A generic coil circuit fault where the ECU has not identified which cylinder. Usually a coil, a plug lead or a wiring fault common to the pack.
P0350 — also written PO35O, P 0350, 0350 — is the OBD-II code for ignition coil primary/secondary circuit. Same code, same fix: this page covers every spelling of it.
P0350 is a engine fault code, typically costing £70–£480 to put right in a UK garage.
What causes P0350?
- Failed ignition coil
- Damaged coil harness connector
- Water in the plug wells
- Chafed coil supply wire
How P0350 is fixed
- Test each coil's primary resistance
- Replace the faulty coil and its connector
- Dry and reseal the plug wells
- Fit plugs at the same time if overdue
P0350 repair cost in the UK
Most P0350 repairs land between £70–£480 including parts and labour. The spread is wide because the cheap fix (a sensor, a hose, a leak) and the expensive fix (a major component) throw the same code — which is why a proper diagnosis before parts are bought saves the most money.
Can you drive with P0350?
Drive gently and briefly. A flashing engine light means an active misfire that will damage the catalytic converter.
Urgency: high.
What P0350 is telling you
The ECU runs continuous plausibility checks against what a good engine should be doing. When a reading strays outside that model for long enough, this code is stored and the light comes on.
On P0350 specifically — ignition coil primary/secondary circuit — the stored code records the moment that check failed, not the moment the part gave up. That gap is why two cars with the same code can need completely different repairs.
How P0350 is diagnosed properly
Each of the known causes is ruled in or out in cost order, cheapest and most likely first. On P0350 that means working through them like this:
- Failed ignition coil — checked for level and condition first, as the cheapest possible cause and a common one.
- Damaged coil harness connector — checked with the loom flexed and the engine warm, because a wiring fault that is intermittent when cold shows itself under heat and vibration.
- Water in the plug wells — opened, inspected for green corrosion and spread pins, and back-probed rather than unplugged, so the reading is taken with the circuit live.
- Chafed coil supply wire — checked with the loom flexed and the engine warm, because a wiring fault that is intermittent when cold shows itself under heat and vibration.
An hour of diagnostic time on P0350 routinely saves more than it costs, because the alternative is buying the most expensive part on that list and hoping.
The repairs that actually clear P0350
- Test each coil's primary resistance
- Replace the faulty coil and its connector
- Dry and reseal the plug wells
- Fit plugs at the same time if overdue
After the repair the code is cleared and the car is driven until the relevant readiness monitor completes, rather than handed back as soon as the light goes out. A code that has only been erased will come straight back on the next drive cycle.
What happens if P0350 is ignored
This is a stop-and-sort fault rather than a wait-for-the-service fault. Ignoring it risks turning a sensor-money repair into a component-money one.
For reference, P0350 typically lands at £70–£480 all-in at an independent garage in the UK — main-dealer quotes for the same job usually sit above that.
Getting P0350 looked at
Bob's Mechanical Repairs is an independent garage in Birnam, Dunkeld, Perthshire, with 32 years of Bob's experience on the tools. If P0350 is showing on your car, bring the scan results with you — we will read the live data ourselves, tell you which of the causes above it actually is, and price the repair before any work starts.