2004 Jeep Wrangler 4.0L Engine P0351 Multiple Misfires - Diagnosis & Fix Guide
While driving my 2004 Jeep Wrangler 4.0L, the vehicle suddenly lost power, the check engine light began flashing, and it entered limp mode. I managed to drive it to work and used an OBD2 scanner to identify code P0351 — indicating a multiple misfire due to ignition coil failure. I replaced both the ignition coil pack and spark plugs, but the issue persists. My friend mentioned that the camshaft synchronizer sensor has excessive play and suggested it might be causing the problem. However, I'm unsure if this is relevant since no diagnostic code is reported for the cam position sensor. I also want to know which specific pins on the Powertrain Control Module (PCM) should be checked when troubleshooting wiring issues related to the ignition coil. Additionally, a new connector is arriving as a precaution. Could someone confirm whether P0351 is the only code present or if there are any underlying misfire codes like P030x? Any guidance on proper testing procedures (e.g., key-off-on checks) and wiring diagnostics would be greatly appreciated.
You're scanning — I'm not convinced the 'key-on-off' trick works for all codes. Is P0351 the only code reported, or are there also misfire codes like P030x? Leave the camshaft position sensor (CMP) alone for now — if no code is present, it's unlikely to be the root cause. Regarding wiring diagnostics: There are four wires connected to each ignition coil. When the key is off, only one wire should have voltage (typically DK/ORG). The other three are signal/control circuits. To test: - Unplug the connector with the key OFF and verify no voltage on the signal wires. - With the key ON but engine off, ensure there's no ground on those three control/signal wires. - Gently shake the harness near the cylinder head area — some wires may rub or wear through in this region. I believe the three control wires are tan with a tracer. Note: Jeep engines are sensitive to spark plugs and aftermarket ignition coils, which can sometimes cause intermittent misfires. Consider using OEM-quality components if possible.