How is fault code P0308 fixed?

A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training. 1. Pull the live data and the freeze frame so you can see whether the misfire happens cold, hot, at idle, or under load. That alone narrows it down fast 2. Check the misfire counter per cylinder if your tool reads it. A count climbing only on cylinder 8 confirms it's isolated and not a general P0300 3. Swap the coil from cylinder 8 onto a known-good cylinder, then clear the code and drive it. If the misfire moves with the coil, you've found it. Do the same with the plug if the coil checks out 4. Look closely at the plug, boot, and connector on cylinder 8 for cracks, oil, soot, or corrosion before you spend on parts 5. Check the injector is firing and the wiring is clean if ignition swaps come up empty 6. Run a compression or leak-down test on cylinder 8 last, once ignition and fuel are ruled out. Low compression means the problem is inside the engine and the bill changes completely

Cylinder 8 Misfire Detected

Jump to the fix

Severity

High

Can I keep driving?

Avoid extended driving; visit a service soon.

First step

A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training. 1. Pull the live data and the freeze frame so you can see whether the misfire happens cold, hot, at idle, or under load. That alone narrows it down fast 2. Check the misfire counter per cylinder if your tool reads it. A count climbing only on cylinder 8 confirms it's isolated and not a general P0300 3.

PPowertrain
0Generic code
3Ignition / Misfire
08Sequence number

What does it mean?

A misfire is just what it sounds like; a cylinder that is not firing as it should. The P0308 code is caused by a misfire on the number eight cylinder. The Misfire monitor diagnostic is based on variation in crankshaft velocity. The PCM determines this information using the crankshaft position sensor and camshaft position sensor. A misfiring cylinder slows down momentarily, so by monitoring the cam and crank sensor signals, the PCM can calculate when a misfire occurs.

A P0308 code tells you only that a misfire has been detected, not WHY the cylinder is misfiring. That’s why with this code, a thorough diagnosis is mandatory. Misfire Monitor Different manufacturers implement OBD-II requirements slightly differently. The misfire monitor is an OBD-II procedure which identifies a misfire. The misfire monitor is a “continuous” monitor; it is always checking the crankshaft position sensor for a misfire.

It is important to note that the misfire monitor is very reliant on the crankshaft position sensor signal. A faulty crankshaft position sensor will misdiagnose misfires! More information on the other systems involved in a misfire can be found in the background section of codes P0300 and P0301.

Symptoms

Likely causes

How to fix it

Codes From the Same System

All Fault Codes

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This information follows the generic OBD-II definition and does not replace a vehicle-specific diagnosis. The severity rating is rule-based; an authorised diagnostic reading is required for a definitive answer.