OBD-II Code P0358: Ignition Coil 'H' (Cylinder 8) Circuit Malfunction

What Does P0358 Mean?

Code P0358 means the Powertrain Control Module (PCM) detects an electrical problem with the ignition coil for cylinder 8. This coil creates the high-voltage spark needed to ignite fuel. The code indicates an open or short in the coil's primary (low voltage) or secondary (high voltage) circuit, preventing proper spark generation.

Technical definition: SAE/OBD-II definition: "Ignition Coil 'H' Primary/Secondary Circuit Malfunction." The PCM cannot control the cylinder 8 ignition coil due to an electrical circuit fault. The PCM's internal driver circuit detects an open, a short to ground, or a short to voltage.

Can I Drive With P0358?

yes_but_critically_limited. You can drive short distances, but it is highly discouraged. Cylinder 8 is not firing, causing reduced power, rough running, and poor fuel economy. A FLASHING check engine light signifies a severe misfire dumping unburned fuel into the exhaust. Stop driving immediately to prevent catastrophic catalytic converter damage costing $1,000 to $4,000.

Common Causes

• Defective Ignition Coil on Cylinder 8 (Very Common) — This accounts for over 90% of cases. The internal copper windings of the ignition coil break or short out from constant heat cycles and age, preventing spark generation.
• Damaged Wiring or Connector (Common) — The wiring harness or plastic connector becomes frayed, corroded, or chewed by rodents. Broken locking tabs cause loose connections, while internal wire breaks create intermittent shorts.
• Worn or Fouled Spark Plug (Less Common) — A bad spark plug in cylinder 8 with an excessive gap or heavy fouling forces the ignition coil to generate higher voltage. This overheats the coil and causes premature failure.
• Leaking Valve Cover Gasket (Less Common) — Oil leaking into the spark plug tube saturates the ignition coil boot and the coil itself, causing it to short out. This guarantees repeat coil failures if the oil leak is ignored.
• Faulty Powertrain Control Module (PCM) (Very Rare) — The internal driver circuit inside the PCM that controls the cylinder 8 ignition coil fails. Consider this only after exhaustively testing all wiring, grounds, and connections.

Symptoms

• Check Engine Light is On or Flashing — A solid light is standard. A flashing light signals a severe, catalyst-damaging misfire requiring immediate engine shutdown.
• Rough Idle and Engine Shaking — The engine shakes or vibrates noticeably, especially when stopped at a light, because cylinder 8 is dead.
• Reduced Engine Power and Hesitation — The vehicle feels sluggish, weak, and hesitates during acceleration because it is running on seven cylinders.
• Fuel Smell from Exhaust — Raw gasoline smell emits from the exhaust pipe as the non-firing cylinder dumps unburned fuel directly into the exhaust system.
• Increased Fuel Consumption — Unburned fuel is wasted, and the engine's overall efficiency drops, leading to a 10-25% decrease in gas mileage.
• Difficulty Starting the Engine — The engine takes longer to crank or struggles to start in cold weather due to the loss of one cylinder's compression.
• Failed Emissions Test (also visible on scanner) — An active P0358 code and misfire automatically fails state emissions or smog inspections.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this code.

Common Fixes & Costs

• Replace Ignition Coil 'H' (Cylinder 8) — Parts: $40-$100, Labor: $75-$150, ~0.8 hr book time (DIY)
• Replace Spark Plug and Ignition Coil on Cylinder 8 — Parts: $50-$130, Labor: $100-$200, ~1.1 hr book time (DIY)
• Repair Wiring Harness or Connector — Parts: $15-$75, Labor: $100-$300, ~1.5 hr book time (Intermediate)
• Replace All 8 Ignition Coils and Spark Plugs — Parts: $350-$800, Labor: $200-$400, ~2.5 hr book time (Intermediate)
• Replace Powertrain Control Module (PCM) — Parts: $800-$1,500, Labor: $150-$250, ~1.5 hr book time (Professional)

Used vs. New Parts: Buying Guide

When a used part is worth it: For an inexpensive, high-mileage vehicle where the goal is simply to get it running, a used OEM ignition coil from a salvage yard is a budget-friendly option. It is not recommended for long-term reliability.

Donor-vehicle mileage cap: roughly under 60000 miles for the part to have meaningful remaining life.

Donor quality checklist:

• Verify the part number exactly matches your original coil.
• Inspect the used coil for cracks, corrosion, or signs of oil saturation.
• Ask for a short-term warranty (e.g., 30-90 days).

Decision logic:

• If The vehicle has low to moderate mileage (<100K miles) and you plan to keep it. → Buy a new OEM or high-quality aftermarket coil. The cost difference is minimal compared to the risk of a repeat failure.
• If The vehicle is very old (>150K miles) and you have a tight budget. → A tested, used OEM coil is an acceptable risk, but it has limited remaining life.
• If You are replacing coils that are difficult to access (requiring intake manifold removal). → Always buy new. The labor cost is too high to risk using a part with an unknown history.

Warranty tradeoff: Used parts offer a 30-90 day warranty. Quality aftermarket new coils come with a 1-year to limited lifetime warranty. New OEM parts usually have a 12-month warranty.

Worst-case if a used part fails: $150-$300 if a used coil fails shortly after installation, primarily due to repeated labor costs.

What Happens If You Wait — Timeline

1. 0-1 week: Code P0358 sets, solid Check Engine Light appears. Misfire causes a slight rough idle or hesitation. Some PCMs disable the cylinder 8 fuel injector. (MPG impact: 5-10%% · Added cost: $0)
2. 1 week - 2 months: Engine shake at idle becomes pronounced. Noticeable loss of power. The Check Engine Light flashes during heavy load, indicating raw fuel is entering the exhaust. (MPG impact: 10-20%% · Added cost: $50-100 in wasted fuel.)
3. 2-4 months: The catalytic converter overheats and its internal ceramic substrate melts from unburned fuel saturation. Rotten egg smells emit from the exhaust. (MPG impact: 15-25%% · Added cost: $1,200-$2,500 (catalytic converter replacement required).)
4. 4+ months: Complete catalytic converter meltdown. The exhaust physically blocks, causing extreme power loss (max 20 mph) and backpressure damage to engine gaskets and oxygen sensors. (MPG impact: 25-50%+% · Added cost: $1,500-$4,000+ (catalytic converter, oxygen sensors, and engine repairs).)

Cost of Not Fixing It

• Immediate (0-1 month): Significant drop in fuel economy (10-25%), rough engine operation, poor acceleration, and failed emissions test. (Added cost: $50-$150 per month in wasted fuel.)
• Short-Term (1-6 months): Catastrophic failure of the catalytic converter due to overheating from raw fuel dumped into the exhaust. This is the primary financial risk. (Added cost: $1,200-$3,500 for catalytic converter replacement.)
• Long-Term (6+ months): Damage to oxygen sensors and internal engine parts due to excessive vibration and improper combustion. (Added cost: $200-$800+ for oxygen sensors or related repairs.)

Diagnosis Steps

1. Read the Trouble Codes
   Use an OBD-II scanner to confirm P0358. Note companion codes like P0308 (Cylinder 8 Misfire). Freeze frame data shows engine conditions when the fault occurred.
   Tools: OBD-II Scanner (Beginner)
2. Locate Cylinder 8
   Find cylinder #8 using a repair manual. Coil 'H' corresponds to cylinder 8. Layouts vary (e.g., rear passenger side on Ford V8s, rear driver's side on GM V8s).
   Tools: Repair manual or internet access (Beginner)
3. Perform the 'Swap Test'
   Swap the cylinder 8 ignition coil with an adjacent cylinder (like 6 or 7). Clear codes and start the engine. If the code changes to the new cylinder (e.g., P0357), the coil is bad. If P0358 returns, the circuit is faulty.
   Tools: Socket/ratchet set, OBD-II scanner (Beginner)
4. Inspect the Wiring and Connector
   Check the cylinder 8 coil connector for broken locking tabs, corroded pins, or melted plastic. Wiggle the harness while the engine runs to test for intermittent misfires.
   Tools: Flashlight, inspection mirror (Intermediate)
5. Check the Spark Plug
   Remove the cylinder 8 spark plug. Inspect for excessive gap, oil fouling, or cracked porcelain. A bad plug forces the coil to work harder, causing premature failure.
   Tools: Spark plug socket, ratchet (Intermediate)
6. Test the Coil Power Supply
   With Key On, Engine Off, use a multimeter to check the power feed wire at the coil connector. It should read ~12 volts. No voltage indicates an open circuit from the fuse or relay.
   Tools: Multimeter (Advanced)
7. PRO TIP: Test the PCM Driver Signal
   The PCM fires the coil by pulsing a ground signal. Connect a multimeter (DC volts) between the control wire pin and battery positive. Crank the engine; voltage should fluctuate. A steady 12V means the PCM is not providing the ground pulse.
   Tools: Multimeter or Noid Light (Advanced)
8. PRO TIP: Test Coil Resistance
   Measure primary resistance (0.4-2.0 Ohms) between the coil's positive and negative terminals. Measure secondary resistance (6,000-15,000 Ohms) between the positive terminal and the high-voltage boot. Infinity (OL) means an open circuit; near zero means a short.
   Tools: Multimeter, Service Manual (Advanced)
9. PRO TIP: Analyze with an Oscilloscope
   View the primary waveform. A healthy coil shows a sharp voltage spike followed by a ringing pattern. A flat line confirms the PCM command is missing or the coil is internally open.
   Tools: Automotive Oscilloscope (Professional)

When This Code Triggers (Freeze-Frame Conditions)

• Engine Coolant Temp: 180-200°F (Fully warmed up, after several minutes of driving.)
• Engine RPM: 1500-3000 RPM (Under moderate load, such as steady acceleration or cruising.)
• Engine Load: 30-60% (The fault is most apparent when the engine is working, not just idling.)
• Vehicle Speed: 35-60 mph (Often occurs during city or highway driving, not just at a standstill.)

Related Codes

• P0308 — Means 'Cylinder 8 Misfire Detected.' It almost always appears with P0358. P0358 is the electrical cause (circuit fault), while P0308 is the mechanical effect (crankshaft slowed down).
• P0300 — Means 'Random/Multiple Cylinder Misfire Detected.' Appears with P0358 if engine vibration from the dead cylinder confuses the crankshaft position sensor, or if a bad ground intermittently affects other coils.
• P0351-P0357 — These are identical circuit malfunction codes for cylinders 1 through 7. Seeing multiple codes (e.g., P0358 and P0352) strongly points to a shared problem, like a damaged wiring harness or failing PCM.
• P0363 — Means 'Misfire Detected – Fueling Disabled.' The PCM intentionally shuts off the fuel injector to the misfiring cylinder to protect the catalytic converter from raw fuel saturation.

Climate & Environmental Factors

• Extreme Heat: High temperatures in the engine bay accelerate the breakdown of the coil's internal epoxy and copper windings, leading to shorts or open circuits.
• High Humidity: Moisture causes condensation on electrical connectors. This promotes corrosion on pins and causes high voltage to arc to ground instead of firing the plug, triggering a circuit fault.
• Cold Weather: Cold temperatures increase electrical resistance. A weak coil fails to produce a strong enough spark to start a cold engine, making its weakness apparent.

How to Talk to a Mechanic About This Code

Say this: "I have a P0358 code for the cylinder 8 ignition coil circuit and a noticeable misfire. I'd like to schedule a diagnostic. Please start by swapping the coil with an adjacent cylinder to see if the fault follows the coil before recommending parts."

This signals you understand the most efficient first diagnostic step. It directs the mechanic toward a logical, no-cost test (the 'swap test') and prevents them from immediately selling you a new coil that might not be necessary.

Avoid saying:

• 'My check engine light is on, can you look at it?' (Too vague, invites an expensive diagnostic process).
• 'Just fix the misfire.' (Leads to unnecessary parts being replaced without proper diagnosis).
• 'My car is shaking, I think it needs a tune-up.' (Suggests a solution without stating the specific code, leading to unneeded services).

Questions to ask before authorizing the repair:

• Did the fault code move to the other cylinder after you swapped the ignition coil?
• If the code did not move, what were the voltage and ground signal readings at the coil connector?
• Can you show me the damaged wiring or corroded connector pin if that's the issue?
• What is the warranty on the replacement part and your labor?

Where to Take It: Dealer vs Independent vs Chain

• Dealer: Use only for warranty claims or as a last resort if an independent shop suspects a bad PCM requiring programming.
  Best for: Vehicles still under powertrain or emissions warranty., Complex electrical issues where a PCM replacement and manufacturer-specific programming is required., Known manufacturer-specific quirks documented in TSBs only available to dealers.
  Downsides: Highest labor rates, often 1.5-2x more than independent shops., May default to replacing an entire wiring harness instead of repairing a single wire. (Typical cost: +50% vs. baseline)
• Independent Shop: Best fit. A reputable independent shop easily handles the 'swap test', electrical testing, and coil replacement for a reasonable price.
  Best for: Out-of-warranty vehicles where cost is a factor., Diagnosing common codes like P0358 with well-understood causes (bad coil, wiring, or spark plug)., Building a long-term relationship with a trusted mechanic.
  Downsides: Quality varies greatly; vetting the shop through reviews and ASE certifications is crucial., May lack proprietary tools for PCM programming on newer vehicles. (Typical cost: +0% vs. baseline)
• Chain Shop: Use with caution. Acceptable for reading codes for free, but avoid for actual diagnosis.
  Best for: Simple parts replacement IF you already diagnosed the problem (e.g., 'Please replace the ignition coil on cylinder 8')., Reading the code for free.
  Downsides: Technician skill varies dramatically; they may lack training in electrical diagnostics., High pressure to sell parts leads to unnecessary replacements., Often lack advanced diagnostic tools for wiring faults. (Typical cost: -10% vs. baseline)

When to Walk Away From the Repair

If the estimated repair cost exceeds 50% of the car's private-party value, seriously consider selling or trading it in.

• Car worth $12000, fix is $250: Fix it. This is a routine repair and well below the threshold.
• Car worth $4000, fix is $300: Fix it. The repair cost is a small fraction of the car's value.
• Car worth $2500, fix is $1750: Walk away. A rare PCM failure costing 70% of the car's value is not economically sound.

What Scan Tool You Need for This Code

Minimum: A basic OBD-II code reader that reads/clears codes and displays freeze frame data.

A $20 reader confirms P0358, but you need a tool that reliably clears the code after the 'swap test' to see if the fault moves. Viewing freeze frame data is crucial to see engine conditions when the fault occurred.

Budget: BlueDriver Pro (~$100) — Connects to your smartphone via Bluetooth. It reads/clears codes, shows freeze frame data, and graphs live data, which is perfect for confirming swap test results.

Mid-range: Foxwell NT510 Elite (~$180) — A handheld unit providing manufacturer-specific codes and bidirectional control. It performs active tests, like commanding coils, helping pinpoint a wiring or PCM driver issue without a multimeter.

Professional: Autel MaxiCOM MK808S (~$450) — Offers full bidirectional control to activate individual coils and confirm circuit integrity. Displays extensive live data streams, including misfire counts per cylinder. Overkill for one code, but invaluable for serious DIYers.

Rent vs buy: Auto parts stores read codes for free, which gets you the P0358 code. However, they won't clear codes for you. To properly perform the 'swap test', you must buy your own scanner. A budget pick is a worthwhile investment.

How to Clear the Code After You Fix It

1. Reconnect the battery if it was disconnected.
2. Use an OBD-II scan tool to erase the P0358 trouble code from the PCM's memory.
3. Perform a complete OBD-II drive cycle to allow the vehicle's onboard diagnostics to run and confirm the repair.

Drive cycle (~30 minutes): A generic drive cycle includes a cold start (engine sits for 8+ hours), 2-3 minutes of idling, 10-15 minutes of mixed city/highway driving (reaching speeds of 55-60 mph), and a cool-down period. This allows readiness monitors to run.

Readiness monitors affected: Catalyst Monitor, Misfire Monitor, Oxygen (O2) Sensor Monitor, Evaporative System (EVAP) Monitor

Before emissions retest: drive at least 100 miles to fully set monitors.

Watch out for:

• Disconnecting the battery clears the Check Engine Light but resets all readiness monitors to 'Not Ready', causing an automatic emissions test failure.
• The P0358 code returns immediately if the underlying electrical fault (bad coil, wiring) was not fixed.

Will This Fail Emissions / State Inspection?

Yes — this code typically fails an OBD-II emissions inspection.

• California: An active P0358 code is an automatic failure for a smog check. After repairs, a full drive cycle must be completed to set all readiness monitors to 'Ready' before a re-test.
• New York: The NYS DMV inspection includes an OBD-II scan. The presence of a P0358 fault code results in an immediate emissions test failure.
• Texas: In the 17 counties requiring emissions testing, a vehicle with an illuminated Check Engine Light and an active P0358 code fails the OBD portion of the state inspection.

Most Commonly Affected Vehicles

• Ford F-150 (2004-2010) — The 5.4L 3V Triton engine is notorious for this code. Plastic locking tabs on coil connectors become brittle and break, causing loose connections. Valve cover oil leaks also destroy coils.
• Dodge Ram 1500 (2009-2018) — The 5.7L HEMI V8 commonly experiences this code. Coils for rear cylinders (7 and 8) fail from high heat exposure. Replace the spark plug simultaneously.
• Chevrolet Silverado 1500 (2007-2013) — The 5.3L and 6.0L V8 engines are susceptible. The coil control wire between the coil and the ECM frequently develops an open or short.
• GMC Sierra (2007-2013) — Mechanically identical to the Silverado, these trucks share the same V8 engines and experience identical ignition coil failure patterns on rear cylinders.
• Cadillac Escalade (2007-2014) — The 6.2L V8 engine is prone to this code due to original equipment ignition coils reaching the end of their service life after 100,000-120,000 miles.
• Toyota Tundra (2007-2021) — The 4.7L and 5.7L V8s set this code. On some 4.7L engines, coils 2, 3, 5, and 8 share an ignition feedback (IGF2) signal wire. A fault in this wire causes all four cylinders to log circuit faults simultaneously.
• Nissan Titan (2004-2022) — The 5.6L V8 engine sets this code due to straightforward ignition coil failure from age and heat.
• BMW X5 (2008-2018) — V8 models with the N62 or N63 engine log P0358. Diagnosis is complex due to tight packaging. Oil leaks from valve cover gaskets are a frequent underlying cause.

Manufacturer-Specific Notes

• Ford: On many V8 engines, the PCM intentionally shuts down the fuel injector to cylinder 8 when it detects P0358, setting a P0363 code. This protects the catalytic converter but makes the misfire feel more violent.
• Chrysler/Dodge/Jeep: On 5.7L HEMI engines, ignition coils fail due to heat exposure, especially on rear cylinders. Apply dielectric grease to the new coil boot to insulate against moisture and heat.
• Toyota: On some V8 engines, coils 2, 3, 5, and 8 share an ignition feedback (IGF2) signal wire. A short in this single shared wire causes all four cylinders to log circuit faults simultaneously.
• General Motors (Chevrolet/GMC): For GM V8s, P0358 sets when the PCM detects the ignition control circuit is grounded, open, or shorted to voltage for less than 1 second. The control wire from the ECM to the coil is a frequent culprit.

Real Owner Stories

2004 Ford F-150 5.4L at 202K miles

Check engine light came on with code P0358. Engine misfired only at idle.

What they tried:

1. Replaced all spark plugs.
2. Replaced ignition coil on cylinder #8.
3. Swapped the new coil pack to another cylinder, but the P0358 code remained on cylinder #8.

Outcome: The problem was not the coil or plug. The owner found a broken locking tab on the wiring connector causing a loose connection.

Lesson: If the 'swap test' fails and the code does not move to the new cylinder, the problem is in the wiring or the PCM. Stop replacing coils.

2007 Ford F-150 5.4L at 118K miles

Vehicle shuddered with multiple ignition coil codes (P0351, P0354, P0355, P0358). The A/C stopped working simultaneously.

What they tried:

1. Replaced all spark plugs.
2. Replaced COPs on cylinders 1, 4, 5, and 8.
3. Swapped the fuel injector on cylinder #8.

Outcome: A coil wire rubbed against an A/C line, causing a short that triggered the coil codes and disabled the A/C circuit.

Lesson: When multiple coil codes appear alongside unrelated electrical failures, suspect a systemic wiring short or a bad PCM ground.

2005 Chevy Silverado 5.3L with P0358 after plug change

P0358 code appeared immediately after changing the spark plugs.

What they tried:

1. Owner suspected a defective new spark plug.

Outcome: The owner accidentally pulled the wiring harness too hard during the plug change, unseating a pin inside the coil connector.

Lesson: If a code appears immediately after a repair, re-check your work. A connector was likely not seated properly or a wire was disturbed.

How to Prevent This Code From Triggering

• Replace Spark Plugs at Recommended Intervals (Every 60,000-100,000 miles, per vehicle manufacturer) — Worn spark plugs with a large gap force the ignition coil to produce a much higher voltage, putting extra strain on internal windings and causing premature failure.
• Address Engine Oil Leaks Promptly (As needed) — Oil leaking from a valve cover gasket seeps into spark plug tubes, saturating the ignition coil boot and causing the coil to short out.
• Use Dielectric Grease on Coil Boots (When replacing coils or spark plugs) — Applying dielectric grease to the inside of the coil boot and connector seal prevents moisture intrusion, stopping corrosion and high-voltage arcing.
• Perform Regular Engine Bay Inspections (Every oil change) — Inspect coil connectors for broken locking tabs and wiring harnesses for rubbing against hot components to catch circuit faults before they trigger codes.

Frequently Asked Questions

What does the 'H' in P0358 mean?

The 'H' refers to the eighth cylinder in the engine's firing sequence (A=1, B=2... H=8). This code specifically points to an electrical problem with the ignition system for cylinder number 8.

What is the most common misdiagnosis for P0358?

The most common mistake is immediately replacing the ignition coil without performing the 'swap test' or inspecting the wiring. The code indicates a circuit problem, which is often just a broken connector tab or frayed wire. Swapping the coil with a neighboring one confirms if the coil itself is the problem for free.

Is it safe to drive with a P0358 code?

Driving is highly discouraged. If the Check Engine Light is flashing, you must pull over and stop driving immediately. A flashing light indicates a severe misfire that destroys your catalytic converter in minutes, costing over $1,500 to repair.

Why did my car get a P0358 code if I already replaced the coil?

If you replaced the coil and P0358 returns, the fault lies in the wiring or PCM. Carefully re-inspect the connector for loose pins and check the wiring harness for damage. Next, test the power and signal wires using a multimeter.

What's the difference between P0358 and P0308?

P0358 is an electrical circuit code indicating the PCM detects an open or short in the cylinder 8 wiring or coil. P0308 is a performance code indicating the crankshaft slowed down when cylinder 8 was supposed to fire. P0358 is the specific electrical cause, and P0308 is the resulting mechanical effect.

Should I replace all 8 ignition coils at once?

You only need to replace the failed coil. However, since all coils are the same age, others often fail in the following months. If your budget allows and the coils require removing the intake manifold, replacing them all saves future labor costs.

Can a bad battery cause a P0358 code?

A weak battery causes numerous electrical problems, but it rarely triggers a fault code for a single ignition coil. Low voltage typically triggers multiple, unrelated codes across different systems, not an isolated P0358.

Key Takeaways

• Code P0358 indicates a specific electrical circuit failure in the cylinder 8 ignition coil, not a general mechanical misfire.
• Perform a free 'swap test' by moving the cylinder 8 coil to cylinder 7 to confirm if the coil is dead before spending $40-$100 on replacement parts.
• A flashing Check Engine Light means raw fuel is entering the exhaust; stop driving immediately to prevent $1,500+ in catastrophic catalytic converter damage.
• If replacing the coil does not clear the code, inspect the plastic connector for broken locking tabs or test the wiring harness for 12V power.