Quick answer: The P0357 code indicates a circuit malfunction in the ignition coil for cylinder 7, affecting the engine’s ignition system. This issue causes an engine misfire and severe performance loss. It requires prompt attention because driving with an active misfire can quickly overheat and permanently damage your catalytic converter.
If your check engine light has come on alongside a noticeable engine shudder, your vehicle’s computer may have stored code P0357. This code points specifically to a problem in the electrical circuit that controls cylinder 7’s ignition coil. In this guide, we will break down what causes this fault, how to diagnose it step-by-step, and how much repairs typically cost.
What Does P0357 Mean?
The engine control module (ECM) continuously monitors the primary and secondary electrical circuits of each ignition coil. Ignition coil “G” corresponds to cylinder number 7 in the standard diagnostic lettering sequence. When the ECM sends a signal to fire cylinder 7’s coil but detects abnormal voltage or current feedback, it registers code P0357. Without a properly functioning ignition coil, the spark plug cannot ignite the compressed fuel-air mixture, leading to a active cylinder misfire and reduced engine output.
Symptoms
- Illuminated or flashing Check Engine Light
- Engine hesitation, rough idling, or severe shaking under acceleration
- Significant loss of engine power and sluggish throttle response
- Strong smell of unburnt fuel coming from the exhaust pipe
- Engine stalling or dropping revs unexpectedly at stop signs
Possible Causes
Before buying a replacement computer or major engine components, keep in mind that simple connector issues or a worn spark plug cause this code far more often than an expensive internal electronics failure.
- Loose, corroded, or damaged wiring connector at ignition coil 7
- Chafed, melted, or broken wiring harness between the coil and the control module
- Faulty cylinder 7 ignition coil experiencing an internal short or open circuit
- Severely worn, fouled, or improperly gapped spark plug on cylinder 7
- Failed driver circuit inside the Powertrain Control Module (PCM/ECM)
Check These Yourself Before Visiting a Mechanic
- Inspect the connector: Unplug the electrical connector on cylinder 7’s ignition coil. Look for green corrosion, bent copper pins, or cracked plastic locking tabs. Push it back in until it clicks firmly.
- Perform a coil swap test: Move ignition coil 7 to cylinder 5. Clear the fault code with a scanner and start the engine. If the code changes to P0355, the coil unit itself is defective. If P0357 stays active, the fault lies in the wiring harness, spark plug, or ECM.
- Inspect the wire routing: Trace the wire harness leading to coil 7. Check for spots where the loom might be rubbing against hot exhaust manifolds or sharp metal edges.
How to Fix It
- Inspect and repair any visible wiring damage or bad pin contact at the coil 7 electrical harness.
- Swap coils between cylinders to confirm whether the coil electrical circuit or the coil pack itself has failed.
- Inspect the cylinder 7 spark plug for oil contamination, carbon tracking, or damaged ceramic insulation, and replace if worn.
- Use a digital multimeter to verify ground continuity, 12-volt battery power supply, and trigger signal pulses at the coil wiring plug.
- Replace the cylinder 7 ignition coil with a high-quality replacement part if internal coil resistance is out of specification.
- Trace complete circuit continuity to the control module, replacing or reprogramming the ECM if internal ignition driver circuits are damaged.
Estimated Repair Costs (2026)
| Job | Parts ($) | Labor ($) |
|---|---|---|
| Ignition Coil Replacement | $40 – $130 | $50 – $100 |
| Spark Plug Replacement | $10 – $25 | $40 – $80 |
| Wiring Harness Repair | $15 – $35 | $80 – $150 |
| PCM/ECM Replacement | $500 – $1,200 | $150 – $300 |
Note: these are 2026 estimates in US dollars; costs vary by make and model.
Frequently Asked Questions
Can I drive with the P0357 code?
You should avoid driving with an active P0357 code whenever possible. An unburned fuel-air mixture passes directly into the hot exhaust system, which can melt the internal substrate of your catalytic converter within a short distance.
How do I clear the P0357 code?
After completing the necessary repairs, plug an OBD-II scanner into the port beneath your dashboard, turn the ignition key to the ON position without starting the engine, and select ‘Clear/Erase Codes’. You can also complete a few normal drive cycles to allow the PCM to verify the repair and automatically clear the light.
Which cylinder corresponds to Coil G?
In standard diagnostic protocols, Coil ‘G’ represents cylinder 7 in the engine’s firing system (A=1, B=2, C=3, D=4, E=5, F=6, G=7). Always consult your vehicle service manual or firing order diagram to correctly locate cylinder 7 under the hood.