P030D
Ignition B Control Signal Circuit/Open.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 3
- AreaIgnition system or misfire
- 0D
- FaultThe specific fault in that area
What it means
P030D means the engine control unit has detected an open circuit on the Ignition B control signal, the line it uses to trigger one of the ignition coil drivers or coil circuits. The control unit commanded the circuit and saw no expected electrical response, or saw a voltage that indicates a break. Which coil or bank 'B' refers to depends on the vehicle and engine, so check the manufacturer's wiring information.
Symptoms
- Engine warning light on
- Misfire, rough running or hesitation under load
- Hard starting or extended cranking
- Loss of power or engine running in a reduced-power mode
- Poor fuel economy
- Engine stalling in some cases
Possible causes
- Open circuit, chafed wire or high resistance in the ignition control signal wiring between the engine control unit and the coil or driverlikely
- Corroded, loose or pushed-out terminals at the ignition coil connector or engine control unit connectorlikely
- Faulty ignition coil or integrated coil driver that is not responding to the control signallikely
- Missing or poor power supply or earth to the ignition coil or driver, which can mimic an open signal circuitpossible
- Wiring damage from heat, vibration or rodent chewing, or from previous repair workpossible
- Internal fault in the engine control unit output driverrare
How to diagnose
- Read all stored and pending codes and the freeze frame data. Note engine load, temperature and rpm when the code set, and check for any misfire codes alongside.
- Find in the manufacturer's information which circuit is Ignition B on this engine, and which coil or coils it controls.
- Visually inspect the coil connector, harness routing and engine control unit connector for damage, corrosion, water ingress, bent or loose pins and heat damage.
- With the ignition off, check connector terminal tension and gently wiggle-test the harness with the engine running to see if the fault or a misfire appears.
- Check the coil power supply and earth at the coil connector against the specified values.
- Test the control signal wire for continuity from the engine control unit connector to the coil connector, and check for short circuits to earth or voltage.
- Swap the suspect coil with a known good one, if the layout allows, and see whether the fault follows the coil.
- If wiring and the coil check out, test the control unit output signal with an oscilloscope per the manufacturer's procedure before considering the control unit.
How to fix
- Repair or replace the damaged wiring section using proper soldered or crimped and sealed joints, following the manufacturer's repair guidance.
- Clean, repair or replace corroded or damaged connectors and terminals.
- Replace the faulty ignition coil or coil driver, and check the spark plugs at the same time as they may be worn or damaged by the misfire.
- Restore a faulty power or earth supply to the coil circuit.
- Replace or repair the engine control unit only after all wiring and component faults are ruled out, and have it coded to the vehicle as required.
Can I keep driving?
Short, gentle journeys to a workshop are usually acceptable, but avoid heavy loads and high revs. If the engine is misfiring badly or the warning light flashes, stop driving, as unburnt fuel can damage the catalytic converter.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.