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2003 Dodge Ram 5.9L Gas Engine Misfire & Emission Codes: P0300, P0302, P0308, P0442, P0455 Explained

Model: Dodge 5.9 Fault Code: P2177 Posted: 2006-12-19 17:41

I recently purchased a code reader and discovered several trouble codes on my 2003 Dodge Ram 5.9L gasoline engine: P0300 (Random Multiple Cylinder Misfire Detected), P0302 (Cylinder #2 Misfire Detected), P0308 (Cylinder #8 Misfire Detected), P0442 (Small Evaporative Emission System Leak Detected), and P0455 (Large Evaporative Emission System Leak Detected). I'm wondering if the misfire codes are directly related to the emission system leaks. The engine runs smoothly under normal conditions, but the check engine light has been on intermittently. The misfires appear to be occurring across multiple cylinders, which may suggest issues with ignition components or fuel delivery. Meanwhile, the evaporation leak codes point to potential problems in the fuel vapor system—such as a loose or damaged hose near the intake manifold. I'm looking for clarity on whether these misfire and emission codes are connected, and what steps I should take next to diagnose and resolve them.

Related fault codes

P2177

Comments (5)

Anonymous 2006-12-19 17:58

It's highly unlikely that the misfires are directly caused by the evaporation system leaks. A significant vacuum leak would be required—something rare in this setup—and even then, it typically affects specific cylinders rather than multiple random ones. The vehicle is a 2003 Dodge Ram, likely a 1500 model with a 360ci V8 engine.

Anonymous 2006-12-20 16:08

Thanks for the input! I'm currently checking components starting from the spark plugs and working backward through the ignition coils and distributor. My truck is a 2003 Ram 1500 with a 360ci V8 gasoline engine. I've upgraded the intake system with a throttle body spacer, Street & Performance Intake, Gibson cat-back exhaust, and a Ram Air hood that feeds directly into an AFE filter. I'm about to install Gibson shorty headers coated with Polydyne and will soon add a performance programmer. Fuel efficiency improved from 11–13 mpg to 13–17 mpg after these modifications.

Anonymous 2006-12-20 16:34

Were there any trouble codes present before the recent intake and exhaust upgrades? Could the changes have triggered or exacerbated existing issues?

Anonymous 2006-12-21 08:30

Most of the modifications were installed in early 2003. The check engine light first appeared in spring, and I found a vacuum leak beneath the cold air intake canister connected to the intake manifold vacuum hose. After disconnecting the battery for ten minutes, the light turned off—though it has recently come back on. The truck runs fine otherwise. My current plan is to inspect the spark plugs first, then clear the codes to see if any new ones appear. I'm still learning how to use a code reader effectively. Did disconnecting the battery erase the codes? Is there a way to determine when the codes were generated? My current device doesn't support this feature. Thanks, Mark.

Anonymous 2006-12-21 08:41

Disconnecting the battery likely cleared the stored codes. How old are your spark plugs? Worn or degraded plugs could be a contributing factor to misfires, especially in older engines like this one.