P030D: Ignition B Control Signal Circuit/Open

What does P030D mean?

Ignition B is one of the control signal lines from the engine module to an ignition module, ignition output stage or group of coils; which cylinders it serves is defined by the manufacturer, not by the code standard. The code concerns the logic-level control signal, not the coil's primary current (that has its own codes, P0351 ff and P2300 ff). P030D means the control line is open – the module sees a voltage with its driver off that indicates high resistance. No manufacturer using these codes was found; GM reports coil control faults as P0351 ff (open above 30 kΩ, first trip), so the description follows CARB and that analogy. The affected coils fire wrongly or not at all, causing misfire; many modules then shut off injection to those cylinders to protect the catalyst.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Check engine light on
• Misfire, jerking, rough idle
• Loss of power, possibly cylinders shut off
• Additional misfire codes P0300 ff

Common causes

• High Control line or connector pin open (corrosion, pushed-back pin)
• Medium Ignition module or coil with integrated driver of this group faulty
• Medium Supply or ground of the ignition module faulty
• Low Driver stage in the engine module

Likelihood is a general estimate across vehicles; your make and model may differ.