P0362 is one of those ignition-related trouble codes that can be frustrating, but it’s usually very fixable once you understand what’s going on. This code points to a problem with one specific ignition coil circuit, not the entire ignition system. In most cases, you’re dealing with a wiring, connector, or coil issue rather than a bad engine computer. In this guide, you’ll learn what P0362 actually means, the most common causes, symptoms to watch for, how a mechanic would diagnose it, and what repairs typically cost.
What Does P0362 Mean?
P0362 is an OBD-II diagnostic trouble code that stands for “Ignition Coil L Primary/Secondary Circuit Malfunction.” On most vehicles, the letter “L” refers to a specific coil position in the firing order (often coil #12 or the last coil in the sequence, depending on manufacturer). The engine control unit (ECU) has detected an electrical fault in that coil’s control or feedback circuit.
In plain terms, the ECU is seeing voltage or signal values from that coil that are outside the expected range. This could be an open circuit, short to power, short to ground, or a weak signal. The result is usually a misfire on that cylinder, reduced power, and a check engine light.
Quick Reference
- Code: P0362 – Ignition Coil L Primary/Secondary Circuit Malfunction
- Type: Ignition system / electrical fault (specific coil)
- Common Causes: Bad ignition coil, damaged wiring, poor connector, rare ECU fault
- Typical Symptoms: Misfire, rough idle, loss of power, poor fuel economy
- Severity: Moderate to high – can damage catalytic converter if ignored
Real-World Example / Field Notes
In the shop, I see codes like P0362 most often on higher-mileage vehicles or ones that have had previous engine work. A common scenario: the customer complains about a rough idle and flashing check engine light under load. Scan tool shows a misfire on one cylinder and P0362 stored. Visual inspection reveals a coil connector with broken locking tabs or a harness rubbed through on the valve cover. Replacing the coil and repairing the wiring clears the code and restores smooth operation. ECU failures are possible, but they’re rare compared to simple coil or wiring issues.
Symptoms of P0362
- Check engine light on: The MIL will be illuminated, sometimes flashing during heavy misfire.
- Engine misfire: You may feel shaking, stumbling, or a “chugging” sensation, especially at idle or under load.
- Rough idle: The engine may idle unevenly, with RPM fluctuations and vibration in the steering wheel or seat.
- Loss of power: Acceleration can feel weak or hesitant, particularly when climbing hills or merging.
- Poor fuel economy: Misfires waste fuel, so you might notice reduced MPG over time.
- Exhaust odor or popping: Unburned fuel entering the exhaust can cause a strong fuel smell or light popping in the tailpipe.
- Hard starting: In some cases, the engine may crank longer or struggle to start smoothly.
- Possible additional codes: You may see related misfire codes (P030X) stored along with P0362.
Common Causes of P0362
Most Common Causes
- Failed ignition coil: The coil for that specific cylinder (coil “L”) has an internal short or open circuit, causing incorrect primary/secondary voltage.
- Damaged coil connector: Broken locking tabs, spread terminals, corrosion, or moisture in the connector can interrupt the signal.
- Wiring harness damage: Chafed, pinched, or melted wires between the coil and ECU can cause an open circuit or short to ground/power.
- Poor ground or power feed: Shared ignition power or ground circuits with high resistance can trigger this code and others.
- Aftermarket coil issues: Cheap coils sometimes fail early or don’t match OEM specs, causing signal irregularities.
Less Common Causes
- ECU driver failure: The ignition driver circuit inside the ECU for that coil can fail, though this is much less common than a bad coil or wiring.
- Previous engine work errors: Coils or connectors swapped incorrectly, wires stretched or pinched during head gasket or valve cover jobs.
- Water intrusion: Leaking cowl, bad hood seal, or car washes forcing water into the coil area, leading to corrosion and intermittent faults.
- Rodent damage: Mice or rats chewing on ignition wires, especially on vehicles parked outside or stored for long periods.
- Incorrect spark plugs: Wrong plug type or gap can stress the coil and eventually cause internal failure.
Diagnosis: Step-by-Step Guide
To diagnose P0362 properly, you’ll want a basic scan tool, a digital multimeter (DMM), and ideally an automotive lab scope. A wiring diagram for your specific vehicle is extremely helpful. If you don’t have these tools or aren’t comfortable working around ignition components, it’s wise to let a professional handle it.
- Confirm the code and check for companions: Use a scan tool to read all stored and pending codes. Note any misfire codes (P030X) and freeze-frame data (RPM, load, temperature) when P0362 set.
- Visual inspection of coil and wiring: Locate the coil labeled or corresponding to “L” (refer to service info). Check the coil body, connector, and surrounding harness for cracks, burns, oil contamination, or rubbed-through insulation.
- Swap test the coil (if accessible): Swap the suspected coil with another cylinder’s coil. Clear codes and test drive. If the misfire and code move to the new cylinder (e.g., P036X changes), the coil is likely bad.
- Check power and ground at the coil: With the key on (engine off), use a multimeter to verify proper voltage on the coil power feed and good ground. Compare readings to a known-good coil circuit if possible.
- Inspect the signal/control wire: With the connector unplugged and ignition off, check resistance on the control wire between the coil and ECU. Look for open circuits or shorts to ground/power using the wiring diagram.
- Wiggle test the harness: While monitoring live data or using a lab scope on the coil circuit, gently move the harness. If the signal drops out or the engine stumbles, you likely have an intermittent wiring or connector issue.
- Use Mode $06 data (if available): Some scan tools let you view Mode $06 misfire counters. This can confirm which cylinder is misfiring most and help verify your diagnosis.
- Check for ECU output (advanced): With a lab scope, you can view the coil primary waveform commanded by the ECU. A missing or distorted pattern on that channel, with good wiring, points toward an ECU driver fault.
- Inspect spark plugs: Pull the plug from the affected cylinder. Look for fouling, cracks, or incorrect gap that could overload the coil.
- Clear codes and road test: After repairs, clear all codes, then perform a thorough road test under similar conditions to when the code set. Re-scan to confirm P0362 does not return.
Pro tip: Always fix any obvious wiring or connector issues before condemning the ECU. In real-world diagnostics, wiring faults and bad coils outnumber ECU failures by a large margin.
Possible Fixes & Repair Costs
The exact repair for P0362 depends on what the diagnosis finds, but most fixes are straightforward ignition or wiring repairs. Labor time is usually 0.5–2.0 hours unless there’s extensive harness damage.
- Replace ignition coil: The most common fix. Parts typically run $50–$180 per coil depending on brand and vehicle, plus 0.5–1.0 hour labor.
- Repair or replace coil connector: Pigtail connector kits are often $20–$60, with 0.5–1.5 hours labor for cutting, soldering, and heat-shrinking.
- Harness repair: Splicing in new wire sections or repairing chafed areas can range from $80–$300 depending on severity and access.
- Replace spark plugs: If plugs are worn or fouled, a full set can cost $60–$200 plus labor, often combined with coil replacement.
- ECU replacement/programming: Rare, but if needed, you’re typically looking at $500–$1,500+ including programming and setup.
In most shops, you can expect a typical P0362 repair to fall in the $150–$450 range when it’s just a coil and minor wiring work. Costs vary with vehicle make, engine layout, parts quality (OEM vs aftermarket), and local labor rates.
Can I Still Drive With P0362?
You can often still drive with P0362, but it’s not recommended for long. A single-cylinder misfire may feel like just a rough idle or slight loss of power, but every misfire sends unburned fuel into the exhaust. That overheats and damages the catalytic converter over time, which is a much more expensive repair. If the check engine light is flashing, that indicates an active, severe misfire and you should avoid driving except to get to a repair facility. Short, gentle trips only, and no towing or hard acceleration.
What Happens If You Ignore P0362?
Ignoring P0362 can turn a relatively inexpensive ignition repair into a major bill. Continuous misfires can melt or clog the catalytic converter, foul oxygen sensors, and cause long-term engine damage from raw fuel washing oil off the cylinder walls. You’ll also suffer from poor fuel economy and reduced performance. Addressing the problem early is almost always cheaper than waiting.
Related Codes
- P0399 – Ignition Coil “R” Primary/Secondary Circuit
- P0364 – Reserved
- P0363 – Misfire Detected Fueling Disabled
- P0361 – Ignition Coil “K” Primary/Secondary Circuit
- P0360 – Ignition Coil “J” Primary/Secondary Circuit
- P0359 – Ignition Coil “I” Primary/Secondary Circuit
- P0358 – Ignition Coil “H” Primary/Secondary Circuit
- P0357 – Ignition Coil “G” Primary/Secondary Circuit
- P0356 – Ignition Coil “F” Primary/Secondary Circuit
- P0355 – Ignition Coil “E” Primary/Secondary Circuit
Key Takeaways
- P0362 points to an electrical problem in a specific ignition coil circuit, not the entire ignition system.
- Most common causes are a failed coil, damaged wiring, or a bad connector; ECU failure is rare.
- Symptoms include misfire, rough idle, loss of power, and a check engine light (often flashing under load).
- Diagnosis involves visual inspection, coil swapping, checking power/ground, and testing the control wire.
- Typical repairs range from $150–$450 when caught early; ignoring the issue can destroy the catalytic converter.
Vehicles Commonly Affected by P0362
P0362 can appear on any OBD-II vehicle with coil-on-plug or coil-pack ignition, but it’s more frequently seen on certain platforms. Many Ford and Lincoln V6 and V8 engines, especially with coil-on-plug setups, are known for coil and connector issues. GM (Chevrolet, GMC, Cadillac) truck and SUV engines with individual coils can also trigger this code as mileage climbs. Chrysler, Dodge, and Jeep models with multi-coil systems, as well as some BMW, Mercedes-Benz, and Audi engines, are no strangers to ignition coil circuit faults. High-mileage vehicles, those exposed to heat and oil leaks around the valve covers, and cars with previous engine work are most prone.
FAQ
Can P0362 cause serious engine damage?
P0362 itself is an electrical fault code, but the misfires it causes can lead to serious damage if ignored. Long-term misfiring can overheat and ruin the catalytic converter, foul spark plugs and O2 sensors, and wash oil off cylinder walls, increasing wear. Fixing it promptly prevents these issues.
Is P0362 always caused by a bad ignition coil?
No. While a failed coil is very common, P0362 can also be caused by damaged wiring, a loose or corroded connector, poor power or ground supply, or in rare cases a faulty ECU driver. That’s why basic testing and sometimes a coil swap test are important before buying parts.
Can I clear P0362 and keep driving if the car runs okay?
You can clear the code, but if the underlying problem isn’t fixed, it will usually come back. Even if the engine feels mostly normal, intermittent misfires can still damage the catalytic converter over time. It’s better to diagnose and repair the cause than to repeatedly clear the code.
How do I know which coil “L” is on my engine?
The exact coil position for “L” depends on your engine layout and manufacturer. Some service manuals map letters to cylinder numbers; others use firing order. The safest approach is to consult a factory service manual, a reliable repair database, or a wiring diagram that shows the coil labeling for your specific year, make, and model.
Can a bad spark plug trigger code P0362?
An incorrect or failing spark plug won’t directly cause P0362, but it can stress the ignition coil and lead to coil failure, which then triggers the code. If you’re replacing a coil on a high-mileage engine, it’s often smart to inspect and replace the spark plugs at the same time to prevent repeat issues.