15 boot + dielectric grease often resolves what looks like a $180 coil failure.
- Pull the plug and read it — a normal-but-dead plug with no burn marks confirms no spark reached it; a sooty plug with normal gap confirms the secondary side fired but the plug was fouled.
- Ohm the coil's secondary winding (most multimeters with a high-ohms range will read it through the boot or plug-tower) — spec is typically 5K-25K ohms depending on platform; an open reading (OL) confirms a failed secondary winding.
- On a scope with a secondary pickup (kV probe), watch the firing line and burn line during a snap-throttle — a firing line above 25 kV with a short burn line indicates a worn plug or wide gap stressing the coil; a flat or missing burn line indicates open secondary. Expensive-misdiagnosis caveat: swap coil A to an adjacent cylinder before replacing — if P2302 follows the coil, it's the coil; if it stays, the spark plug, plug well, or harness is the problem. A $40 coil swap-test saves $80.
Vehicle-specific patterns2004-2010 Ford 4.6L/5.4L 3V Triton (F-150, Crown Vic, Expedition) is the king of P2302 — the long extension boot down into the deep plug well traps m…
- 2004-2010Ford 4.6L/5.4L 3V Triton (F-150, Crown Vic, Expedition) is the king of P2302 — the long extension boot down into the deep plug well traps moisture, oil mist from leaking valve-cover gaskets, and carbon residue, all of which carbon-track the boot and short the secondary to the cylinder head; replacing the boot + spring contact + dielectric grease fixes 70% of P2302 cases on this engine without touching the coil.
- 2005-2014GM LSx V8 (LS1/LS2/LS3) mounts COPs on the valve covers where heat soak degrades the boot rubber — boots get hard and crack around 80-100K miles.
- 2011+Ford 5.0 Coyote uses a shorter boot than the Triton but still sees boot-tracking around 90K.
- 2007-2018Toyota 2GR-FE / 2AZ-FE secondary failures are typically full-coil failures rather than boot-only issues — Toyota's coil tower design is more sealed against moisture than the Ford Triton. Mazda RX-8 Renesis rotary uses paired trailing and leading coils (not strictly P2302 territory but the secondary-circuit symptom is identical) — the leading coils fail first around 50-70K miles from the rotary's high firing frequency. Common pattern: coil A usually = cylinder 1 but verify against the OEM wiring diagram.
Estimated repair$15 (boot + dielectric grease) to $400 (full coil set on a V8).
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