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2002 Jeep Liberty 3.7L V6 P0302, P0201, P0203, P0205 - Rough Idle, Hard Start, and Misfire Diagnosis

Model: 2002 Jeep Liberty Fault Code: P0201 Posted: 2010-04-19 14:29

Hi everyone, I'm having a serious issue with my 2002 Jeep Liberty 3.7L V6 engine (145,000 miles). It was running fine until recently when it started running rough, especially under load or at idle. The car is hard to start when hot and loses power completely during driving. A scan tool revealed multiple fault codes: P0302 (misfire in cylinder 2), P0201, P0203, and P0205. I initially replaced the spark plugs due to the P0302 code, but after that, the symptoms worsened. The engine now runs unevenly, nearly stalls at stoplights, and feels unstable. I understand that P0302 indicates a misfire in cylinder 2, while P0201, P0203, and P0205 point to potential fuel injector failures—specifically on the same side of the engine. My question is: Why are three injectors on one bank showing faults? Is this a wiring issue, a sensor problem (like TPS), or something more serious like a faulty PCM or fuel pump? What should I check first? I'm looking for clear, actionable steps to diagnose and fix this. Any experience with 2002 Jeep Liberty V6 engine misfires or injector codes on one side of the engine would be greatly appreciated.

Related fault codes
P0201P0203P0205P0302
Comments (12)
Anonymous 2010-04-19 15:36

A failing Throttle Position Sensor (TPS) is a common cause of fuel injector-related fault codes like P0201, P0203, and P0205 on the 2002 Jeep Liberty. While misfires are typically linked to cylinder issues, TPS faults can trigger false injector error codes. To verify this, try unplugging the TPS and monitoring live data via an OBD-II scanner. If the codes disappear or improve, it's likely a bad TPS. Always check wiring harnesses first—especially around the engine bay—before replacing parts.

Anonymous 2010-04-19 16:49

Thanks for that insight! I'm wondering if replacing just the TPS would fix all three injector codes on one side of the engine? Would a faulty TPS affect only one cylinder or spread across multiple injectors? My boyfriend is helping me troubleshoot—any advice on where to start?

Anonymous 2010-04-19 17:36

We removed and reconnected the TPS, and after that, all the injector-related codes (P0201, P0203, P0205) cleared. The only remaining code is now P0123. Based on this, I believe a new OEM dealer-grade TPS should resolve the underlying issue. Does anyone confirm if replacing the TPS fixes both misfire and injector problems in this model?

Anonymous 2010-04-19 18:48

While I can't verify without seeing the vehicle with live data, trying a known-good OEM dealer TPS is a reasonable first step for your 2002 Jeep Liberty. If the issue persists after replacing the sensor, consider using a professional scan tool to check for underlying wiring faults or misfire monitoring patterns.

Anonymous 2010-07-27 19:52

Hi there—my 2004 Jeep Liberty 3.7L V6 also shows P0201, P0203, and P0205 codes. I'm experiencing similar symptoms: rough idle and poor engine performance. Any suggestions on how to diagnose this? Is it likely a TPS issue or something else?

Anonymous 2010-07-27 19:55

I’ve resolved the issue with my 2002 Jeep Liberty by replacing the TPS. After that, all codes cleared and engine performance improved significantly. I’d recommend trying this fix first before moving to more expensive repairs.

Anonymous 2010-07-28 05:10

Have you tried checking wiring connections or using a scan tool with live data? In addition to TPS, other common causes include faulty fuel injectors, poor ground connections, or degraded engine control signals. A full diagnostic with OBD-II data would help pinpoint the root cause.

Anonymous 2010-07-28 13:42

I replaced the PCM, MAP sensor, and spark plugs—still experiencing poor performance and P0201 and P0203 codes. It seems like a persistent wiring or sensor issue rather than just a component failure. Any thoughts on what else to check?

Anonymous 2010-07-28 16:40

The most likely causes are either a faulty TPS or a wiring harness problem—especially in the engine bay area. Always use an OEM dealer-grade TPS when replacing it. If you're unsure who performed the repairs, make sure they have proper diagnostic tools and experience with this model.

Anonymous 2010-07-28 17:05

I have some mechanical knowledge but am not a certified mechanic. I had the PCM installed by a technician who specialized in this vehicle. I’ll start by inspecting all wiring connections before replacing any components. Thanks for the advice!

Anonymous 2012-12-09 14:37

This is exactly what happened with my 2002 Jeep Liberty—same symptoms and codes. After replacing the TPS, the issue resolved completely. What was your exact solution? Did you replace just the TPS or did it require additional work?

Anonymous 2012-12-10 09:52

Lukesdyer — please start a new topic with full details: year, make, model, engine type, transmission, known history, drivability issues, and all active codes. This thread is outdated—let’s keep discussions focused and actionable for others facing the same issue.