P0357 Code: Ignition Coil G Primary Circuit Open
P0357 Code: The “G” Usually Points to Coil 7 — Verify the Map First
P0357 is a primary control-circuit fault, not proof of a bad spark plug or PCM. Coil lettering and cylinder numbering must be confirmed for the engine.
P0357 = Ignition Coil G Primary Control Circuit/Open. P0357 means the ignition coil G primary control circuit is open or not responding correctly. G often maps to cylinder 7, but verify service information, then test coil power, connector and driver control.
What Does P0357 Actually Mean?
P0357 is the generic code for ignition coil G primary control circuit/open. On many engines G corresponds to cylinder 7, but cylinder and coil mapping must be checked by VIN.
The primary circuit includes the fused power feed, coil winding, connector, control wire and PCM driver. A secondary ignition problem can cause a misfire, but P0357 specifically directs attention to primary control monitoring.
Always use the service information for the exact VIN; thresholds and test sequences differ by manufacturer.
Symptoms of P0357
Flashing means catalyst-damaging misfire.
The affected cylinder may not fire.
Most noticeable under load.
Unburned fuel reaches the exhaust.
Possible on engines with multiple coil faults.
Supports cylinder 7 combustion loss when G maps there.
What Causes P0357? (Ranked Cheapest First)
The labels and order below are diagnostic weightings for test sequence, not published failure-rate statistics. Vehicle design, mileage and companion codes can change the ranking.
Loose, corroded or broken coil connector (25% diagnostic weighting)
Heat and service movement damage terminal tension.
How to prove it: Inspect and perform a connector wiggle test on misfire data.
$10-$250Failed ignition coil G (25% diagnostic weighting)
The primary winding or internal electronics opens.
How to prove it: Swap with an identical coil and test primary control.
$40-$180Shared power-feed or fuse fault (15% diagnostic weighting)
One or several coils lose B+ under load.
How to prove it: Measure loaded voltage at the coil.
$5-$350Open control wire to PCM (15% diagnostic weighting)
Harness chafe interrupts the driver path.
How to prove it: Load-test the circuit end to end.
$20-$600Spark plug or boot problem (10% diagnostic weighting)
High secondary demand can damage or confuse coil operation.
How to prove it: Inspect plug gap, carbon tracking and boot.
$10-$250PCM driver fault (10% diagnostic weighting)
Possible after a shorted coil but not the first assumption.
How to prove it: Verify the control wire and coil before pin-level PCM tests.
$700-$2,500What You'll Need
Diagnostic tools
- Full-system scan tool with live data and active tests
- Digital multimeter with back-probes
- Fused jumper leads
- Vehicle wiring diagram and connector views
- Test light or low-current probe where approved
Possible parts and supplies
- Connector cleaner and terminal tools
- Automotive wire and sealed splices
- Correct fuse or relay after testing
- Replacement component only if the circuit proves it faulty
iCarzone UR1000 Bidirectional Scan Tool with ECU Coding
Use the UR1000 to save P0357 freeze-frame data, scan companion modules, graph the relevant command and feedback, and run supported active tests. Confirm electrical values with a meter before replacing parts.
How to Diagnose P0357 at Home
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1
Save the complete scan report
Record P0357, status, freeze-frame values and every companion code before clearing memory. The companion code often identifies the affected side or prerequisite failure.
- Scan all modules, not only the engine controller.
- Record battery voltage and operating conditions.
- Note recent repairs, low-voltage events and intermittent symptoms.
- Do not erase evidence before duplicating the fault.
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2
Confirm the exact component and layout
Confirm cylinder numbering and coil G assignment. Identify shared coil power and the individual PCM control wire before swapping any coils.
- Use the VIN-specific wiring diagram and component locator.
- Verify bank, sensor, solenoid or circuit labels before unplugging anything.
- Inspect nearby heat, fluid and collision damage.
- Check connectors for water, corrosion, spread terminals and poor locks.
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3
Check the inexpensive basics
Inspect the coil connector, lock, oil or water in the plug well and the shared ignition fuse. Check the spark plug gap because excessive secondary demand can stress a coil.
- Verify battery and charging voltage are stable.
- Inspect related fuses, grounds, hoses, fluid or mechanical linkages.
- Repair obvious damage before condemning an electronic part.
- Re-scan after restoring any shared power or ground fault.
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4
Use live data or an active test
Graph cylinder-specific misfire counts and coil control data if supported. Move the coil only when identical and track whether the misfire follows; the circuit code may remain at the original cylinder.
- Graph the relevant command and feedback PIDs together.
- Change one condition at a time and watch for a plausible response.
- Run a supported output test only when the vehicle is safe and stationary.
- Compare left/right or bank-to-bank data when the design permits.
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5
Prove the circuit or system under load
Verify loaded B+ and ground, then observe the control pulse with an approved scope or test method. Never short the driver with a conventional test light.
- Back-probe without spreading terminals.
- Use voltage-drop or current testing instead of an unloaded continuity check.
- Follow the factory limits for the exact module and component.
- Replace the part only when power, ground, command and response point to it.
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6
Repair, reset and verify
Repair the terminal, wire or coil, install a correctly gapped plug if needed, then load-test the engine and confirm no misfire or coil circuit code returns.
- Clear codes only after the repair is complete.
- Perform any required relearn, adaptation or bleed procedure.
- Repeat the original enable conditions while logging data.
- Confirm P0357 and the companion codes do not return.
Safety: Ignition systems generate high voltage. Do not hold a coil or spark tester while cranking, and do not probe a PCM driver with an incandescent test light.
How Much Does P0357 Cost to Fix?
| Repair | DIY Cost | Shop Cost | Notes | Type |
|---|---|---|---|---|
| Connector clean or terminal repair | $0-$40 | $80-$220 | Inspect first | DIY/Inspect |
| Fuse or relay | $8-$60 | $90-$250 | Test before replacing | DIY/Inspect |
| Harness repair | $15-$100 | $150-$650 | Depends on access | DIY/Inspect |
| Sensor, switch or solenoid | $25-$250 | $180-$650 | Code-specific part | DIY/Inspect |
| Module software update | N/A | $0-$250 | VIN-specific | Shop |
| Control module replacement/programming | N/A | $700-$2,500 | Last resort | Shop |
Prices are broad U.S. estimates for July 2026. Labor rate, access and parts availability can move the final bill substantially.
Which Vehicles Commonly Report P0357?
| Make / Model | Years | Powertrain | Diagnostic Notes | Focus |
|---|---|---|---|---|
| Domestic cars and light trucks | Varies by model | coil-on-plug ignition | Confirm the ignition coil G primary circuit layout and code enable criteria by VIN. | High |
| European vehicles | Varies by model | coil-on-plug ignition | Factory code text may add a manufacturer-specific suffix or test threshold. | Medium |
| Asian vehicles | Varies by model | coil-on-plug ignition | Connector pinout and active-test support differ by platform. | Medium |
| Hybrids or electrified variants | When equipped | coil-on-plug ignition | Do not assume the non-hybrid test plan applies to high-voltage hardware. | Lower |
| Older high-mileage vehicles | Age dependent | coil-on-plug ignition | Corrosion, fluid intrusion and harness fatigue deserve extra attention. | Medium |
| Recently repaired vehicles | Any year | coil-on-plug ignition | Recheck disturbed connectors, grounds, hoses and software history first. | High |
Why G often means cylinder 7
Generic lettering follows the firing-cylinder designation on many engines, but manufacturers can package or label coils differently. The firing order is not a substitute for the component map.
When a coil swap helps
If the misfire moves with the coil, the coil is suspect. If P0357 and the original cylinder remain, focus on that connector, power and control circuit.
Should You DIY or Call a Mechanic?
- ✓ The vehicle remains safe and stable while testing.
- ✓ You can identify the correct component from a wiring diagram.
- ✓ The checks are limited to accessible connectors, hoses, fuses or live data.
- ✓ No programming, high-voltage work or internal mechanical repair is required.
- → The vehicle stalls, overheats, misfires severely or enters a harsh limp mode.
- → High voltage, fuel pressure or internal transmission work is involved.
- → The circuit reaches an inaccessible module connector.
- → Programming, oscilloscope work or manufacturer tooling is required.
Frequently Asked Questions
What does P0357 mean?
Can I drive with P0357?
What is the most common first check for P0357?
Does P0357 always mean the ignition coil G primary circuit is bad?
How does the iCarzone UR1000 help?
Should I clear P0357 first?
Can a weak battery create this code?
How do I confirm the repair?
This article is for informational purposes only. Always follow the factory service manual, safety procedures and local emissions rules for the exact vehicle. iCARZONE is not responsible for damage caused by improper diagnosis or repair.