What it means
Ignition A Control Signal Circuit Low: the signal voltage is below the expected range. This line drives an ignition coil group; a fault causes misfire on those cylinders.
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 uses the Ignition A control signal circuit to command an ignition coil or coil group, with the exact assignment set by the vehicle's wiring. P030B sets when the signal is detected below its expected electrical range, which can occur with a short to ground or a poor, resistive connection.
Common causes
Most likely first.
- Short to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
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 identify whether cylinders served by Ignition A lose ignition when the code sets.
- Identify the Ignition A signal wire from the vehicle wiring diagram and inspect it and its connectors for chafing, corrosion, moisture, or loose terminals.
- Check whether the signal wire is shorted to ground, following the manufacturer's isolation and test procedure.
- Measure the Ignition A signal at the relevant connector under the specified test conditions and compare it with the manufacturer's specification.
- If the wiring and connections pass, test the coil group and control-module output using the manufacturer's procedure.
Common fixes
- Repair chafed insulation or a signal wire shorted to ground in the Ignition A circuit.
- Clean or repair corroded Ignition A terminals and connectors.
- Restore proper terminal fit where a connection has high resistance.
- Replace a faulty Ignition A coil or coil group if testing identifies it.
- Repair or replace the control module only if its signal output fails the manufacturer's tests.
Can I keep driving?
A flashing check-engine light or pronounced misfire calls for stopping as soon as it is safe, since continued misfiring can damage the catalytic converter. If the light is steady and the engine runs evenly, limit driving and avoid hard acceleration until the low signal is diagnosed.
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.