Honda P1399 Code – What It Means and How to Fix It

Ever had the P1399 code flash on your Honda’s dashboard and wondered what on Earth it means? You’re about to find out.

If you’re a Honda owner, P1399 might be an all-too-familiar sight on your vehicle’s dashboard. A code that’s peculiar to Honda vehicles, it rings alarm bells about random cylinder misfires. These misfires aren’t just minor inconveniences.

They can lead to a range of issues from your car stuttering on the highway to it guzzling more gas than usual. Don’t fret, though. By the end of this guide, you’ll understand this code inside out and have a step-by-step strategy to tackle it.

What is the Honda P1399 Code?

What is the Honda P1399 Code?

So, what does the P1399 code really mean? Exclusive to Honda vehicles, this manufacturer-specific trouble code is your car’s way of saying there’s a random misfire somewhere in those cylinders. But what’s a misfire?

Think of it as a hiccup in your engine. When a spark plug fails to light up the air-fuel cocktail in a cylinder, the result is incomplete combustion. And this, my friend, translates to power loss.

Your car’s engine control module (ECM) is like its nervous system. It’s constantly keeping tabs on the engine speed and relies heavily on the crankshaft position sensor (CKP) to get a pulse on misfires.

Spotting a misfire is like finding a needle in a haystack for the ECM, but with the CKP’s help, it’s possible. A misfire causes engine speed variations, altering the CKP signal. When this happens, your trusty ECM pops up the P1399 code and, for added drama, illuminates the check engine light.

And here’s a bonus tidbit: the P1399 code seldom parties alone. It’s often seen mingling with other codes like P0300 (the generalist misfire code), P0301 (indicating cylinder 1 has issues), P0302 (pointing fingers at cylinder 2), and the list goes on.

What Causes the P1399 Code?

When you’re trying to understand what’s behind the P1399 code, it’s a bit like peeling back layers of a complex story. Each potential cause has its narrative. Let’s dive into the world of Honda engines and decipher these tales.

The Saga of Spark Plugs and Wires

The story often starts with the spark plugs. These tiny heroes are tasked with creating the essential spark that brings the air-fuel mixture to life in the cylinders. By their side are the spark plug wires, ensuring this vital spark is delivered right on cue.

However, age, damage, or even corrosion can affect their performance. When these vital components are not in their prime, the spark can be weak or inconsistent, leading to those dreaded misfires. A thorough inspection often unravels the truth behind their condition.

The Ignition Coil Chronicles

Enter the ignition coil, a pivotal character in our engine tale. Its job is rather grand – it transforms the modest voltage current from the battery into a high-powered force fit for the spark plugs.

But, like all heroes, it has its vulnerabilities. Internal shorts, wear, or even an outright failure can weaken its ability to deliver. This results in erratic or insufficient sparks, and before you know it, misfires become the order of the day.

Fuel Injectors: The Sprayers of Balance

Fuel injectors play a role that’s all about balance. Their mission? To spray just the right amount of fuel, ensuring a harmonious blend with air for combustion. However, challenges like clogs, leaks, or malfunctions can tip this balance, causing too much or too little fuel to enter the scene. Misfires can often be the outcome of these imbalances.

EGR Passages: The Silent Guardians

The EGR system is a silent guardian of the environment, designed to minimize harmful NOx emissions. But over time, carbon deposits might settle in, blocking these passages. This obstruction affects the engine’s performance and can be another chapter in the P1399 saga.

Valves: The Rhythm Keepers

Lastly, we have the valves, maintaining the rhythm of intake and exhaust. But if their clearance isn’t set right, the engine’s performance can dance out of sync, resulting in misfires.

How to Diagnose the P1399 Honda Code?

Detecting the root of the P1399 code is akin to piecing together a puzzle. Here’s a step-by-step guide to help you play detective:

1. Code Scanning Session

Kick things off by connecting your OBD2 scanner to the vehicle’s diagnostic port. Fire up the ignition and let the scanner do its magic. Any codes that pop up, especially misfire-related ones, need to be noted.

Useful hint: This guide might provide additional insights into Honda-specific issues.

2. Test Drive Time

After noting down the codes, it’s essential to clear them using the scanner. Now, it’s time for a test drive! Be observant – does the check engine light make a comeback? Do you feel any symptoms like rough idle or loss of power?

3. Spotlight on Spark Plugs and Wires

If the code reappears, turn your detective gaze to the spark plugs and wires. Look for wear, damage, or fouling. Tools like a spark plug tester can be a great ally here.

4. The Ignition Coil Investigation

No issues with the spark plugs or wires? Then, the ignition coil needs to be under the spotlight. Inspect it for any damage or signs of malfunction.

5. Fuel Injector’s Health Check

Now, divert your attention to the fuel injector. Is it clogged or malfunctioning? A noid light can be of great assistance here.

6. EGR Passage Cleanup

If all else seems fine, the EGR passages might be the culprits. A thorough cleanup can often solve the mystery.

7. Valve Clearance Calibration

Lastly, ensure that the valve clearance is in line with the manufacturer’s specifications. If you’re uncertain about this, seeking professional help is recommended.


1. What exactly is the P1399 code?

The P1399 code is a Honda-specific trouble code signaling a random cylinder misfire. This misfire can affect the overall performance of your engine, leading to issues like reduced fuel efficiency and increased emissions.

2. How will I know if my vehicle has the P1399 issue?

You’ll often notice the check engine light illuminated on your dashboard. Additionally, your Honda might exhibit symptoms like a rough idle, hesitation during acceleration, decreased fuel efficiency, or even noticeable jerks when driving.

3. Are spark plugs often the main culprit?

While faulty spark plugs or their accompanying wires are common culprits, they’re not the sole cause. Issues can also arise from a failing ignition coil, clogged fuel injector, blocked EGR passages, or incorrect valve clearance.

4. Is it safe to drive my Honda with the P1399 code?

While your vehicle might still be operational, driving with a misfiring cylinder can lead to further damage, increased emissions, and a reduction in fuel efficiency. It’s advisable to address the issue promptly.

5. How can I diagnose the P1399 code at home?

With an OBD2 scanner, you can read the specific codes causing the check engine light to activate. However, diagnosing the root cause might require further inspection of engine components or even specialized tools. If unsure, it’s best to consult a mechanic.

6. Is the P1399 code exclusive to Honda vehicles?

Yes, the P1399 code is manufacturer-specific and exclusive to Honda vehicles.

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