What Does P0357 Mean?
The ECM has detected a malfunction in the primary or secondary circuit of ignition coil G, which serves cylinder #7 on V8 or larger engines. The coil driver circuit monitoring has identified an abnormal condition such as open circuit, short circuit, or out-of-range current draw. Cylinder 7 will not fire properly, and on a V8 engine the misfire may be partially masked by the other seven cylinders but will still cause rough idle and reduced power.
Common Causes
40%
Failed ignition coil G with internal winding failure, particularly common on high-mileage V8 engines where rear-bank coils see elevated temperatures
25%
Damaged wiring or corroded connector at coil G, especially where the harness routes near the rear exhaust manifold on V8 engines
20%
Worn or fouled spark plug on cylinder 7 causing secondary circuit overload
15%
ECM ignition driver transistor failure for the cylinder 7 output
Diagnostic Steps
1
Swap coil G with a known-good coil from an adjacent cylinder. Clear codes and run the engine. Track whether the fault code follows the coil to its new position.
2
Measure coil G primary (0.4-1.0 ohms) and secondary (6,000-12,000 ohms) resistance. On V8 engines, compare all eight coils to identify any outlier readings.
3
Inspect the coil G connector and harness for heat damage. On V8 trucks, the cylinder 7 coil is often very close to the firewall with limited airflow, accelerating heat-related failures.
4
Check for oil contamination in the spark plug well from leaking valve cover gaskets, which is a common failure pattern on V8 engines with COP ignition.
5
Verify ECM coil G driver signal and power supply. Use a noid light or labscope to confirm trigger pulses are present during cranking.
Estimated Repair Cost
$60 - $350
Parts + labor, varies by vehicle and location
The ECM has detected a malfunction in the primary or secondary circuit of ignition coil G, which serves cylinder #7 on V8 or larger engines. The coil driver circuit monitoring has identified an abnormal condition such as open circuit, short circuit, or out-of-range current draw. Cylinder 7 will not ...
The most common cause of P0357 (Ignition Coil G Primary/Secondary Circuit Malfunction) is: Failed ignition coil G with internal winding failure, particularly common on high-mileage V8 engines where rear-bank coils see elevated temperatures
Typical repair costs for P0357 range from $60 to $350, depending on the vehicle, location, and whether you do it yourself or go to a shop.
A cylinder 7 misfire on a V8 reduces power and fuel economy. Sustained misfire dumps raw fuel into the catalytic converter, risking overheating and potential exhaust system fire.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0357 to identify the root cause.
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Quick Info
Category
Powertrain
System
Ignition System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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