OBD-II Code P0357 — What It Means & How to Fix It

What Does This Error Mean?

P0357 means the PCM detected an electrical fault in the primary circuit of ignition coil G. Coil G serves the 7th cylinder in the ignition firing order. The primary circuit is the low-voltage side that the PCM controls directly. Expect a cylinder misfire, rough running, and possibly a companion misfire code like P0307.

Affected Models

All 1996+ vehicles with 8 or more cylinders and individual coil-on-plug ignition
Common in Ford F-150 and Mustang V8 and V10 engines
Common in GM LS-series and LT-series V8 engines
Common in Dodge/Chrysler Hemi V8 engines
Common in any V8, V10, or V12 engine with individual coils

Common Causes

Failed ignition coil G with an open or short in the primary winding
Damaged, melted, or chafed wiring in the coil G control circuit
Corroded or loose connector at the coil G harness plug
Worn or fouled spark plug in cylinder G overloading and burning out the coil
PCM internal coil driver failure for the coil G output (uncommon but possible)

How to Fix It

Identify which physical cylinder coil G corresponds to on your engine. The letter follows the ignition firing order — coil G is the 7th coil to fire. This may not be the same as cylinder number 7. Check your service manual or a make-specific firing order chart.

Getting the wrong cylinder is the most common error when diagnosing coil codes. Always verify the firing order for your exact engine before pulling any coil.
Inspect the wiring connector at coil G. Look for pushed-back pins, corrosion, melted plastic, or a connector that is not fully seated. Clean the pins with electrical contact cleaner and reseat the connector firmly.

Coils on the rear or passenger-side bank of a V8 are often in tight locations where connectors can vibrate loose or be inadvertently dislodged during other service work.
Perform a coil swap test. Move coil G to a known-good cylinder and place that cylinder's coil where coil G was. Clear all codes and drive. If P0357 goes away and a new coil code appears on the swapped position, coil G is defective.

This is the definitive DIY test for any coil code. It tells you in one test whether the coil is bad or whether the wiring and PCM are at fault.
Inspect and replace the spark plug in the coil G cylinder. A plug that is worn, cracked, or fouled places extra electrical load on the coil and can cause or accelerate coil failure. Replace the plug at the same time as the coil.

A new coil installed on a bad spark plug often fails again within weeks. Replacing both together is the right approach.
Install a new quality coil in the coil G position. Reconnect the harness plug until it clicks. Clear all stored DTCs and perform a test drive with multiple acceleration cycles. Verify no misfire codes return and that P0357 is gone.

Monitor the vehicle for several hundred miles after the repair. A recurring P0357 on a new coil points to a PCM driver issue that needs professional scope testing.

When to Call a Professional

If swapping coil G to another position moves the fault code to that cylinder, the coil itself is bad. If the fault stays on the same cylinder after the swap, the wiring harness or PCM driver needs professional diagnosis. A technician can use an oscilloscope to verify the PCM trigger signal for coil G. Diagnosis typically runs $80-$130. Coil replacement parts cost $25-$80 depending on vehicle make and model.

Frequently Asked Questions

Which cylinder is coil G on my engine?

Coil G is the 7th coil in your engine's ignition firing order. The firing order is a set sequence in which cylinders fire — it is not the same as cylinder numbering. For example, a common GM V8 firing order is 1-8-7-2-6-5-4-3, so the 7th position in that order is cylinder 4. Check your vehicle's service manual for the exact firing order and cylinder layout.

Can I drive with P0357 active?

You can drive short distances at low speeds, but it is not advisable. A misfiring cylinder dumps raw, unburned fuel into the exhaust. This overheats and can permanently damage the catalytic converter. If the check engine light is flashing or blinking, stop driving immediately — that means the misfire is severe enough to cause catalyst damage right now.

How much does fixing P0357 typically cost?

A replacement coil-on-plug coil costs $25-$75 for most common vehicles. Labor is light — usually 30 to 45 minutes. If the wiring harness near coil G is damaged, wiring repair adds $100-$300. PCM driver failures are rare but can push total costs to $600 or more.