If your OBD-II scanner displays P0355, your vehicle’s Engine Control Module (ECM) or Powertrain Control Module (PCM) has detected a malfunction in the Ignition Coil “E” Primary/Secondary Circuit.
The generic OBD-II definition for P0355 is:
Ignition Coil “E” Primary/Secondary Circuit Malfunction
On many vehicles, Ignition Coil “E” refers to the ignition coil serving Cylinder 5, although coil lettering can vary by manufacturer. The PCM continuously monitors the ignition coil circuit to verify that it receives proper voltage, ground, and switching commands.
When the PCM detects an open circuit, short circuit, abnormal current draw, missing control pulse, or improper coil response, it stores P0355 and illuminates the Check Engine Light.
The ignition system is responsible for:
- Producing high-voltage spark
- Igniting the air/fuel mixture
- Maintaining engine performance
- Supporting fuel economy
- Controlling emissions
- Preventing engine misfires
- Protecting the catalytic converter
Common causes include:
- Failed ignition coil
- Damaged ignition coil connector
- Broken or shorted wiring
- Corroded electrical terminals
- Worn or incorrectly gapped spark plug
- Damaged ignition coil boot
- Oil or moisture inside the spark plug well
- PCM ignition driver failure (rare)
Because an ignition fault can produce severe misfires and catalytic converter damage, P0355 should be diagnosed and repaired promptly.
What Does the P0355 Code Mean?
The ignition coil converts battery voltage into the high voltage needed to create a spark inside the combustion chamber.
The PCM controls the coil’s primary circuit by rapidly switching it on and off. When the magnetic field inside the coil collapses, the secondary winding generates enough voltage to fire the spark plug.
If the PCM detects that the Ignition Coil “E” circuit is:
- Open
- Shorted to power
- Shorted to ground
- Drawing excessive current
- Failing to respond correctly
it stores P0355.
Unlike P0305, which indicates that Cylinder 5 is misfiring, P0355 specifically identifies an electrical malfunction affecting the Ignition Coil “E” circuit.
What Is an Ignition Coil?
Most modern engines use a Coil-on-Plug (COP) ignition system, where each cylinder has an individual ignition coil installed directly above the spark plug.
A typical ignition coil contains:
- Primary winding
- Secondary winding
- Iron core
- Internal switching electronics on some designs
- Electrical connector
- Rubber spark plug boot
- High-voltage spring or terminal
The coil converts approximately 12 volts into 20,000 to 60,000 volts, depending on engine design and operating conditions.
That voltage must be strong enough to jump the spark plug gap under cylinder compression.
Why Ignition Coil “E” Is Important
Ignition Coil “E” directly affects combustion in its assigned cylinder, commonly Cylinder 5.
Proper operation supports:
- Smooth engine idle
- Reliable starting
- Full engine power
- Proper throttle response
- Fuel efficiency
- Low exhaust emissions
- Catalytic converter protection
If the coil circuit fails, the affected cylinder may misfire intermittently or stop firing completely.
How the PCM Detects P0355
The PCM monitors several ignition-related values, including:
- Coil primary circuit voltage
- Coil current draw
- Ignition driver feedback
- Engine RPM
- Crankshaft acceleration
- Misfire counters
- Ignition timing
- Injector activity
If the PCM commands Ignition Coil “E” but does not detect the expected response, it stores P0355.
On some vehicles, the PCM may disable fuel injection to the affected cylinder to protect the catalytic converter from unburned fuel.
What Does “Primary/Secondary Circuit Malfunction” Mean?
P0355 does not automatically mean the ignition coil itself has failed.
The code means a problem exists somewhere in the ignition coil’s electrical path.
The primary side includes:
- Battery voltage supply
- PCM switching circuit
- Coil primary winding
- Wiring and connector
The secondary side includes:
- Coil secondary winding
- Coil boot
- High-voltage terminal
- Spark plug
Possible causes include:
- Failed coil winding
- Open wiring
- Shorted control circuit
- Loose connector
- Corroded terminals
- Excessive spark plug resistance
- Carbon tracking
- PCM driver failure
Proper testing is required before replacing parts.
Can a Bad Ignition Coil Cause P0355?
Absolutely.
A failed ignition coil is one of the most common causes of P0355.
Typical coil failures include:
- Internal primary winding failure
- Internal secondary winding failure
- Heat-related breakdown
- Cracked insulation
- Internal short circuit
- Moisture intrusion
- Burned terminals
A coil may operate normally at idle but fail under acceleration when spark demand increases.
Can a Bad Spark Plug Cause P0355?
Yes.
A worn or damaged spark plug may force the ignition coil to generate higher voltage than normal.
Common spark plug problems include:
- Excessive electrode gap
- Oil fouling
- Fuel fouling
- Carbon deposits
- Cracked ceramic insulator
- Incorrect heat range
- Incorrect replacement plug
The increased voltage demand may overheat the coil or expose weak insulation.
Replacing the coil while ignoring the worn plug is a fine way to buy the same part twice.
Can Wiring Problems Cause P0355?
Definitely.
Inspect the ignition coil circuit for:
- Broken wires
- Chafed insulation
- Heat damage
- Loose connector pins
- Corrosion
- Rodent damage
- Poor previous repairs
- Oil contamination
Ignition wiring is exposed to heat, vibration, oil, and repeated service work, so harness damage is common.
Can Oil in the Spark Plug Well Cause P0355?
Yes.
Oil can enter the spark plug well through failed:
- Valve cover gaskets
- Spark plug tube seals
- Camshaft cover seals
Oil contamination may damage:
- Coil boot
- Electrical connector
- Spark plug insulator
- Coil housing
The leak must be repaired before installing new ignition components.
Can Moisture Cause P0355?
Yes.
Moisture inside the spark plug well may cause:
- Spark leakage
- Carbon tracking
- Coil boot breakdown
- Intermittent misfires
- Corroded terminals
This can occur after:
- Engine washing
- Heavy rain
- Coolant leaks
- Damaged weather seals
Can a PCM Problem Cause P0355?
Yes, but PCM failure is rare.
The PCM contains a driver circuit that controls the ignition coil.
A failed driver may cause:
- No switching signal
- Constant voltage
- Intermittent coil operation
- Immediate return of P0355
The PCM should only be suspected after verifying:
- Ignition coil
- Spark plug
- Wiring
- Connector
- Voltage supply
- Ground circuit
The PCM is the final suspect, not the first part launched from the parts cannon.
P0355 Quick Facts
| Item | Information |
|---|---|
| DTC | P0355 |
| Generic Definition | Ignition Coil “E” Primary/Secondary Circuit Malfunction |
| System | Ignition / Engine Management |
| Typical Coil Assignment | Cylinder 5 on many vehicles |
| Severity | High |
| Safe to Drive? | Limited driving only |
| Common Symptoms | Check Engine Light, rough idle, misfire, hesitation, reduced power |
| Common Causes | Failed coil, worn spark plug, wiring damage, connector problems |
| Typical Repair Cost | $100–700+ |
| Related Codes | P0305, P0351, P0352, P0353, P0354, P0356 |
Common Symptoms of P0355
Drivers may experience:
- Check Engine Light
- Flashing Check Engine Light
- Rough idle
- Cylinder 5 misfire
- Engine shaking
- Hesitation
- Poor acceleration
- Reduced fuel economy
- Hard starting
- Engine stalling
- Strong fuel odor
- Reduced engine power
Symptoms may be constant or intermittent depending on the failure.
Common Vehicles That Experience P0355
P0355 can appear on nearly any OBD-II vehicle using individual ignition coils, including:
- Chevrolet
- GMC
- Cadillac
- Buick
- Ford
- Lincoln
- Dodge
- Chrysler
- Jeep
- Ram
- Toyota
- Lexus
- Honda
- Acura
- Nissan
- Infiniti
- Hyundai
- Kia
- Subaru
- Mazda
- Volkswagen
- Audi
It is especially common on:
- High-mileage engines
- V6 and V8 engines
- Coil-on-plug ignition systems
- Turbocharged engines
- Vehicles with overdue spark plug maintenance
- Engines with valve cover gasket leaks
- Vehicles exposed to high underhood temperatures
What Does P0355 Really Mean?
Many drivers assume P0355 means:
“Replace the Cylinder 5 ignition coil.”
That may be correct, but the code actually means:
“The PCM detected an electrical malfunction in the Ignition Coil ‘E’ primary or secondary circuit. Inspect the coil, spark plug, connector, wiring, voltage supply, ground, and PCM control circuit before replacing parts.”
The underlying fault may involve:
- Ignition Coil “E”
- Spark plug
- Coil boot
- Wiring harness
- Electrical connector
- Battery voltage supply
- Engine ground
- PCM driver circuit
- Oil or moisture contamination
A complete diagnosis should evaluate the entire circuit rather than assuming the coil is guilty because it was standing nearby.
Common P0355 Scan Tool Patterns
Using a professional scan tool is one of the fastest ways to diagnose P0355.
Because the PCM continuously monitors Ignition Coil “E,” live scan data can quickly determine whether the fault is caused by the ignition coil, spark plug, wiring, electrical connector, or PCM driver circuit.
Modern scan tools may display:
- Cylinder misfire counters
- Engine RPM
- Ignition timing
- Coil command status
- Short-Term Fuel Trim (STFT)
- Long-Term Fuel Trim (LTFT)
- Crankshaft speed variation
- Cylinder contribution
- Freeze-frame data
On many vehicles, Ignition Coil “E” corresponds to Cylinder 5, although the actual coil assignment should always be verified using factory service information.
Pattern 1: P0355 With Cylinder 5 Misfire
One of the most common scan-tool patterns is:
- P0355 stored
- P0305 stored
- Cylinder 5 misfire counter increasing
- Rough engine idle
Possible causes include:
- Failed Ignition Coil “E”
- Worn spark plug
- Damaged coil connector
- Broken wiring
- Oil contamination
This is the most common real-world scenario associated with P0355.
Pattern 2: P0355 Without a Misfire Code
Some vehicles may display:
- Check Engine Light
- P0355 stored
- Engine runs normally
- No noticeable drivability issues
Possible causes include:
- Intermittent ignition coil failure
- Connector corrosion
- Wiring beginning to fail
- PCM detecting an electrical fault before combustion is affected
Early diagnosis often prevents larger ignition system failures.
Pattern 3: Misfire Only Under Load
Live data may show:
- Smooth idle
- Misfire during acceleration
- High engine load
- Cylinder 5 misfire counter increasing
- P0355 returning under heavy throttle
Possible causes include:
- Weak ignition coil
- Excessive spark plug gap
- Coil insulation breakdown
- Carbon tracking
- High cylinder pressure exposing a weak ignition system
Many ignition coils pass every test at idle and immediately surrender once they’re asked to do actual work.
Pattern 4: Heat-Related Failure
Some ignition coils fail only after reaching operating temperature.
Symptoms include:
- Engine starts normally
- Runs well while cold
- Misfire develops after warm-up
- P0355 returns after 15–30 minutes
Possible causes include:
- Internal winding failure
- Heat-damaged connector
- Expanding cracked insulation
- Increasing circuit resistance
Heat cycling is one of the leading causes of ignition coil failure.
Pattern 5: Fuel Injector Disabled
Some PCM strategies disable fuel delivery to protect the catalytic converter.
Scan data may show:
- Cylinder 5 injector disabled
- P0355 stored
- P0305 stored
- Severe power loss
- P0363 on some manufacturers
Disabling fuel prevents raw gasoline from damaging the catalytic converter.
Pattern 6: Freeze-Frame During Heavy Acceleration
Freeze-frame data often shows:
- Moderate to heavy throttle
- High engine load
- Elevated RPM
- Fully warmed engine
These operating conditions place maximum electrical demand on the ignition coil.
Pattern 7: Multiple Ignition Codes
P0355 may appear with:
- P0300
- P0351
- P0352
- P0353
- P0354
- P0356
Multiple ignition circuit codes often indicate:
- Shared power supply failure
- Poor engine ground
- Damaged wiring harness
- PCM connector problems
- Low charging system voltage
- PCM driver failure
When several ignition coils report problems simultaneously, inspect the shared electrical circuits before replacing individual coils.
Common Symptoms of P0355
Symptoms vary depending on whether the failure is intermittent or complete.
Common symptoms include:
- Check Engine Light
- Flashing Check Engine Light
- Rough idle
- Cylinder 5 misfire
- Engine vibration
- Hesitation
- Loss of power
- Poor acceleration
- Hard starting
- Reduced fuel economy
- Increased exhaust emissions
- Strong fuel odor
Some vehicles may continue driving relatively normally until ignition demand increases.
Check Engine Light
The Check Engine Light is typically the first symptom.
Companion codes commonly include:
- P0305
- P0300
- P0351–P0356
- P0363
A flashing Check Engine Light indicates an active catalyst-damaging misfire.
Rough Idle
A failed Ignition Coil “E” often causes:
- Engine shaking
- Uneven idle
- Increased vibration
- Rough engine operation
The idle may improve slightly as engine speed increases.
Engine Misfire
Without sufficient spark energy, Cylinder 5 cannot consistently ignite the air/fuel mixture.
Drivers may notice:
- Jerking
- Hesitation
- Bucking
- Stumbling
- Poor throttle response
- Reduced engine performance
Persistent misfires should never be ignored.
Loss of Power
When Cylinder 5 stops contributing power:
- Horsepower decreases
- Acceleration slows
- Hill climbing becomes more difficult
- Turbocharged engines often experience noticeable boost loss
The PCM may also activate a reduced-power strategy.
Poor Fuel Economy
A cylinder that misfires wastes fuel.
Drivers may experience:
- Increased fuel consumption
- Rich exhaust mixture
- Reduced combustion efficiency
- Increased emissions
Fuel economy often drops significantly until repairs are completed.
Strong Fuel Odor
A failed ignition event allows raw fuel into the exhaust.
Possible symptoms include:
- Fuel smell
- Rich exhaust odor
- Sulfur smell from an overheating catalytic converter
This should be repaired immediately to prevent catalyst damage.
Is P0355 Serious?
Yes. P0355 is considered a high-severity diagnostic trouble code.
Ignoring the problem may lead to:
- Catalytic converter damage
- Severe engine misfires
- Reduced engine performance
- Increased fuel consumption
- Higher emissions
- Engine stalling
- Additional ignition system damage
Prompt diagnosis is strongly recommended.
Can You Drive With P0355?
Limited driving may be possible, but it is not recommended.
Avoid driving if you experience:
- Flashing Check Engine Light
- Severe engine shaking
- Major loss of power
- Engine stalling
- Strong fuel odor
- Obvious active misfires
Driving with a persistent ignition failure often turns an inexpensive coil replacement into an expensive catalytic converter replacement.
P0355 vs Related Trouble Codes
Understanding related ignition system codes simplifies diagnosis.
P0355
Ignition Coil “E” Primary/Secondary Circuit Malfunction
Electrical fault affecting Ignition Coil “E.”
P0305
Cylinder 5 Misfire Detected
The PCM detects combustion failure on Cylinder 5.
P0351
Ignition Coil “A” Primary/Secondary Circuit Malfunction
Electrical fault affecting Ignition Coil “A.”
P0352
Ignition Coil “B” Primary/Secondary Circuit Malfunction
Electrical fault affecting Ignition Coil “B.”
P0353
Ignition Coil “C” Primary/Secondary Circuit Malfunction
Electrical fault affecting Ignition Coil “C.”
P0354
Ignition Coil “D” Primary/Secondary Circuit Malfunction
Electrical fault affecting Ignition Coil “D.”
P0356
Ignition Coil “F” Primary/Secondary Circuit Malfunction
Electrical fault affecting Ignition Coil “F.”
30 Common Causes of P0355
The most common causes include:
- Failed Ignition Coil “E”
- Internal coil winding failure
- Excessive spark plug gap
- Worn spark plug
- Fouled spark plug
- Oil-contaminated spark plug
- Cracked ignition coil housing
- Damaged coil boot
- Carbon tracking
- Moisture intrusion
- Open ignition coil circuit
- Shorted ignition coil circuit
- Broken wiring
- Chafed wiring harness
- Loose electrical connector
- Corroded terminals
- Oil in the spark plug well
- Coolant contamination
- Poor engine ground
- Weak battery voltage
- Charging system problems
- PCM driver circuit failure
- Incorrect spark plug
- Low-quality aftermarket ignition coil
- Engine overheating
- Rodent-damaged wiring
- Water intrusion after engine washing
- Poor previous wiring repairs
- PCM connector damage
- Failed PCM (rare)
Final Thoughts
The P0355 Ignition Coil “E” Primary/Secondary Circuit Malfunction code indicates the PCM has detected an electrical problem affecting Ignition Coil “E,” commonly associated with Cylinder 5.
Although the ignition coil itself is often responsible, the fault may also involve:
- Spark plug
- Coil boot
- Electrical connector
- Wiring harness
- Battery voltage
- Engine ground
- Oil or moisture contamination
- PCM driver circuit
Proper diagnosis should identify the exact failure before replacing components.
The next section covers:
- Complete diagnostic procedures
- Ignition coil swap testing
- Spark plug inspection
- Power and ground testing
- PCM driver diagnosis
- Wiring repairs
- Repair procedures
- Repair costs
- Manufacturer-specific troubleshooting
- Frequently asked questions
Following a structured diagnostic process helps restore proper ignition performance while preventing unnecessary parts replacement and catalytic converter damage.
Related Pro Street Diagnostic Guides
- P0300 — Random/Multiple Cylinder Misfire Detected
- P0305 — Cylinder 5 Misfire Detected
- P0351 — Ignition Coil “A” Primary/Secondary Circuit Malfunction
- P0352 — Ignition Coil “B” Primary/Secondary Circuit Malfunction
- P0353 — Ignition Coil “C” Primary/Secondary Circuit Malfunction
- P0354 — Ignition Coil “D” Primary/Secondary Circuit Malfunction
How to Diagnose the P0355 Code
Diagnosing P0355 requires determining why the Powertrain Control Module (PCM) has detected a malfunction in the Ignition Coil “E” Primary/Secondary Circuit.
Unlike P0305, which identifies a combustion misfire on Cylinder 5, P0355 is an electrical circuit code. The fault may involve the ignition coil, spark plug, wiring, connector, voltage supply, ground circuit, or PCM driver.
The most common causes include:
- Failed Ignition Coil “E”
- Worn or damaged spark plug
- Excessive spark plug gap
- Broken ignition coil wiring
- Loose or corroded connector
- Oil or moisture in the spark plug well
- Poor engine ground
- PCM ignition driver failure (rare)
Because prolonged misfires can damage the catalytic converter, diagnosis should begin as soon as possible.
Safety Precautions
Before beginning diagnosis:
- Park on level ground.
- Apply the parking brake.
- Turn the ignition off.
- Allow the engine to cool.
- Wear safety glasses.
- Wear insulated gloves when working around ignition components.
- Disconnect the battery before repairing wiring.
Modern ignition coils may produce 20,000 to 60,000 volts. Never disconnect ignition components while the engine is running.
Tools Required
Professional diagnosis may require:
- Professional scan tool
- Digital multimeter
- Automotive oscilloscope
- Adjustable spark tester
- Manufacturer wiring diagrams
- Back-probe pins
- Basic hand tools
- Battery load tester
- Dielectric grease
- Compression tester (if necessary)
A dedicated spark tester provides far more accurate results than trying to improvise with a loose spark plug.
Step 1 – Verify the Code
Connect a professional scan tool.
Record:
- Stored DTCs
- Pending DTCs
- Permanent DTCs
- Freeze-frame data
Monitor:
- Cylinder misfire counters
- Engine RPM
- Ignition timing
- Fuel trims
- Cylinder contribution
- Battery voltage
Always save freeze-frame data before clearing any codes.
Step 2 – Check for Related Trouble Codes
P0355 commonly appears with:
- P0300
- P0305
- P0351
- P0352
- P0353
- P0354
- P0356
- P0363
Related codes help determine whether the fault affects only one ignition coil or multiple cylinders.
| Code Combination | Likely Diagnosis |
|---|---|
| P0355 only | Ignition Coil “E” circuit fault |
| P0355 + P0305 | Coil, spark plug, or wiring fault on Cylinder 5 |
| P0355 + multiple P035X codes | Shared wiring, power supply, or PCM issue |
| P0355 + P0363 | Severe misfire with fuel disabled |
Step 3 – Confirm Coil Assignment
Before replacing any components, verify which cylinder corresponds to Ignition Coil “E.”
On many engines, Coil “E” controls Cylinder 5, but manufacturer assignments vary.
Confirm using:
- Factory service manual
- Wiring diagrams
- OEM connector identification
- Professional scan tool
Never assume coil lettering always matches firing order.
Step 4 – Review Freeze-Frame Data
Review:
- Engine RPM
- Engine load
- Throttle position
- Coolant temperature
- Battery voltage
- Vehicle speed
Determine whether the failure occurred:
- At idle
- During cold start
- During heavy acceleration
- Under highway cruising
- After engine warm-up
This information frequently identifies intermittent ignition failures.
Step 5 – Perform a Visual Inspection
Inspect Ignition Coil “E.”
Look for:
- Cracked housing
- Burn marks
- Carbon tracking
- Oil contamination
- Water intrusion
- Damaged coil boot
- Loose mounting bolt
Many ignition coil failures can be identified during a careful visual inspection.
Step 6 – Inspect the Wiring Harness
Trace the ignition coil wiring harness.
Inspect for:
- Broken wires
- Chafed insulation
- Melted wiring
- Heat damage
- Oil contamination
- Rodent damage
- Poor previous repairs
Repair damaged wiring before replacing ignition components.
Step 7 – Inspect the Electrical Connector
Disconnect the ignition coil connector.
Inspect for:
- Bent terminals
- Corrosion
- Loose pins
- Burned contacts
- Broken locking tabs
- Moisture intrusion
Connector failures are among the most common causes of P0355.
Step 8 – Verify Battery and Charging System Voltage
Low system voltage can interfere with ignition coil performance.
Normal readings:
- Engine off: 12.4–12.8 volts
- Engine running: 13.5–14.8 volts
Repair charging system faults before continuing diagnosis.
Step 9 – Monitor Cylinder 5 Misfire Data
Using a professional scan tool, monitor:
- Cylinder 5 misfire count
- Total misfire count
- Fuel trims
- Engine RPM
- Cylinder contribution
Rapidly increasing Cylinder 5 misfire counts usually indicate an ignition system problem.
Step 10 – Perform an Ignition Coil Swap Test
Move Ignition Coil “E” to another cylinder.
For example:
- Move Coil “E” from Cylinder 5 to Cylinder 3.
- Clear all codes.
- Road test the vehicle.
- Rescan for DTCs.
If the fault moves:
- P0305 → P0303
- Or the ignition coil fault follows the coil
the ignition coil is defective.
If P0355 remains assigned to the original circuit, suspect wiring, connector, power supply, or PCM control issues.
Step 11 – Inspect the Spark Plug
Remove the Cylinder 5 spark plug.
Inspect for:
- Excessive gap
- Carbon fouling
- Oil fouling
- Burned electrodes
- Cracked porcelain
- Incorrect heat range
A worn spark plug places additional stress on the ignition coil and may contribute to repeat failures.
Step 12 – Test Spark Output
Use an adjustable spark tester.
Verify:
- Strong spark
- Consistent spark
- Proper spark duration
- No intermittent dropout
Weak spark supports an ignition coil, wiring, voltage supply, or PCM control problem.
Step 13 – Verify Coil Power Supply
Using a multimeter:
Verify:
- Battery voltage at the ignition coil connector
- Stable voltage during cranking
- Minimal voltage drop
If voltage is missing, inspect:
- Ignition fuse
- Main relay
- Shared ignition power circuit
- Wiring harness
Multiple ignition coil codes often indicate a shared power supply problem.
Step 14 – Verify Ground Integrity
Inspect:
- Battery grounds
- Engine grounds
- Cylinder head grounds
- PCM grounds
Verify:
- Proper continuity
- Low resistance
- Minimal voltage drop
Poor grounds can create intermittent ignition coil circuit faults.
Step 15 – Test the PCM Control Signal
Using an oscilloscope or logic probe:
Verify:
- Proper switching pulse
- Stable waveform
- No intermittent signal loss
- No short to power or ground
A missing PCM control signal may indicate:
- Broken control wire
- Shorted circuit
- Connector failure
- PCM driver failure
PCM failure should only be considered after every other component has passed inspection.
Step 16 – Test Ignition Coil Resistance
Where applicable, compare:
- Primary winding resistance
- Secondary winding resistance
to manufacturer specifications.
Many modern smart coils contain internal electronics, making waveform analysis and swap testing more accurate than resistance testing alone.
Step 17 – Inspect for Oil or Coolant Contamination
Inspect the spark plug well for:
- Engine oil
- Coolant
- Water
- Dirt
- Carbon tracking
Common sources include:
- Valve cover gasket leaks
- Spark plug tube seal leaks
- Coolant leaks
- Engine washing
Repair all leaks before installing replacement ignition components.
Step 18 – Check Cylinder Compression (If Necessary)
If all ignition system tests pass but Cylinder 5 continues to misfire:
Perform:
- Compression test
- Leak-down test
- Injector balance test
Possible mechanical faults include:
- Burned exhaust valve
- Low compression
- Worn piston rings
- Head gasket failure
- Fuel injector malfunction
Mechanical failures usually trigger P0305, but multiple faults may exist simultaneously.
Step 19 – Review Technical Service Bulletins
Check manufacturer Technical Service Bulletins (TSBs) for:
- Ignition coil failures
- Wiring harness updates
- PCM software revisions
- Connector improvements
- Misfire calibration updates
- Water intrusion issues
Factory bulletins often identify known vehicle-specific failures.
Step 20 – Confirm the Diagnosis
Before replacing expensive components, verify:
- Correct Ignition Coil “E” assignment
- Ignition coil condition
- Spark plug condition
- Coil boot integrity
- Wiring continuity
- Connector condition
- Battery voltage
- Engine grounds
- PCM control signal
- Cylinder compression (if necessary)
Completing these diagnostic procedures accurately identifies the root cause of P0355 while preventing unnecessary parts replacement.
Step 21 – Replace the Ignition Coil
If testing confirms Ignition Coil “E” has failed, replacement is the proper repair.
Common signs of ignition coil failure include:
- P0355 immediately returns after clearing
- Cylinder 5 misfire
- Rough idle
- Engine hesitation
- Hard starting
- Loss of power
- Flashing Check Engine Light
General replacement procedure:
- Disconnect the negative battery cable.
- Remove any engine covers.
- Disconnect the ignition coil electrical connector.
- Remove the ignition coil retaining bolt.
- Carefully pull the ignition coil straight upward.
- Inspect the spark plug well for oil, coolant, or moisture.
- Install a new OEM-quality ignition coil.
- Apply dielectric grease to the coil boot if recommended.
- Reconnect the electrical connector.
- Clear all diagnostic trouble codes.
Using OEM or premium aftermarket ignition coils provides the best reliability and helps prevent repeat failures.
Step 22 – Replace the Spark Plug
A worn spark plug often contributes to ignition coil failure.
Inspect the spark plug for:
- Excessive electrode gap
- Carbon fouling
- Oil contamination
- Burned electrodes
- Cracked porcelain
- Incorrect heat range
- Damaged threads
Replace spark plugs according to manufacturer specifications.
If the spark plug has excessive wear, replacing only the ignition coil may result in another failure shortly afterward.
Step 23 – Repair Wiring Problems
Inspect the complete ignition coil wiring harness.
Look for:
- Broken wires
- Chafed insulation
- Melted insulation
- Heat damage
- Oil contamination
- Rodent damage
- Poor previous repairs
Repair damaged wiring using:
- Soldered wire repairs
- Heat-shrink tubing
- OEM repair connectors
- Proper wire routing
Many intermittent P0355 faults are caused by damaged wiring rather than the ignition coil itself.
Step 24 – Repair or Replace Electrical Connectors
Inspect the ignition coil connector for:
- Bent terminals
- Loose pins
- Corroded contacts
- Burned terminals
- Moisture intrusion
- Broken locking tabs
Replace damaged connectors using OEM repair kits whenever possible.
A loose connector can produce the same symptoms as a failed ignition coil.
Step 25 – Repair Oil or Coolant Leaks
Contamination inside the spark plug well dramatically shortens ignition coil life.
Inspect for:
- Valve cover gasket leaks
- Spark plug tube seal leaks
- Coolant leaks
- Water intrusion
Repair all leaks before installing replacement ignition components.
Ignoring the leak almost guarantees another ignition coil failure.
Step 26 – Repair Engine Ground Problems
Inspect all ignition-related grounds.
Verify:
- Battery grounds
- Engine block grounds
- Cylinder head grounds
- PCM grounds
- Chassis grounds
Poor grounding can create:
- Weak spark
- Intermittent misfires
- Ignition coil circuit faults
- False diagnostic trouble codes
Clean and tighten all ground connections before condemning expensive components.
Step 27 – Repair the PCM Driver Circuit (If Necessary)
If testing confirms the ignition coil, spark plug, wiring, connectors, voltage supply, and grounds are functioning correctly:
Inspect:
- PCM ignition driver output
- Control wire continuity
- Oscilloscope waveform
- PCM connector terminals
PCM driver failures are uncommon and should only be considered after eliminating every other possible cause.
Step 28 – Update PCM Software
Before replacing the PCM:
Review manufacturer Technical Service Bulletins (TSBs).
Manufacturers occasionally release software updates correcting:
- False ignition coil circuit detection
- Misfire detection calibration
- Ignition timing revisions
- PCM software bugs
Always install the latest PCM calibration when applicable.
Step 29 – Complete an OBD-II Drive Cycle
After repairs:
- Clear all diagnostic trouble codes.
- Start the engine.
- Allow it to reach operating temperature.
- Complete the manufacturer’s recommended drive cycle.
- Verify readiness monitors complete successfully.
Confirm that P0355 does not return.
Step 30 – Verify the Repair
After repairs:
- Clear all diagnostic trouble codes.
- Start the engine.
- Verify a smooth idle.
- Road test the vehicle.
- Monitor Cylinder 5 misfire counters.
- Verify stable ignition timing.
- Confirm no pending or permanent DTCs return.
- Ensure the Check Engine Light remains off.
A successful repair restores full engine performance, smooth operation, proper fuel economy, and reliable ignition system function.
How to Fix P0355
The proper repair depends entirely on the diagnostic results.
Common repairs include:
- Replacing Ignition Coil “E”
- Replacing worn spark plugs
- Repairing damaged wiring
- Replacing faulty electrical connectors
- Repairing valve cover gasket leaks
- Repairing spark plug tube seals
- Repairing engine ground connections
- Updating PCM software
- Replacing the PCM (rare)
Never replace the PCM until every ignition component and electrical circuit has been thoroughly tested.
Typical Repair Costs
| Repair | Typical Cost |
|---|---|
| Professional diagnosis | $100–250 |
| Ignition coil replacement | $125–350 |
| Spark plug replacement | $150–450 |
| Ignition coil connector replacement | $100–250 |
| Wiring repair | $100–350 |
| Valve cover gasket replacement | $200–600 |
| Spark plug tube seal replacement | $250–700 |
| Engine ground repair | $75–200 |
| PCM software update | $100–250 |
| PCM replacement (rare) | $800–2,000+ |
Repair costs vary depending on labor rates, engine configuration, and component accessibility.
Common Diagnostic Mistakes
Avoid these common mistakes:
- Replacing the ignition coil without inspecting the spark plug
- Ignoring oil contamination inside the spark plug well
- Skipping wiring continuity testing
- Overlooking loose electrical connectors
- Ignoring charging system voltage
- Clearing codes before recording freeze-frame data
- Replacing the PCM without verifying the control circuit
- Installing low-quality aftermarket ignition coils
Many P0355 repairs involve spark plugs, wiring, or connector problems—not PCM failure.
Manufacturer-Specific Notes
General Motors (Chevrolet, GMC, Cadillac, Buick)
Inspect:
- Coil-on-plug ignition coils
- Valve cover oil leaks
- Coil connectors
- Engine grounds
Heat exposure is a common cause of ignition coil failure on high-mileage GM engines.
Ford/Lincoln
Inspect:
- COP ignition coils
- Spark plug condition
- Coil boots
- Moisture intrusion
Many Ford engines experience intermittent ignition failures that become noticeable under heavy acceleration.
Chrysler, Dodge, Jeep, Ram
Inspect:
- Ignition coil connectors
- PCM driver circuits
- Wiring near exhaust manifolds
- Spark plug wells
Heat-related wiring damage is a common failure point.
Toyota/Lexus
Inspect:
- Denso ignition coils
- Spark plug tube seals
- Coil connectors
- Valve cover gasket leaks
Oil contamination frequently causes repeat ignition coil failures.
Nissan/Infiniti
Inspect:
- Ignition coil boots
- Spark plug wells
- Wiring harness
- Engine grounds
Several Nissan V6 engines develop ignition coil failures after repeated heat cycling.
Honda/Acura
Inspect:
- Coil-on-plug assemblies
- Valve adjustment history
- Spark plugs
- Oil contamination
OEM ignition components generally provide the most reliable long-term repair.
Frequently Asked Questions
What usually fixes P0355?
The most common repairs include replacing a failed ignition coil, replacing worn spark plugs, repairing damaged wiring, replacing faulty electrical connectors, repairing oil leaks into the spark plug wells, or correcting poor engine ground connections.
Can I drive with P0355?
Limited driving may be possible, but repairs should be completed immediately. Driving with an active ignition fault can lead to catalytic converter damage, poor engine performance, increased fuel consumption, and additional ignition system failures.
Does P0355 always mean the ignition coil is bad?
No. While the ignition coil is the most common cause, P0355 may also result from damaged wiring, faulty connectors, worn spark plugs, oil contamination, poor ground connections, or a failed PCM driver circuit.
Can a bad spark plug cause P0355?
Yes. A worn or improperly gapped spark plug increases ignition voltage demand, placing additional stress on the ignition coil and potentially triggering P0355.
Is P0355 a serious code?
Yes. P0355 is considered a high-severity diagnostic trouble code. Ignoring it can result in severe engine misfires, catalytic converter damage, reduced fuel economy, increased emissions, and poor engine performance.
Final Thoughts
The P0355 Ignition Coil “E” Primary/Secondary Circuit Malfunction code indicates the PCM has detected an electrical fault affecting the ignition system. While a failed ignition coil is the most common cause, the root problem may also involve worn spark plugs, damaged wiring, poor electrical connections, oil contamination, valve cover leaks, or PCM driver issues.
Fortunately, ignition coil failures, spark plug wear, damaged connectors, wiring faults, and oil contamination account for the overwhelming majority of P0355 repairs.
A complete diagnosis should always verify:
- Ignition coil condition
- Spark plug condition
- Coil connector integrity
- Wiring harness condition
- Battery voltage
- Engine ground quality
- PCM control signal
- PCM software version
Following a structured diagnostic process prevents unnecessary parts replacement while restoring reliable ignition performance, smooth engine operation, maximum fuel economy, and long-term engine reliability.
Continue Your Pro Street Ignition System Series
Related guides include:
- P0300 – Random/Multiple Cylinder Misfire Detected
- P0305 – Cylinder 5 Misfire Detected
- P0351 – Ignition Coil “A” Primary/Secondary Circuit Malfunction
- P0352 – Ignition Coil “B” Primary/Secondary Circuit Malfunction
- P0353 – Ignition Coil “C” Primary/Secondary Circuit Malfunction
- P0354 – Ignition Coil “D” Primary/Secondary Circuit Malfunction
