OBD codes / P0357
P0357
SeriousIgnition Coil G Primary/Secondary Circuit (Cylinder 7)
A V8 down one cylinder can feel deceptively drivable, but cylinder 7's unburned fuel is still cooking the catalytic converter on that bank. Steady light: short, gentle trips only. Flashing light: catalyst damage is active — ease way off and get it repaired promptly.
What this code means
Coil G is the ignition coil for cylinder 7, so this code only shows up on engines with at least seven cylinders — in practice, V8s and larger. The ECM switches each coil's primary circuit to trigger the spark and verifies the circuit electrically on every firing event; P0357 means coil G's circuit read as open or shorted. This is an electrical failure, distinct from a worn spark plug: the plug can be brand new and this code will still set if the coil windings, connector, or wiring have failed. The likely causes, in rough order: a failed coil, an unplugged or corroded connector, chafed harness wiring on that bank, a blown fuse in the coil feed, and — rarely — the coil driver inside the ECM. With no spark reaching cylinder 7, the companion misfire code P0307 typically sets too, and you'll feel the missing cylinder as a rhythmic roughness, though a V8 can mask a single dead hole better than a four-cylinder can.
Symptoms you might notice
- Misfire on cylinder 7 — uneven idle, subtle rhythmic shake
- Reduced power, most obvious under hard acceleration or towing
- Check-engine light, flashing while misfiring
- Fuel smell at the exhaust
- Companion misfire code P0307 usually present
What it costs to fix
Typical range: $60–$450 · about ~0.2–2 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| Ignition coil (single) | $30–$150 | ~0.2–1 hrs |
| Wiring or connector repair | $5–$50 | ~0.5–2 hrs |
| Spark plugs (while in there) | $20–$100 | ~0.5–1.5 hrs |
Most V8 coils sit on top of the valve covers and swap out quickly, so this is usually a low-labor job. The exceptions are engines where rear cylinders tuck under cowling or intake plumbing, and tight engine bays where reaching cylinder 7 takes patience — wiring faults also add diagnostic time that a simple coil swap doesn't.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0357 for my exact vehicle →
Frequently asked
Does P0357 only apply to V8 engines?
It requires an engine with at least seven cylinders, so in practice you'll see it on V8s, V10s, and V12s. If a scan tool reports P0357 on a four- or six-cylinder engine, doubt the scan before doubting the car — that combination shouldn't exist.
Coil or plug — which one is P0357 blaming?
The coil circuit. This code sets when the electrical path through coil G is open or shorted, which a worn spark plug can't cause. Replace or swap-test the coil and inspect its connector and wiring; do the plug too if it's due, but the plug isn't the trigger.
How much will P0357 cost to fix?
Commonly modest — one coil plus a short labor stint, since most V8 coils are top-of-engine. A wiring repair is cheap in parts but adds diagnostic time. The expensive outcome isn't this repair; it's the catalytic converter you can damage by driving on the misfire too long.
Is it OK to drive my truck with P0357 while towing?
Skip the towing until it's fixed. Heavy load is exactly when a misfire dumps the most unburned fuel into the catalyst and when the engine most misses that cylinder. Light unloaded driving with a steady light is a reasonable stopgap; working the engine hard is not.
Seeing P0357 on your car? Get a diagnosis specific to your exact year, make and model.
Diagnose P0357 for my vehicleRelated trouble codes
Don’t have a scanner yet? A ~$25 Bluetooth adapter reads codes like P0357 from your phone — see our honest guide to the best OBD2 Bluetooth adapters.
Generic OBD-II reference. Manufacturer-specific behavior varies — confirm with a scan tool and, for safety-related codes, a professional inspection.