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P0171 Code on 1997 Dodge Intrepid: Fuel System Running Lean Bank 1 - Diagnosis and Fixes

Model: 1997 Dodge Intrepid Fault Code: P0171 Posted: 2006-11-25 15:00

I'm seeking help with a persistent P0171 code on my 1997 Dodge Intrepid with a 3.5L 24-valve engine. I've been struggling to pass emissions tests, and the issue has evolved over several repairs. The problem began after replacing the oxygen sensor, followed by another O2 sensor, and then an EGR system—after which everything seemed fine for about a week. However, just before my scheduled inspection, the overdrive clutch plate failed, requiring a $1600 transmission rebuild. After that repair, I waited another week to retest. On the day of the inspection, as the mechanic was pulling the car into the bay, the check engine light came back on with code P0171: 'Fuel system running lean - Bank 1'. I initially suspected an air leak and replaced the PCV valve. I then discovered a loose intake manifold bolt, so I replaced the pendulum gasket, intake manifold gasket, fuel rail gaskets, and one injector that appeared damaged. After reassembly, I thought the issue was resolved. However, when I started the car and let it run, the P0171 code returned. This indicates my fix wasn't sufficient. A mechanic suggested a faulty O2 sensor, but I recently replaced both O2 sensors on the driver's side (Bank 1). My vehicle does not have a MAF sensor—only a MAP sensor. I tested the intake air temperature (IAT) sensor: at cold conditions, resistance is around 3000 ohms (within normal range), but at hot conditions it reads about 2000 ohms. The specification for hot operation should be between 20–170 ohms—this reading is significantly off. I plan to replace the sensor tomorrow, though I'm unsure if this could be the root cause. I've also checked for exhaust leaks and found none. Next steps include checking fuel pressure—I suspect a failing fuel pump, but I'm uncertain whether it would affect both banks or only one. I feel overwhelmed and am seeking clear technical guidance on how to resolve this P0171 issue with my 1997 Dodge Intrepid. Any insights into possible causes or diagnostic steps would be greatly appreciated.

Related fault codes
P0171
Comments (3)
Anonymous 2006-11-25 15:07

I also performed a brake-klean inspection around the intake manifold and pendulum area, and there was no noticeable change in engine RPM during the test—this rules out significant air leaks from those regions.

Anonymous 2006-11-27 16:03

I replaced the intake air temperature sensor, but the P0171 code persisted. I only have a basic OBD-II code reader and observe that LTFT1 is +24, STFT1 is +24, while LTFT2 and STFT2 fluctuate between -2 and +4. When I unplugged the upstream O2 sensor on Bank 1, the ECU reported 'no activity' for that sensor, but also triggered a code indicating both Bank 1 and Bank 2 are lean. This is unusual—why does Bank 2 show a lean condition only when Bank 1's upstream O2 sensor is disconnected? I'm confused about this behavior and would appreciate any explanation or insight from experienced mechanics. Thank you, AJ.

Anonymous 2006-11-27 16:42

Check your fuel pressure—it could be a failing fuel pump or delivery issue, especially since the P0171 code indicates lean conditions on Bank 1. A drop in fuel pressure might explain the lean reading even if only one bank is affected due to sensor feedback loops or miscommunication between sensors and ECU.