What it means
The ignition B control signal circuit is open — typically the PCM drive line for the first ignition coil group has lost continuity.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The engine control module sends ignition commands through the Ignition B control signal circuit to the coil or coil group assigned to that circuit by the vehicle wiring. P030D sets when the module detects an open or loss of continuity in the Ignition B signal path, which can interrupt spark to the cylinders it controls.
Common causes
Most likely first.
- Open wire between PCM and coil
- Pin pushed back out of connector body
- Cracked solder joint inside the module or sensor
Symptoms
- Check engine light on or flashing
- Rough idle or engine misfire
- Hesitation or reduced power
- Engine may be difficult to start
How to diagnose it
- Review freeze-frame data and misfire counts to see whether the cylinders served by Ignition B are affected when the code sets.
- Use the vehicle wiring diagram to locate Ignition B and inspect its module and coil connectors for loose, corroded, or backed-out terminals.
- Trace the Ignition B signal wire for breaks, chafing, or damage near heat sources and moving parts.
- With the circuit safely isolated as specified by the manufacturer, check continuity along the Ignition B signal path against the manufacturer's specification.
- If the circuit is intact, test the associated coil group and module output using the manufacturer's procedure.
Common fixes
- Reseat a pushed-back terminal in an Ignition B connector.
- Repair an open or damaged Ignition B signal wire.
- Clean or repair corroded Ignition B connections.
- Replace a failed coil in the Ignition B group if testing confirms it.
- Repair or replace the control module only if its Ignition B output fails the manufacturer's tests.
Can I keep driving?
If the check-engine light flashes or the engine runs roughly, stop as soon as it is safe because ongoing misfires can damage the catalytic converter. If the light is steady and the engine runs smoothly, limit driving and avoid hard acceleration until the Ignition B circuit is checked.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.