OBD-II Code P0355 — What It Means & How to Fix It

What Does This Error Mean?

P0355 means the PCM detected an electrical fault in the primary circuit of ignition coil E. Coil E typically refers to the coil serving the 5th cylinder in the firing order. The primary circuit is the low-voltage side that the PCM directly controls. You will likely experience a misfire on that cylinder, rough idle, and reduced power.

Affected Models

All 1996+ vehicles with individual coil-on-plug or coil-near-plug ignition
Common in Ford and Lincoln V8 and V10 engines
Common in GM LS-series V8 engines
Common in Dodge/Chrysler Hemi V8 engines
Common in Toyota and Lexus V8 engines

Common Causes

Failed ignition coil E with an open or short in the primary winding
Damaged or melted wiring in the coil E primary control circuit
Corroded or loose connector at the coil E harness plug
Failed PCM coil driver circuit for coil E (uncommon but possible)
Spark plug in the affected cylinder has failed and is overloading the coil

How to Fix It

Identify which cylinder coil E corresponds to on your specific engine. On most vehicles the coil letter designation follows the firing order, not the physical cylinder number. Check a service manual or model-specific forum to confirm the cylinder before working.

Getting the wrong coil is a common mistake because coil letter designations (A, B, C, D, E...) do not always match cylinder numbers (1, 2, 3, 4, 5...).
Inspect the coil E connector for corrosion, damage, or loose fit. Unplug it and check all pins inside the connector. Spray with electrical contact cleaner, allow to dry, and reconnect firmly. Check the wiring back toward the PCM for any visible damage.

Connector problems are a common cause of primary circuit codes. A loose connection causes intermittent misfires that worsen over time.
Swap coil E with an identical coil from a non-misfiring cylinder. Clear all fault codes and drive the vehicle. If the fault code moves to the cylinder that received coil E, the coil is confirmed defective and needs replacement.

Only swap identical coils. Coils from different cylinder positions may look similar but have different internal specifications on some engines.
Replace the spark plug in the affected cylinder at the same time as the coil if it has not been done recently. A failing spark plug can overload and destroy a coil. Installing a new coil on a bad plug often results in premature coil failure.

On high-mileage engines, replace all spark plugs as a set when you change a coil. This prevents the remaining old plugs from stressing the new coil.
Replace coil E with a quality coil. Clear all stored fault codes and perform a test drive to confirm the misfire is gone and P0355 does not return. Monitor the vehicle over several drive cycles.

Use OEM or OEM-equivalent quality coils. Cheap aftermarket coils often fail prematurely and may produce weak sparks even when new.

When to Call a Professional

If swapping the coil does not move the fault code to a new cylinder, the wiring or PCM driver is at fault. A technician can check the PCM-side coil trigger signal with an oscilloscope. Diagnosis typically runs $80-$130. Coil replacement costs $30-$80 per coil; labor varies by engine access.

Frequently Asked Questions

What is the primary circuit of an ignition coil?

The ignition coil has two sides — primary and secondary. The primary side is the low-voltage circuit. The PCM sends a 12-volt control signal to trigger the coil. The secondary side produces the high-voltage spark that fires the plug. P0355 is a problem on the low-voltage primary side.

Will P0355 always cause a misfire?

Almost always. If the primary circuit is open or shorted, the coil cannot create a spark. No spark means that cylinder misfires on every firing event. You will likely see a companion misfire code alongside P0355. In rare cases of intermittent faults, the misfire may only occur occasionally.

Can I replace just the one coil or do I need to replace them all?

You can replace just the one faulty coil. However, on high-mileage engines all the coils have similar wear. Many mechanics recommend replacing all coils at the same time to prevent future breakdowns. At minimum, inspect and test the other coils while you have access.