Ignition Coil H Primary Control Circuit Low

What it means

The engine computer fires ignition coil H through a primary control circuit and constantly monitors its voltage. It found the voltage in this circuit lower than expected, which usually means a short to ground or loss of coil power. On most engines with one coil per cylinder, coil H serves cylinder 8, so expect a misfire on that cylinder. This code usually appears only on engines with eight or more cylinders.

Related codes: P2322P0358P0308P0300P2318

Symptoms4

• Engine shaking, usually with a misfire on cylinder 8.
• Loss of power and hesitation on acceleration.
• Check engine light on, possibly flashing during a severe misfire.
• Higher fuel consumption and a smell of unburned fuel from the exhaust.

Possible causes5

• Control wire between the computer and coil H shorted to ground from chafed or melted insulation.
• Internal short in the primary winding of coil H.
• Loss of power to coil H from a blown fuse, failed relay or broken wire in some designs.
• Loose or corroded coil H connector, or oil or water in it.
• Driver circuit fault inside the engine computer (less common).

How to diagnose5

1. Confirm in the service information which cylinder coil H serves on your vehicle, and watch the cylinder 8 misfire counter on a scan tool.
2. Inspect the coil H connector and wiring for torn insulation, rubbing on engine parts or oil contamination.
3. Measure supply voltage at the coil H connector with the key on, and check its fuse and relay.
4. Unplug the connector and check the control wire for a short to ground.
5. Swap coil H with the coil of neighboring cylinder 7; if the code changes to P2318, the coil is faulty.

How to fix5

1. Clean oil and moisture from the connector and reseat it firmly.
2. Replace the failed fuse or relay after confirming there is no short.
3. Repair the grounded control wire and route it away from heat and rubbing points.
4. Replace coil H if the short is inside it, and check the cylinder 8 spark plug at the same time.
5. Clear the codes, then road test and confirm neither the code nor the misfire returns.

Repair cost

In Saudi riyals; the highlighted part is the expected range for this fault.

The cost is low for a connector, fuse or wire, moderate when coil H is replaced, and reaches the upper end in the rare cases where the engine computer needs repair or replacement.

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