2005 Jeep Liberty 3.7L with P0171 and P0172: Lean Bank 1, Rich Bank 2 - What's Next?
I recently completed a major overhaul on my 2005 Jeep Liberty 3.7L engine, including replacement of the cylinder heads, timing chain set, spark plugs, air filter, and PCV valve. The vehicle is now running smoothly with no noticeable performance issues. However, two diagnostic trouble codes persist: P0171 (Bank 1 lean) and P0172 (Bank 2 rich). I've already inspected the intake manifold for vacuum leaks and confirmed there are none. I also cleaned the MAP sensor, though I'm now questioning whether this was a wise step given that MAP sensor cleaning is not typically recommended. Given the conflicting readings—lean on Bank 1 and rich on Bank 2—I'm considering replacing the upstream O2 sensor on Bank 1. What would be your next steps? Are there any other diagnostic tools or data points I should check, such as fuel trim values? Any insight into whether the O2 sensors might be stuck in a biased reading (one showing lean, one rich) would be greatly appreciated.
I'm assuming you replaced the cylinder heads due to known valve sealing issues common in Jeep Liberty models. Have you checked for any prior fuel control-related codes before this repair? Cleaning a MAP sensor is generally not recommended and could potentially lead to misdiagnosis. It's particularly puzzling that one bank shows a lean condition (P0171) while the other reads rich (P0172). Could you provide any fuel trim data from your scan tool? While new dealer-installed O2 sensors might seem like a good maintenance step, it's worth noting that both sensors could be stuck in biased readings—especially if they're not properly calibrated or have degraded over time. This imbalance may point to deeper issues such as fuel delivery inconsistencies or sensor failure.