What does it mean?
The ignition A control channel has to be pulled low by the module in order to trigger the coil driver. P030C is set when the module commands the channel but continues to read a high voltage on it, meaning the expected current never flows. Electrically this is caused by an open or high resistance path in the control circuit, or by battery voltage being fed onto the line from another circuit. The practical result is the same as a dead channel: the coil is not triggered at the right moment or not at all, so combustion in the cylinders it serves is lost or badly timed, and the misfire monitor normally logs the affected cylinders at the same time.
Symptoms
- Continuous misfire with the MIL on and frequently flashing when the engine is loaded
- Noticeable shaking at idle and poor throttle response
- Hard starting, particularly when the engine is cold or the weather is damp
- Loss of power on hills and when overtaking
- Popping or backfiring from the exhaust and a smell of unburnt fuel
- Higher fuel consumption and, in the long run, catalytic converter damage
Likely causes
- High resistance joint or a partial break in the ignition control wire
- Control circuit shorted to battery voltage through damaged insulation or a wiring error
- Corroded or spread terminals in the coil or module connector reducing contact pressure
- Open igniter input in the coil or ignition module
- Poor ground at the ignition module, so its driver cannot pull the line down
- Faulty module driver stage, checked only after the wiring has been proven good
How to fix it
- Read the misfire counters and the freeze frame data to identify the affected cylinders and the conditions
- Inspect and probe the connectors at the coil and module for terminal tension, corrosion and moisture
- Measure the voltage on the control line with the ignition on and while cranking; a line that never falls indicates the fault
- Perform voltage drop and continuity tests along the control wire, since even a few tenths of a volt point to a bad joint
- Check the ignition module ground and supply, including the relevant fuse and relay
- Look for a short to a permanently live circuit by measuring the control line with the module disconnected
- Repair the harness or renew the coil or module as the tests dictate, then clear the code and confirm over a road test