P0358 — Ignition Coil H Primary/Secondary Circuit Malfunction

What does P0358 specifically identify?

P0358 identifies a detected electrical fault in the ignition coil H primary or secondary circuit. It may involve the coil, connector, wiring, power feed, spark plug, or ECU driver rather than only the coil itself.

Is P0358 the same as a misfire code?

No. P0358 is a circuit-monitoring code, although it may be stored alongside a cylinder misfire code. The scan data should be checked for additional information because the underlying misfire may be affecting the cylinder served by coil H.

Can the vehicle be driven with P0358?

Limited driving may be possible if there is no severe shake or loss of power, but continued operation with an active misfire can damage the catalytic converter. Avoid heavy acceleration and have the ignition circuit inspected promptly.

Where is ignition coil H located?

The H designation identifies a particular ignition output, but it does not always mean cylinder 8 on bank 1. Consult the engine-specific wiring diagram and cylinder layout before testing or replacing the coil.

The engine control unit continuously evaluates the performance of every ignition coil in your vehicle, firing them in a precise sequence to maintain smooth combustion. When the module sends a command signal to the ignition coil labeled "H" — typically the eighth cylinder in firing order — it expects a corresponding confirmation signal back through the primary circuit. P0358 triggers when that confirmation never arrives or falls outside acceptable parameters during consecutive drive cycles. Unlike codes that point to a specific open or short circuit, this one tells you something is wrong with the coil's ability to receive commands or report back, whether the problem lives inside the coil itself, in its wiring, or in the ECU driver that controls it.

Because P0358 covers both primary and secondary sides of the ignition circuit, the fault could stem from a failed driver inside the computer, a broken wire in the harness, a cracked coil housing, or degraded insulation allowing moisture to seep in. The ECU does not guess which component is at fault — it simply logs that the expected behavior did not occur. That is why freeze frame data saved alongside the code is valuable: it records RPM, engine load, coolant temperature, and vehicle speed the moment P0358 set, giving you the exact conditions to replicate during diagnosis.

The Check Engine Light appears only after the ECU validates the fault across multiple drive cycles, confirming it is a persistent rather than momentary condition. If the light flashes, the situation is more urgent, indicating an active misfire that can damage emissions components. Regardless of whether the light is solid or flashing, P0358 means cylinder number eight is not firing correctly, and the underlying cause should be identified before the problem spreads.

Symptoms of P0358

The symptoms you experience with P0358 depend on how severely cylinder eight is misfiring and whether the ECU has altered fuel delivery or transmission shifting to compensate.

• Jerking or stumbling under acceleration as the engine struggles to maintain power without a properly firing cylinder
• Reduced overall power especially when climbing hills or towing, because the engine is effectively running on seven cylinders
• Rough idle or noticeable vibration when stopped, since one cylinder is contributing nothing to idle quality
• Hard starting particularly in humid or rainy conditions when moisture can worsen an already compromised ignition circuit
• Elevated fuel consumption as the ECU attempts to compensate for the misfire by adding fuel, and unburned fuel passes through the exhaust
• Check Engine Light illuminated on the dashboard, and potentially flashing if the misfire is severe and continuous
• Misfires occurring at any speed though they are often most noticeable under load or during rapid throttle transitions

Common Causes of P0358

The most frequent culprits behind P0358 are also the least expensive to fix, which is why a systematic approach pays off before spending money on major components.

• Damaged wiring or connectors at the coil harness, including corroded terminals, broken insulation, or loose plugs that interrupt the command or ground signals
• Faulty ignition coil on cylinder eight — either an internal winding failure in the primary circuit or a cracked housing allowing spark leakage
• Moisture or oil contamination in the spark plug well, which can bridge voltage to ground before it reaches the plug
• Worn or incorrectly gapped spark plugs that cannot receive or translate the coil's output into a usable spark
• ECU driver failure or software calibration issue where the module itself cannot send or receive signals properly on this specific circuit
• Short or open circuit in the primary control wire between the ECU and ignition coil
• Coil pack failure if your vehicle uses a multi-cylinder pack where one section has failed internally

How to Diagnose P0358

A logical sequence prevents unnecessary parts replacement and pinpoints the exact cause without guesswork.

1. Connect an OBD2 scanner and confirm P0358 is stored. Record the freeze frame data — this shows exactly what the engine was doing when the fault occurred, including RPM, load, temperature, and speed. Replicate these conditions during your road test after repairs to verify the fix.
2. Pull all stored codes and address any related P0300 through P0308 codes first. Misfire codes for other cylinders may point to a shared ground or power issue. Also search for manufacturer TSBs related to your specific make, model, and year — some ignition coil failures have factory-issued service bulletins or software updates.
3. Perform a visual inspection of the wiring harness for cylinder eight. Look for chafed wires near heat sources, broken strands at connector pins, corrosion buildup, and ensure the connector clicks securely into the coil. Wiggle the harness while monitoring live data on the scanner to see if the signal drops out.
4. Swap the ignition coil to a different cylinder if your vehicle uses individual coils. If the fault code migrates to a different cylinder position, you have confirmed a bad coil. If P0358 stays with cylinder eight, the problem is upstream in the wiring or ECU.
5. Test primary circuit voltage and ground at the coil connector with a multimeter. The ECU should provide a switched ground signal on the command circuit when cranking or running. No signal indicates a wiring break or failed ECU driver; a constant signal suggests the ECU is stuck.
6. Remove and inspect spark plugs for cylinder eight. Check the gap against factory specifications, look for oil fouling, carbon deposits, or wet plugs indicating fuel or coolant leaks. Replace plugs if worn or outside tolerance.
7. Clear the code and perform a complete drive cycle including the conditions from the freeze frame data. If P0358 does not return after several drive cycles under similar load and temperature, the repair is complete.

Repair Options and Costs

Depending on what your diagnosis reveals, the repair may involve anything from connector cleaning to full coil replacement.

• Replace the ignition coil on cylinder eight: $150–$380 for parts and labor at an independent shop. OEM coils from the dealership cost more but ensure exact fitment; aftermarket coils are less expensive but verify they meet or exceed original specifications.
• Repair damaged wiring or connectors: $80–$250 depending on whether you need a terminal repair kit, a new harness section, or a complete connector replacement. Soldered and heat-shrunk repairs last longer than splice connectors.
• Replace spark plugs: $90–$250 for eight plugs including labor. If the plugs are heavily fouled, address the root cause — such as oil from a leaking valve cover gasket — before installing new ones.

How Much Does Fixing P0358 Cost Overall?

Most P0358 repairs fall between $80 and $380 total. The exact figure depends entirely on what is faulty. Wiring repairs and connector cleaning sit at the lower end, while a full ignition coil replacement plus spark plugs pushes toward the upper range. ECM replacement or harness replacement — rare but possible — can exceed $1,000 when labor and programming are factored in.

The cheapest fix is rarely the right first step only if you skip diagnosis entirely. A technician who visually inspects wiring and tests circuits before quoting a repair will almost always save you from replacing parts that were not actually broken.

Can You Drive with P0358?

Drive with caution and seek repair promptly. A cylinder eight misfire caused by P0358 allows unburned fuel to enter the exhaust stream, where it ignites inside the catalytic converter. That extra heat can melt the catalyst substrate, turning a relatively simple ignition problem into an exhaust system failure that costs $1,000 or more to fix. If the Check Engine Light is flashing rather than solid, stop driving immediately and have the vehicle towed — continued operation risks permanent damage to the converter and potentially the engine from pre-ignition or raw fuel entering the oil sump. Even with a solid light, limit hard acceleration and heavy loads until the fault is resolved.

Related OBD2 Codes

• P0300: Random/Multiple Cylinder Misfire Detected
• P0301: Cylinder 1 Misfire Detected
• P0302: Cylinder 2 Misfire Detected
• P0303: Cylinder 3 Misfire Detected
• P0304: Cylinder 4 Misfire Detected
• P0305: Cylinder 5 Misfire Detected