P0357 — Ignition Coil “G” Primary/Secondary Circuit #

Note: The description of this Diagnostic Trouble Code (DTC) may vary depending on the vehicle manufacturer (OEM). Always refer to your vehicle’s service manual for the most accurate definition.

• Ignition Coil ‘G’ Primary/Secondary Circuit Malfunction (Toyota, Lexus)
• Ignition Coil G Primary/Secondary Circuit Fault (Ford, Lincoln)
• Ignition Coil G Circuit Error (Chrysler, Dodge, Jeep)
• Ignition Coil 7 Primary/Secondary Circuit (General Motors, Chevrolet, GMC, Cadillac)

Code P0357 Summary #

P0357 is a generic OBD-II trouble code indicating a malfunction in the ignition coil “G” primary or secondary circuit. The ignition coil is a component that transforms the battery’s low voltage into the high voltage needed for the spark plug to ignite the air-fuel mixture inside the engine. In most vehicles, coil “G” refers to the seventh ignition coil in the firing order. If the Powertrain Control Module (PCM) detects an abnormal voltage or signal in the coil “G” circuit—whether due to an open, short, or resistance outside of specifications—it will trigger the P0357 code. This fault may lead to engine misfires, rough operation, or even prevent the engine from starting.

Common Symptoms for Code P0357 #

When P0357 is present, the vehicle will often display obvious signs of ignition trouble. These symptoms may range from subtle changes in engine performance to more drastic drivability issues. If you are experiencing any of the following, P0357 could be the culprit:

• Check Engine Light illuminated
• Engine misfire, especially on one cylinder
• Rough idle or engine shaking
• Reduced power or hesitation during acceleration
• Poor fuel economy
• Hard starting or occasional no-start condition
• Potential increase in exhaust emissions

Probable Causes for Code P0357 #

Several factors may trigger P0357. Statistically, some causes are more common than others. Understanding these causes helps prioritize your diagnostic approach:

1. Faulty ignition coil “G” (most common)
2. Damaged or corroded coil wiring/connectors
3. Open or shorted circuit in the coil harness
4. Faulty Powertrain Control Module (PCM) (less common)
5. Defective spark plug (rare, but possible if coil and wiring are good)

Step-by-Step Diagnosis for Code P0357 #

Diagnosing P0357 requires a systematic approach to pinpoint the source of the fault. Following these steps will help avoid unnecessary parts replacement and ensure a precise repair:

• 1. Confirm the code: Use a scan tool to verify P0357 is present and note any related codes (especially misfire codes for cylinder 7).
• 2. Visual inspection: Check the ignition coil “G” and its connector for visible damage, corrosion, or loose connections.
• 3. Swap test: Swap coil “G” with another cylinder’s coil. Clear the code and monitor if the code moves to the new cylinder (e.g., P0355 if moved to coil E).
• 4. Check wiring harness: Inspect the coil wiring between the coil and PCM for continuity, shorts to ground, or open circuits using a multimeter.
• 5. Test the ignition coil: Use an ohmmeter to check the coil’s primary and secondary resistance against OEM specifications.
• 6. Check spark plug: Inspect and, if needed, test or replace the spark plug associated with cylinder 7.
• 7. PCM diagnosis: If all else checks out, consult OEM service procedures to test the PCM’s coil driver circuit (rare failure point).

Possible Repairs for Code P0357 #

Once the root cause is found, apply the appropriate repair. The following solutions address the most common causes of P0357:

• Replace the faulty ignition coil “G”
• Repair or replace damaged ignition coil wiring or connector
• Repair open/shorted circuits in the coil harness
• Replace the spark plug if it is fouled or defective
• Replace or reprogram the PCM (only after confirming all other components and wiring are in good condition)

Can You Still Drive with Code P0357? #

Driving with code P0357 is generally not recommended. While the vehicle may still run, a faulty ignition coil can lead to severe engine misfires, which in turn may cause damage to the catalytic converter (due to unburned fuel), poor performance, increased emissions, and potential safety concerns. It’s best to address the issue as soon as possible to avoid further complications or costly repairs.

Vehicles Most Commonly Affected by Code P0357 #

P0357 is most frequently reported on vehicles equipped with individual coil-on-plug ignition systems—especially those with V6 or V8 engines. While it is a generic code, certain makes and models see it more often due to design and component placement:

• Ford F-150, Explorer, Mustang (modular V8 engines)
• Toyota Camry, Tacoma, Tundra (V6 and V8 engines)
• Chevrolet Silverado, GMC Sierra (LS V8 engines)
• Dodge Ram, Jeep Grand Cherokee (Hemi V8 engines)
• Lexus LS, GS series (V8 engines)

Common Mistakes & Best Practices for Code P0357 #

Misdiagnosis is common when troubleshooting ignition coil codes. Following best practices ensures an efficient and accurate repair:

• Replacing the ignition coil without inspecting the connector or wiring
• Not swapping coils to confirm the fault follows the component
• Ignoring related misfire or multiple DTCs
• Overlooking PCM software updates or TSBs (Technical Service Bulletins) from the OEM
• Using non-OEM or low-quality replacement coils (may lead to recurrent issues)

Quick FAQ for Code P0357 #

Still have questions? Here are quick answers to the most common concerns:

• Q: Can a bad spark plug cause P0357?
  A: While rare, a severely fouled or shorted spark plug can occasionally trigger the code, but the majority of cases are due to coil or wiring faults.
• Q: How much does it cost to fix P0357?
  A: Costs vary by vehicle and repair, but replacing a single ignition coil typically ranges from $75 to $250 (parts and labor), while wiring or PCM repairs may cost more.