The P0357 code means the engine control module has detected an electrical malfunction in the primary or secondary circuit for Ignition Coil “G.”
On many coil-on-plug engines, Coil G corresponds to cylinder 7. That assignment isn’t universal, so verify the manufacturer’s coil identification before purchasing parts or dismantling the engine bay.
Common causes include a failed Ignition Coil G, damaged connector terminals, missing power, poor ground, an open or shorted PCM control wire and a failed ignition driver.
P0357 is an electrical circuit code. It isn’t simply another name for a cylinder 7 misfire, and it doesn’t automatically condemn the ignition coil.
P0357 Quick Reference
| Item | Information |
|---|---|
| OBD-II code | P0357 |
| Official description | Ignition Coil “G” Primary/Secondary Circuit Malfunction |
| System | Ignition-coil control |
| Code type | Generic powertrain code |
| Commonly associated cylinder | Cylinder 7, but manufacturer confirmation is required |
| Primary fault | Electrical malfunction affecting Ignition Coil G |
| Severity | High |
| Safe to drive? | Only briefly if the engine runs smoothly |
| Common causes | Failed coil, connector fault, damaged control wire or PCM driver failure |
| Typical repair range | Approximately $75–$2,500+, depending on the cause |
What Does the P0357 Code Mean?
P0357 stands for:
Ignition Coil “G” Primary/Secondary Circuit Malfunction
The powertrain control module commands Ignition Coil G to produce a spark at a precise point in the combustion cycle.
Depending on the ignition-system design, the Coil G circuit may include:
- Ignition fuse
- Ignition or main relay
- Shared coil power supply
- Coil ground
- PCM trigger or control wire
- Ignition-control module
- Primary coil winding
- Secondary coil winding
- Coil boot or spark-plug wire
- Spark plug
- Electrical connectors
- PCM ignition driver
The PCM monitors electrical activity in this circuit while the engine is cranking or running.
P0357 may be stored when the PCM detects:
- Open circuit
- Short to ground
- Short to voltage
- Excessive resistance
- Excessive primary current
- Insufficient primary current
- Missing ignition-driver feedback
- Control voltage that fails to switch
- Primary current that rises or collapses incorrectly
The exact monitoring strategy depends on the manufacturer and ignition-system design.
Which Cylinder Is Ignition Coil G?
Ignition Coil G commonly corresponds to cylinder 7 on engines equipped with one ignition coil per cylinder.
A typical assignment is:
| Coil designation | Common cylinder assignment |
| Coil A | Cylinder 1 |
| Coil B | Cylinder 2 |
| Coil C | Cylinder 3 |
| Coil D | Cylinder 4 |
| Coil E | Cylinder 5 |
| Coil F | Cylinder 6 |
| Coil G | Cylinder 7 |
| Coil H | Cylinder 8 |
This pattern isn’t guaranteed.
Some manufacturers assign letters according to ignition-module channels. Waste-spark systems may use one coil winding to fire two cylinders. Cylinder numbering also differs among V8 engine families.
Confirm Coil G using:
- Manufacturer repair information
- Factory wiring diagram
- Connector pinout
- Component-location diagram
- Cylinder-numbering chart
- Firing order
- Scan-tool cylinder-control test
Don’t identify Coil G by assuming cylinder 7 is on a particular bank or at the rear of the engine. V8 manufacturers have been disagreeing about cylinder numbering for decades and show no signs of reaching peace.
Why Coil G Can Be Difficult to Access
P0357 commonly appears on engines with at least seven individually controlled ignition coils. That usually means a V8, V10 or V12 application.
Coil G may be located:
- Near the firewall
- Beneath an engine cover
- Under an intake tube
- Behind a wiring-harness bracket
- Beside the exhaust manifold
- Beneath cowl components
- Under part of the intake manifold
Rear-cylinder ignition wiring is frequently exposed to:
- Higher underhood temperatures
- Exhaust-manifold heat
- Restricted airflow
- Oil leaks
- Harness tension
- Engine movement
- Difficult previous repairs
Inspect the wiring carefully before replacing the coil. A technician working by feel near the firewall can easily damage a connector lock or pull on the wires instead of the connector body.
What Is the Primary Ignition Circuit?
The primary circuit is the low-voltage side of the ignition coil.
It usually includes:
- Battery-voltage supply
- Ignition fuse
- Relay
- Primary winding
- PCM or ignition-module driver
- Control wire
- Ground circuit
The PCM or ignition module allows current to build through the primary winding. This creates a magnetic field inside the coil.
When the control circuit switches off, the magnetic field collapses and induces high voltage in the secondary winding.
Primary-circuit problems include:
- Missing power
- Open primary winding
- Shorted primary winding
- Open control wire
- Short to ground
- Short to voltage
- Excessive resistance
- Failed PCM driver
What Is the Secondary Ignition Circuit?
The secondary circuit delivers high voltage to the spark plug.
Depending on the system, it may include:
- Secondary coil winding
- Coil tower
- Coil boot
- Spark-plug wire
- Distributor cap and rotor
- Spark plug
- Ground path through the engine
Possible secondary faults include:
- Open secondary winding
- Cracked coil housing
- Carbon tracking
- Damaged coil boot
- Excessive spark-plug gap
- Open spark-plug wire
- Corroded terminal
- Spark leaking to ground
Most modern PCMs don’t measure secondary voltage directly. They may infer secondary operation by monitoring primary current, ignition-driver feedback or changes in crankshaft speed.
How Serious Is the P0357 Code?
P0357 should be considered a high-severity code when Coil G isn’t producing spark.
A dead cylinder may send unburned fuel into the exhaust, where it can overheat and damage the catalytic converter.
Continued driving may cause:
- Catalytic-converter failure
- Oxygen-sensor damage
- Poor fuel economy
- Reduced engine power
- Unsafe acceleration
- Engine stalling
- Fuel contamination of the engine oil
- Damage to the PCM ignition driver
- Secondary ignition damage
Stop driving if:
- The Check Engine Light flashes
- The engine shakes heavily
- Acceleration becomes unsafe
- Raw fuel can be smelled
- The vehicle stalls
- The catalytic converter overheats
- Several cylinders stop firing
- The vehicle becomes difficult to restart
A V8 may disguise one dead cylinder better than a four-cylinder engine. That doesn’t make the misfire harmless. It just means the engine has more coworkers available to cover the shift.
Common P0357 Symptoms
Possible symptoms include:
- Illuminated Check Engine Light
- Flashing Check Engine Light
- Rough idle
- Engine vibration
- Hesitation
- Jerking under acceleration
- Reduced power
- Poor throttle response
- Misfire under load
- Hard starting
- Intermittent stalling
- Poor fuel economy
- Raw-fuel odor
- Backfiring
- P0307 cylinder 7 misfire code
- Reduced-power mode
- No obvious symptoms during an intermittent fault
Some V8 engines may produce only a mild vibration or slight power loss when one cylinder stops firing. Misfire counters and scan data can reveal the problem before it becomes obvious to the driver.
Common Causes of P0357
Possible causes include:
- Failed Ignition Coil G
- Open primary coil winding
- Shorted primary winding
- Internal smart-coil electronics failure
- Loose Coil G connector
- Broken connector lock
- Bent or recessed terminal
- Spread female connector terminal
- Corrosion inside the connector
- Oil contamination
- Water inside the spark-plug well
- Missing Coil G power supply
- Blown ignition-coil fuse
- Failed ignition relay
- Open Coil G control wire
- Control wire shorted to ground
- Control wire shorted to voltage
- Excessive circuit resistance
- Poor Coil G ground
- Poor engine or PCM ground
- Harness damage near the firewall
- Wiring melted near the exhaust manifold
- Harness chafing against the valve cover
- Incorrect replacement ignition coil
- Damaged coil boot
- Excessive spark-plug gap
- Carbon tracking
- Failed ignition-control module
- Damaged PCM connector
- Failed PCM Coil G driver
- PCM software or calibration fault
A worn spark plug may increase secondary voltage demand and eventually damage the coil boot or internal insulation. However, spark-plug problems more commonly produce a misfire code than a direct P0357 circuit fault.
P0357 vs P0307
P0357 and P0307 may appear together, but they report different failures.
| Code | Meaning | Diagnostic focus |
| P0357 | Ignition Coil G primary/secondary circuit malfunction | Coil power, ground, control wiring, electronics and PCM driver |
| P0307 | Cylinder 7 misfire detected | Spark, fuel delivery, compression, airflow and mechanical condition |
The P0307 Cylinder 7 misfire guide covers every major reason cylinder 7 may fail to produce normal combustion.
P0307 may be caused by:
- Worn spark plug
- Weak ignition coil
- Failed fuel injector
- Injector wiring fault
- Intake leak
- Low compression
- Burned valve
- Head-gasket leakage
- Mechanical timing problem
P0357 narrows the investigation toward the electrical circuit for Ignition Coil G.
If both codes appear, diagnose P0357 first. Restoring the Coil G circuit may also eliminate P0307.
If P0307 remains after P0357 is repaired, continue testing fuel delivery, compression and the cylinder’s mechanical condition.
P0357 vs P0350
P0350 identifies a general ignition-coil primary or secondary circuit malfunction without naming one particular coil.
P0357 identifies the circuit associated with Ignition Coil G.
If P0350 appears with several individual coil codes, inspect shared components such as:
- Ignition fuse
- Ignition relay
- Shared power feed
- Engine ground
- PCM ground
- Ignition-control module
- Main harness connectors
If only P0357 is stored, begin with Coil G, its connector and its individual PCM control circuit.
P0357 vs Other Individual Coil Codes
Each P0351–P0362 code applies to a different ignition-coil circuit.
My Pro Street already has dedicated coverage for:
P0357 should remain focused exclusively on the Coil G circuit.
Multiple adjacent coil codes may point toward a shared power feed, common ground, harness connector or PCM problem rather than simultaneous coil failure.
How the Ignition Coil G Circuit Works
A typical coil-on-plug ignition event works as follows:
- The ignition relay supplies battery voltage to Coil G.
- The PCM receives crankshaft and camshaft position signals.
- The PCM calculates ignition timing and coil dwell.
- The PCM sends a trigger signal or directly controls primary current.
- Current builds through the primary winding.
- The control circuit switches off.
- The magnetic field collapses.
- High voltage is induced in the secondary winding.
- Voltage crosses the spark-plug gap.
- Combustion occurs.
The PCM expects predictable voltage and current behavior.
P0357 may be stored if Coil G:
- Draws too much current
- Draws too little current
- Has an open winding
- Has a shorted winding
- Loses power
- Has no trigger signal
- Fails to return driver feedback
- Has a control circuit stuck high or low
How to Diagnose the P0357 Code
1. Scan and Record Every Code
Use a capable scan tool to retrieve:
- Stored codes
- Pending codes
- Permanent codes
- Freeze-frame information
- Cylinder-specific misfire counters
- Battery voltage
- Engine speed
- Engine load
- Coolant temperature
Don’t clear the codes before recording the information.
Freeze-frame data may show whether P0357 occurred:
- During cold startup
- After the engine warmed up
- At idle
- During acceleration
- Under heavy load
- During low battery voltage
- After extended heat soak
2. Check for Related Codes
Look for:
- P0300
- P0307
- P0350
- Other P0351–P0362 codes
- Crankshaft-position codes
- Camshaft-position codes
- System-voltage codes
- Injector-circuit codes
If P0357 appears alone, suspect an individual Coil G circuit problem.
If several coil-circuit codes appeared simultaneously, inspect shared power, relay, fuse and ground circuits before replacing multiple coils.
3. Identify Ignition Coil G
Use manufacturer service information to confirm:
- Coil G location
- Associated cylinder
- Cylinder bank
- Connector pinout
- Power terminal
- Ground terminal
- PCM control terminal
- Feedback circuit, if equipped
On a V8, verify cylinder numbering before removing engine covers or intake components.
4. Inspect Access Around Coil G
Before disconnecting the coil, inspect how the harness is routed.
Look for:
- Harness tension
- Missing retainers
- Wiring trapped beneath a bracket
- Exhaust-manifold proximity
- Oil leaks
- Evidence of previous work
- Connector damage caused by limited access
If components must be removed for access, label connectors and photograph the harness routing before disassembly.
Avoid pulling the coil connector by its wires simply because the rear of the engine has declined to provide room for fingers.
5. Inspect Coil G
Remove Coil G and inspect it for:
- Cracked housing
- Swelling
- Burn marks
- Melted plastic
- Damaged boot
- Carbon tracking
- Corroded spring terminal
- Oil contamination
- Water intrusion
Inspect the spark-plug well.
Oil commonly enters through a leaking valve-cover gasket or tube seal. Repair the leak before installing another coil.
6. Inspect the Coil G Connector
Check the connector for:
- Broken locking tab
- Bent terminals
- Recessed pins
- Spread female terminals
- Corrosion
- Oil contamination
- Water intrusion
- Heat damage
- Improper previous repairs
Perform a terminal-drag test when appropriate.
A loose terminal may open when the engine moves under acceleration or when the harness expands with heat.
7. Inspect the Wiring Harness
Trace the Coil G circuit toward the main harness and PCM.
Pay special attention to wiring near:
- Rear of the cylinder head
- Firewall
- Exhaust manifold
- Valve-cover edge
- Intake-manifold brackets
- Engine mounts
- Harness retainers
Look for:
- Melted insulation
- Chafing
- Pinched sections
- Broken conductors
- Poor splices
- Missing protective loom
- Rodent damage
- Aftermarket wiring
- Harness contact with sharp metal
Move the harness while monitoring Coil G voltage or engine operation.
8. Check Battery and Charging Voltage
Measure battery voltage:
- With the engine off
- During cranking
- At idle
- With electrical accessories operating
- At approximately 2,000 RPM
Low cranking voltage may interfere with ignition operation. Excessive charging voltage may damage smart-coil electronics.
Inspect battery terminals, engine grounds, chassis grounds and PCM grounds.
9. Test Coil G Power
Turn the ignition on and measure voltage at Coil G’s power terminal.
Compare it with:
- Battery voltage
- A known-good ignition coil
- Manufacturer specifications
If Coil G lacks power but other coils have it, inspect its connector, individual power wire and shared splice.
If several coils lack power, inspect the ignition fuse, relay and common feed.
Test the circuit under load. A high-resistance connection may show normal voltage until the coil begins drawing current.
10. Perform Voltage-Drop Testing
Measure voltage drop across:
- Ignition relay contacts
- Coil G power wire
- Fuse-box terminals
- Harness splices
- Connector terminals
- Ground circuits
A damaged wire may pass a continuity test while failing under operating load.
This is especially important when Coil G is at the end of a long shared power circuit or near a heat-damaged harness section.
11. Test Coil G Ground
If Coil G uses a dedicated ground, measure voltage drop between its ground terminal and battery negative while cranking or running the engine.
Compare the result with a known-good coil.
Inspect:
- Coil ground wire
- Ground splice
- Cylinder-head ground
- Engine ground strap
- PCM ground
A poor ground may prevent the internal coil electronics from switching correctly.
12. Test the PCM Control Wire
Use the wiring diagram to identify the Coil G control circuit.
With the PCM and coil disconnected as directed, test for:
- Open circuit
- Short to ground
- Short to voltage
- Excessive resistance
- Short to another coil-control wire
- Correct continuity
Do not use a conventional incandescent test light on the PCM control circuit unless the manufacturer explicitly approves it.
Use an LED test light, logic probe or oscilloscope intended for electronic control circuits.
13. Observe the Coil G Trigger Signal
Back-probe the Coil G control wire without damaging the connector.
Observe the signal during cranking or engine operation.
Compare it with a known-good coil.
Look for:
- Missing trigger pulse
- Signal stuck high
- Signal stuck low
- Incorrect dwell time
- Irregular switching
- Signal disappearing when hot
- Signal changing during a harness wiggle test
If Coil G receives a correct trigger but doesn’t fire, suspect the coil, power, ground or secondary path.
If the trigger is missing, test the control wire and PCM driver.
14. Perform a Coil Swap Test
If the coils are identical and accessible, move Coil G to another cylinder and install a known-good coil in its original location.
Clear the codes and reproduce the original failure conditions.
Possible results include:
- If the fault follows the coil, Coil G is likely defective.
- If P0357 remains at the original circuit, suspect the connector, wiring or PCM driver.
- If the misfire moves but P0357 remains, multiple faults may exist.
A coil swap helps distinguish a failed component from a location-specific electrical fault.
15. Inspect the Spark Plug
Remove the spark plug associated with Coil G.
Check for:
- Excessive electrode wear
- Incorrect gap
- Oil fouling
- Fuel fouling
- Carbon deposits
- Cracked porcelain
- Incorrect heat range
- Loose installation
- Signs of overheating
Excessive spark-plug gap increases secondary voltage demand and may damage the coil boot or internal insulation.
16. Use an Approved Spark Tester
Use an adjustable or manufacturer-approved spark tester to verify Coil G output.
Disable fuel delivery when required and follow the manufacturer’s safety procedures.
Never hold a coil, plug wire or spark plug while cranking. Secondary ignition voltage may exceed 20,000 volts.
Compare Coil G output with a known-good coil under identical conditions.
17. Inspect the Primary Current Ramp
Use an oscilloscope and low-current probe to observe Coil G’s primary current ramp.
Compare it with another coil on the same engine.
Look for:
- No current flow
- Excessive current
- Current rising too slowly
- Current rising too quickly
- Missing current limiting
- Abnormal dwell time
- Premature circuit interruption
- Driver failing to switch
- Shorted primary winding
- Excessive circuit resistance
Current-ramp testing can distinguish coil failure from a weak power circuit or PCM control problem.
18. Test Under Heat
Rear-cylinder coils and connectors may experience substantial heat.
If P0357 appears after the engine warms up:
- Monitor the control waveform from cold.
- Allow the engine to reach operating temperature.
- Continue monitoring during heat soak.
- Perform a hot restart.
- Compare Coil G with a neighboring coil.
A coil, connector or damaged wire may operate normally cold and fail after thermal expansion.
19. Use Resistance Testing Carefully
Some conventional ignition coils have published primary and secondary resistance specifications.
Many modern smart coils don’t.
Integrated electronics may prevent meaningful resistance measurements through the external terminals. Follow vehicle-specific test procedures instead of using generic values.
20. Test the PCM Driver Last
A shorted coil or control wire can damage the PCM’s Coil G driver.
Suspect the PCM only after confirming:
- Correct Coil G power
- Reliable ground
- Known-good coil
- Correct spark plug
- Good control-wire continuity
- No short to ground
- No short to voltage
- Proper connector-terminal tension
- Valid crankshaft and camshaft signals
- Correct ignition-module operation
Repair every external short before installing another PCM. Otherwise, the new module may immediately repeat the original failure.
Common P0357 Diagnostic Mistakes
Avoid these mistakes:
- Assuming Coil G always means cylinder 7
- Guessing the cylinder bank
- Replacing the coil without testing the circuit
- Treating P0357 as identical to P0307
- Ignoring rear-cylinder harness heat
- Pulling the connector by its wires
- Overlooking oil or water in the plug well
- Skipping a terminal-tension test
- Testing voltage without loading the circuit
- Using only a resistance test
- Ignoring the spark plug and coil boot
- Replacing the PCM before checking for a shorted coil
- Driving with a flashing Check Engine Light
How Do You Fix the P0357 Code?
Possible repairs include:
- Reconnecting the Coil G connector
- Replacing damaged connector terminals
- Replacing a broken connector
- Cleaning corrosion
- Removing oil or water contamination
- Repairing a valve-cover or plug-tube seal leak
- Repairing the Coil G power circuit
- Replacing a failed fuse or relay
- Repairing an open control wire
- Repairing a short to ground
- Repairing a short to voltage
- Repairing a poor ground
- Rerouting wiring away from exhaust heat
- Replacing Ignition Coil G
- Replacing a damaged coil boot
- Replacing a worn spark plug
- Replacing a failed ignition-control module
- Repairing PCM connector terminals
- Updating PCM software
- Replacing and programming the PCM when driver failure is confirmed
After repairs:
- Clear the stored codes.
- Start the engine from cold.
- Monitor cylinder misfire counters.
- Verify stable Coil G power.
- Confirm the Coil G trigger signal.
- Allow the engine to reach operating temperature.
- Perform a hot restart.
- Road-test under the freeze-frame conditions.
- Rescan for pending codes.
- Confirm P0357 and P0307 don’t return.
P0357 Repair Costs
| Repair | Estimated cost |
| Diagnostic inspection | $100–$300 |
| Clean or secure connector | $50–$150 |
| Replace Coil G connector | $100–$400 |
| Repair control wiring | $100–$800 |
| Replace ignition fuse or relay | $50–$250 |
| Replace Ignition Coil G | $100–$500 |
| Replace spark plug | $30–$200 |
| Replace complete spark-plug set | $150–$700 |
| Repair plug-tube seal leak | $250–$1,200 |
| Replace ignition-control module | $250–$900 |
| Repair engine wiring harness | $500–$2,500+ |
| PCM software update | $100–$300 |
| Replace and program PCM | $800–$2,500+ |
Costs may increase when rear-cylinder access requires removal of intake, cowl or other engine components.
Can You Drive With a P0357 Code?
Driving isn’t recommended when P0357 causes an active misfire.
A short trip may be possible if:
- The engine runs smoothly
- The Check Engine Light remains steady
- No raw-fuel odor is present
- The vehicle doesn’t stall
- Acceleration remains normal
Stop driving if:
- The Check Engine Light flashes
- The engine shakes heavily
- Power drops substantially
- The vehicle stalls
- Raw fuel can be smelled
- The catalytic converter overheats
- The engine becomes difficult to restart
A V8 may continue running with one failed cylinder, but the catalytic converter still receives unburned fuel. Additional cylinders don’t make the converter more forgiving.
P0357 Frequently Asked Questions
What does code P0357 mean?
P0357 means the PCM has detected an electrical malfunction in the primary or secondary circuit for Ignition Coil G.
Is Ignition Coil G always cylinder 7?
No. Coil G commonly corresponds to cylinder 7, but manufacturers may assign coils differently. Verify the location using service information.
Does P0357 mean Coil G is bad?
Not necessarily. Connector damage, missing power, poor ground, control-wire problems and PCM driver failure can produce the same code.
Is P0357 the same as P0307?
No. P0357 identifies an Ignition Coil G electrical fault. P0307 means cylinder 7 failed to produce normal combustion.
Can a spark plug cause P0357?
An excessively worn or incorrectly gapped plug may stress the coil, but spark-plug problems more commonly cause a P0307 misfire.
Can oil in the spark-plug well cause P0357?
Yes. Oil may damage the coil boot, contaminate the connector and allow secondary ignition voltage to escape to ground.
Can exhaust heat cause P0357?
Yes. Heat may damage Coil G, its connector or nearby wiring, particularly when the coil is near the firewall or exhaust manifold.
Can wiring cause P0357?
Yes. An open control wire, short to ground, short to voltage or loose terminal can trigger P0357 while the coil remains functional.
Can a PCM cause P0357?
Yes, but PCM driver failure is less common than coil, connector and wiring faults. Test the external circuit first.
Can I swap Coil G with another coil?
Yes, if the coils are identical and the manufacturer permits it. If the fault follows the coil, the coil is likely defective. If P0357 remains, test the original circuit.
Will clearing P0357 fix it?
No. Clearing the code only resets the warning temporarily. P0357 will return if the electrical fault remains.
Final Thoughts
P0357 means the PCM has detected an electrical malfunction affecting Ignition Coil G.
Begin by confirming which coil the manufacturer designates as Coil G and which cylinder it serves. Record every code and freeze-frame value before inspecting the coil, connector, plug well and wiring.
Pay particular attention to rear-cylinder harness damage, exhaust heat, terminal tension and wiring strained by limited access.
Verify Coil G power and ground, then compare its control pulse and primary current ramp with a known-good coil. A coil swap can confirm an internal failure, but P0357 remaining at the original circuit points toward the connector, control wire or PCM driver.
Test the PCM last and repair any shorted coil or wiring before installing a replacement module.
For additional diagnostic coverage, visit the complete P-series OBD-II code guide, browse the OBDII Doctor archive or continue with the P0307 Cylinder 7 misfire guide.
P0357 identifies the circuit. Accessing it may still require three extensions, two universal joints and language not approved by the service manual.
