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PO171 Fault Code on 2000 Dodge Dakota 4.7L: Diagnosis and Fixes

Model: Dakota Fault Code: P0171 Posted: 2007-03-21 21:21

I've been troubleshooting my 2000 Dodge Dakota 4.7L for over five days and am still struggling to resolve the PO171 fault code — 'System Lean Bank 1'. Initially, the vehicle showed two codes: one for a slow-response oxygen sensor and another for a lean condition in bank 1. I successfully fixed the O2 sensor issue by replacing it and tightening loose spade connectors that were previously installed by a prior repair shop. Since then, I've tested all sensors and found them to be functioning properly. I've also inspected the intake manifold for leaks using WD40 with no success. The truck is currently running extremely poorly — achieving only 6 MPG in city driving and producing heavy black smoke from the exhaust. When I shine a flashlight into the tailpipe, visible carbon crumbs are clearly visible, indicating severe combustion issues. I've already replaced the oil, spark plugs (which were worn), cleaned the idle air control valve, and verified that the throttle position sensor (TPS) is working correctly. Tonight, I jacked up the MAP sensor for testing and plan to replace it tomorrow — though this will remain a learning experience. At this point, I'm considering cleaning the fuel injectors as a next step, but I'm uncertain whether this would resolve the underlying issue or simply mask symptoms.

Related fault codes
P0171
Comments (12)
Anonymous 2007-03-22 09:55

What is your fuel pressure reading? Has the O2 sensor fault code been resolved? Does your Dakota have an EGR system? Some 4.7L engines are equipped with one.

Anonymous 2007-03-22 11:47

I've tested the fuel pressure and it reads consistently at 48 psi — within the factory specification range of 44.2 to 54.2 psi, with no drop when the engine is off or under load.

Anonymous 2007-03-22 12:37

I've encountered aftermarket oxygen sensors on some Dodge models that can trigger a PO171 code due to poor responsiveness — these units may not respond quickly enough to maintain accurate air-fuel ratio readings. Does your truck have an EGR valve? Could timing chain misalignment be contributing to the lean condition?

Anonymous 2007-03-22 16:54

I plan to swap fuel injectors between bank 1 and bank 2 to see if the PO171 code moves to bank 2. If it does, this would indicate a faulty injector; if not, the issue may lie elsewhere.

Anonymous 2007-03-22 18:59

Nice post — clear troubleshooting steps and detailed observations.

Anonymous 2007-03-23 08:37

Note: The truck has only two oxygen sensors, not three, as some older models may have.

Anonymous 2007-03-23 16:24

Correct — the vehicle is equipped with only two O2 sensors.

Anonymous 2007-03-24 07:11

If there are only two oxygen sensors on a V-style engine, swapping injectors between banks won't generate a PO175 code because bank 1 always has an O2 sensor ahead of the catalytic converter. A PO175 code would only appear if the fuel rail is obstructed — and even then, it wouldn’t necessarily show up after injector swap. This means the test may not detect a faulty injector.

Anonymous 2007-03-24 11:41

That's exactly what I hoped to see — but unfortunately, no code change occurred. It’s disappointing.

Anonymous 2007-03-24 14:43

Could the EGR system or oxygen sensor readings be contributing to this issue? As previously asked, does your truck have an EGR valve?

Anonymous 2007-03-24 15:19

The O2 sensor fault has already been resolved and is no longer present.

Anonymous 2007-03-26 07:19

I understand the issue — could you please share details about the specific repair method, parts used, and any diagnostic tools employed during your work on this vehicle? This would be helpful for others facing similar problems.