Ignition Coil H Primary/Secondary Circuit
What it means
The engine computer has detected an electrical fault in the circuit of ignition coil H. This code appears on engines with eight or more cylinders, where coil H usually serves cylinder 8, which should be confirmed in the service manual, and a misfire in that cylinder usually comes with it.
Symptoms4
- Check engine light on, possibly flashing during misfires.
- Shudder at idle and a slight loss of performance.
- A misfire code for the cylinder served by coil H, often P0308.
- Higher fuel consumption.
Possible causes6
- Failed ignition coil H.
- Loose or corroded coil H connector.
- Open or shorted coil H control wire.
- Fault in the shared coil supply or ground.
- Worn spark plug, or oil or water in the plug well.
- Failed driver circuit inside the engine computer (rare).
How to diagnose5
- Identify the cylinder coil H serves from the service manual.
- Inspect the connector, wiring and plug well for oil, water or burn marks.
- Swap coil H with another coil on the same bank, clear the codes and see whether the fault follows it.
- Measure supply and ground and check the control signal at the connector.
- If the fault stays in place, check control wire continuity back to the engine computer.
How to fix5
- Clean the connector and repair loose terminals.
- Repair the damaged control or supply wire.
- Replace ignition coil H if the fault follows it.
- Replace the damaged plug and fix any leak into the plug well.
- 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 low when the connector or wire is at fault, rises when the coil and plug are replaced, 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
The code came with other coil codes. What does it mean?
Several coil codes at once point to a shared cause such as a fuse, relay or coil ground, rather than every coil failing at the same time.
Can I drive a long distance?
It is not advised. Drive gently to the workshop only, because an ongoing misfire in cylinder 8 overheats the catalytic converter and can destroy it.
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.