P0358 — Ignition Coil “H” Primary/Secondary Circuit #

The description of this diagnostic trouble code (DTC) may vary depending on the vehicle manufacturer. Always refer to your vehicle’s OEM (Original Equipment Manufacturer) service documentation for the most accurate wording.

Known description variations:

• Toyota: Ignition Coil “H” Primary/Secondary Circuit Malfunction
• Ford: Ignition Coil H Circuit Malfunction
• GM: Cylinder 8 Ignition Coil Circuit
• Chrysler: Ignition Coil #8 Circuit

Code P0358 Overview #

P0358 signals a detected issue in the electrical circuit of the ignition coil labeled “H”—often corresponding to cylinder 8 in V8 engine configurations. Your vehicle’s Engine Control Module (ECM) or Powertrain Control Module (PCM) constantly monitors both the primary (low voltage) and secondary (high voltage) sides of the ignition coil circuits. If the ECM detects an abnormality—such as an open, short, or unexpected voltage—it triggers this code. This malfunction can manifest as engine misfires, rough running, or difficulty starting. In some cases, you may not notice any immediate symptoms, but ignoring this code can lead to more serious engine issues over time.

Frequent Symptoms for DTC P0358 #

When P0358 is present, your vehicle may show clear or subtle signs. The most common symptom is a noticeable engine misfire, especially under load or acceleration. You may also observe performance issues, increased exhaust emissions, or even a blinking check engine light. Sometimes, these symptoms only surface intermittently, making the issue tricky to pin down.

• Engine misfire (especially noticeable at idle or acceleration)
• Rough running or engine hesitation
• Decreased power or fuel efficiency
• Check Engine Light illuminated (steady or flashing)
• Difficulty starting or extended cranking
• Increased emissions (may fail emissions test)

Most Probable Causes for P0358 #

The causes of P0358 typically center on the ignition system’s electrical components, but can also extend to wiring faults or ECU malfunctions. Below, they’re ordered from most to least frequent:

1. Faulty ignition coil “H” (internal short/open in the coil winding or connector)
2. Damaged or corroded ignition coil wiring harness (open or short circuits in the wiring to coil “H”)
3. Defective ignition coil connector (loose, bent, or corroded pins)
4. Faulty ECM/PCM (rare, but possible if no other faults are found)
5. Blown fuse or relay related to ignition circuit

Step-by-Step Diagnostic for P0358 #

Diagnosing P0358 requires patience and methodical checks. Always start with the simplest solutions—never assume the worst! Here’s a proven process:

• Step 1: Confirm code and clear any existing DTCs. Retest to see if P0358 returns.
• Step 2: Conduct a visual inspection of ignition coil “H” (typically cylinder 8) and its wiring. Look for cracks, burns, or loose connectors.
• Step 3: Swap ignition coil “H” with another cylinder’s coil. If the misfire/code moves, the coil is faulty.
• Step 4: Check the ignition coil connector for bent pins, corrosion, or poor fit.
• Step 5: Test for battery voltage at the ignition coil with the ignition on. No voltage = wiring or fuse issue.
• Step 6: With a multimeter, measure continuity and resistance in the wiring from the ECM/PCM to the coil. Repair as necessary.
• Step 7: If wiring and coil are good, consider ECM/PCM diagnosis (rare—consult OEM procedures).

Possible Repairs for P0358 #

Once you’ve identified the cause, repairs can be straightforward or require more in-depth work. Always use OEM-quality parts for reliability.

• Replace faulty ignition coil “H” (most common solution)
• Repair or replace damaged wiring harness between ECM/PCM and ignition coil
• Clean, tighten, or replace ignition coil connector as needed
• Replace blown fuse or faulty relay in the ignition circuit
• Replace ECM/PCM (very rare; only after confirming all other components are good)

Is It Safe to Drive with Code P0358? #

Limited—It is technically possible to drive short distances with P0358 logged, but it is not recommended. A misfiring cylinder can cause poor engine performance, increased fuel consumption, and in severe cases, damage to the catalytic converter due to unburned fuel. You risk more expensive repairs if you ignore this issue, especially if the check engine light is flashing.

Vehicles Most Commonly Affected by P0358 #

While P0358 can appear on any vehicle with individual ignition coils, it is most often reported on V8 engines from major OEMs. Vehicles with coil-on-plug ignition and direct coil control (common since the late 1990s) are especially susceptible.

• Ford F-150, F-250, and other V8 trucks (2000–present)
• Chevrolet Silverado, Tahoe, Suburban, Camaro V8 models
• Toyota Tundra, Sequoia, and Land Cruiser V8 engines
• Dodge Ram 1500, 2500 (Hemi V8)
• Lexus LS, GS, and LX V8 models

Common Mistakes & Best Practices for P0358 #

A rushed diagnosis can lead to unnecessary parts replacement and frustration. To avoid the most frequent pitfalls, keep these tips in mind:

• Don’t replace all ignition coils “just in case”—identify the faulty one with swaps or testing.
• Always inspect and test connectors and wiring before condemning the ignition coil.
• Clear codes and perform a road test after repairs to ensure the issue is resolved.
• Don’t overlook possible ECM/PCM faults, but only suspect them after confirming all other components.
• Use high-quality, OEM-spec parts to ensure long-term reliability.

Quick FAQ about P0358 #

Is P0358 always caused by a bad ignition coil?
Not always. While a failed coil is the most common cause, damaged wiring, connectors, or even a faulty ECM/PCM can also trigger this code. Always diagnose before replacing parts.

Can I just clear the code and keep driving?
Clearing the code without addressing the root cause means the problem—and the risk of further damage—remains. The code will likely return, and you could face more expensive repairs in the future.