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2001 Jeep Wrangler 4.0L A/T DTC P0300, P03-05, P0306: No Start to Misfire After Crank Sensor Replacement

Model: 2001 jeep wrangler Fault Code: P0300 Posted: 2013-02-18 23:39

I own a 2001 Jeep Wrangler with a 4.0L engine and 3-speed automatic transmission (stock, no modifications). The vehicle initially failed to start, which led me to replace the crankshaft position sensor (CPS) at AutoZone. After replacement, the vehicle started and ran smoothly. However, shortly thereafter, when driving at highway speeds above 3000 RPM, the check engine light illuminated. A scan of the powertrain control module (PCM) revealed persistent diagnostic trouble codes: P0300 (random/multiple cylinder misfire), P0305 (cylinder 5 misfire), and P0306 (cylinder 6 misfire). I have since replaced all spark plugs, verified compression across all cylinders, swapped the injectors between cylinders #1 and #6 for testing, and cleaned the fuel injectors. Despite these steps, the issue persists. While I've reviewed several online discussions on this specific fault pattern, no definitive solution has been found. The problem appears to be related to post-replacement engine behavior after installing a new CPS, but I'm seeking expert insight into potential root causes and troubleshooting steps.

Related fault codes
P0300P0305P0306
Comments (4)
Anonymous 2013-02-19 09:33

Always begin with fuel pressure testing when diagnosing misfires. While you've replaced components, consider using OEM parts to avoid compatibility issues. Spark plugs—try switching from Champion to NGK if the issue persists. If that doesn't resolve it, focus on fuel pressure diagnostics. Additionally, a recent tip from my colleague suggests checking the wiring harness at the rear of the cylinder head; this area is prone to chafing and can cause intermittent misfires.

Anonymous 2013-02-25 18:43

If no misfires were present before replacing the crankshaft position sensor, it's highly likely that your aftermarket CPS has an incorrect air gap, which could be causing the misfire. I strongly recommend using original equipment manufacturer (OEM) parts for all engine-related components—including sensors and spark plugs—to ensure proper fitment and function.

Anonymous 2013-05-11 05:30

Ripper—did you ever find a solution to this issue? I'm experiencing the exact same symptoms. My original CPS was also aftermarket, so I’m considering replacing it again to rule out that as the root cause.

Anonymous 2013-05-11 08:24

gator13—consider starting a new topic for better visibility and engagement. More community members will see your post, and sharing detailed information increases the chances of receiving helpful responses.