P2301
Ignition Coil "A" Primary Control Circuit High
- Severity
- High
- Driving
- Short journeys only
The control circuit for ignition coil "A" is reading high, or the module sees nothing switching on it at all. That normally means the circuit is open somewhere - the connector off, a broken wire, a pushed-back pin, or a coil whose primary winding has burnt through. A short to battery positive reads the same way. The coil letter is the manufacturer's designation and does not necessarily correspond to the cylinder number - the vehicle's own documentation says which is which, and a misfire code stored alongside will usually name the cylinder directly.
Possible causes
- CommonCoil connector unplugged, or pushed on without latching
- CommonFailed ignition coil with an open primary winding
- CommonBroken wire or a pin pushed back out of the connector
- PossibleLost power feed to the coil - a blown fuse or a failed relay
- PossibleControl wire shorted to battery positive
- RareFailed driver inside the control module
What you might notice
- Misfire - the engine shaking, especially at idle
- Loss of power and hesitation
- Check engine light on, or flashing
- Poor fuel economy
- Smell of unburnt fuel from the exhaust
What to check, in order
- Check the connector is fully latched before anything else. A coil disturbed during other work and not clicked home is a common cause and costs nothing to rule out.
- Check the coil's power feed with the ignition on. One side of the primary is fed from a fuse or relay, and a lost feed looks identical to a broken control wire from the module's side.
- Measure the coil's primary resistance. An open winding reads infinite, which confirms the coil without any further testing.
- If several coils report this together, check the shared feed and earth first. Coils rarely fail in groups; fuses, relays and earth points do.
- Swap the suspect coil with one from a neighbouring cylinder and see whether the fault follows it. This is the single most effective test available and it costs nothing - but only do it on engines where the coils are genuinely interchangeable.
- Do not order a control module on the strength of this code. A failed driver inside the module does produce it, but it is the last thing to suspect, not the first.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.