What it means
Voltage on the primary control of ignition coil B exceeds the calibrated upper limit, indicating an electrical fault that prevents proper coil charging.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Ignition coil B builds its charge through the primary circuit before delivering spark to its assigned plug. The engine control module monitors coil B's primary control signal and sets this code when the signal is higher than expected, often due to an open circuit or a short to battery voltage.
Common causes
Most likely first.
- Primary wire shorted to battery
- Open primary winding
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine light on, possibly flashing
- Engine misfire or rough idle
- Hesitation under acceleration
- Reduced power
How to diagnose it
- Save freeze-frame data and check live misfire counts to see when the cylinder served by coil B is affected.
- Inspect coil B's connector and primary wire for disconnection, broken conductors, corrosion, or damage that could leave the circuit open.
- Check for loose or corroded terminals and make sure coil B's connector is fully seated.
- Using the wiring diagram, test coil B's primary control wire for an open or a short to battery voltage, then test the coil winding to the manufacturer's specification.
- If the coil and wiring pass, check the ECU driver circuit using the manufacturer's diagnostic procedure.
Common fixes
- Reconnect coil B's loose connector or clean and secure its terminals.
- Repair an open primary wire or a short to battery voltage.
- Replace coil B if its primary winding is open.
- Repair the ECU driver circuit if testing confirms it is faulty.
Can I keep driving?
If the check-engine light flashes or the engine misfires heavily, stop driving when safe because continued misfiring can damage the catalytic converter. With a steady light and smooth running, keep any necessary trip short and avoid hard acceleration.
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.