P0352: Ignition Coil "B" Primary/Secondary Circuit
The engine control unit has detected a fault in the ignition coil B circuit.
High risk
The engine can misfire and the catalytic converter can overheat. Drive gently and have it checked soon.
Short answer · Can I keep driving with P0352?
Only gently. The engine may misfire and lose power. If the check engine light flashes, avoid acceleration and heavy loads.
What does P0352 mean?
Code P0352 means the coil labelled B did not respond as expected. Check the coil, its connector and the spark plug of that cylinder.
What the car does when the code is set
The check engine light comes on and may flash. The cylinder gets a weak spark or none, so the engine misfires, shakes and loses power. Some engines switch off the injector of that cylinder to protect the catalytic converter.
How the system works
Modern engines usually have one ignition coil per cylinder, mounted on the spark plug. The engine control unit switches the coil primary current on to build a magnetic field and off to release a high-voltage spark. It monitors the primary circuit, and on some engines the secondary side too. A coil that does not respond as expected sets a coil circuit code, labelled A, B, C and so on, often matching the cylinder number.
Common symptoms
Possible causes
Listed without ranking. The cause on your car depends on make, engine and mileage — see the maker notes below.
- Failed ignition coilHeat and age crack the coil insulation or damage the internal winding.
- Wiring or connector faultA loose plug, broken wire or corrosion interrupts the coil circuit.
- Worn spark plugsPlugs with a large gap overload the coil and shorten its life.
- Moisture or oil in the plug wellLeaks from the valve cover gasket can cause arcing and coil failure.
- Engine control unit driver faultLess common, but the output that fires the coil can fail.
How it is diagnosed
- Check for misfire codesA coil circuit fault usually goes with a misfire on the same cylinder.
- Inspect the coil and connectorLook for cracks, burn marks, oil in the plug well and loose or corroded connectors.
- Swap coils between cylindersOn engines with one coil per cylinder, move the suspect coil to another cylinder and see whether the fault follows it.
- Check spark plugsReplace worn plugs when replacing a coil, as worn plugs often caused the coil failure.Ignition systems produce very high voltage; do not touch coils or leads with the engine running.
Questions about P0352
Can a bad spark plug cause a coil code?
It can damage the coil over time. A coil code itself usually points to the coil circuit, but replace worn plugs too.
Should I replace all coils at once?
Not necessarily. Replace the faulty coil and worn plugs. Replacing all coils is sometimes done on older engines where several coils are known to fail, but it is not required.