Ignition Coil B Primary/Secondary Circuit
What it means
The engine computer has detected an electrical fault in the circuit of ignition coil B. On most coil-on-plug engines coil B serves cylinder 2, although some manufacturers map it differently, and the result is usually a misfire in that cylinder.
Symptoms4
- Check engine light on, possibly flashing during misfires.
- Noticeable shaking at idle and hesitation on acceleration.
- A misfire code for the cylinder served by coil B, often P0302.
- Higher fuel consumption.
Possible causes6
- Failed ignition coil B.
- Loose or corroded coil B connector.
- Open or shorted control wire between coil B and the engine computer.
- Fault in the shared coil supply, such as a fuse or relay.
- Worn spark plug or cracked boot in the same cylinder.
- Failed driver circuit inside the engine computer (rare).
How to diagnose5
- Confirm which cylinder coil B serves from the service manual.
- Inspect the coil B connector and wiring.
- Swap coil B with another cylinder's coil and clear the codes; if the code changes to the other coil or the misfire follows it, coil B is faulty.
- Measure supply and ground at the connector and check the control pulses from the computer.
- Inspect the spark plug in the same cylinder for wear or tracking marks.
How to fix5
- Clean the connector and repair loose terminals.
- Repair the damaged control or supply wire.
- Replace ignition coil B if the swap test confirms it is faulty.
- Replace a worn spark plug in the same cylinder.
- Clear the codes, road test and confirm the code does not return.
Repair cost
In Saudi riyals; the highlighted part is the expected range for this fault.
The cost is small for a connector or wire repair, rises when the coil and plug are replaced together, and rarely goes beyond this range if the engine computer has failed.
Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026
Frequently asked questions
How does this code relate to P0302?
P0352 means the computer saw an electrical fault in the coil B circuit, while P0302 means a misfire in cylinder 2. Seeing both together suggests the coil or its wiring is causing the misfire.
Should I replace all the coils?
No. Replace coil B only if it is proven faulty, unless all coils are old and failing repeatedly, in which case replacing them together may be economical.
Was this explanation helpful?
Tap the stars to rate; you can change it later.
What was wrong? (optional)
This guide is for information only and does not replace an inspection by a qualified technician. If the fault involves brakes, steering, engine temperature, electrics or refrigerant, do not attempt the repair yourself.
Report a mistake
Spotted something inaccurate? Tell us and we will review and correct it.
Report received — thank you
This is your private tracking link. It shows the status and our reply as soon as it is posted.
The link is saved in this browser only.