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2019 Dodge Journey SXT - P0171 Lean Code, Rough Idle

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Mike T. · rep 0 · May 25, 4:14 AM · 1 replies · solved · Question

Vehicle: 2019 Dodge Journey SXT

My 2019 Dodge Journey SXT with the 2.4L engine just threw a Check Engine Light, and when I scanned it, I got a P0171 code: System Too Lean (Bank 1). The car also feels a bit rough at idle, and I think my fuel economy might have dropped slightly. It's not a dramatic difference, but enough to notice.

I've heard P0171 can be caused by a lot of things. What are the most common culprits for this code on a Dodge Journey? I'm hoping it's something I can check myself before having to take it to a shop. Any pointers on where to start looking for vacuum leaks or other issues would be great.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 4:14 AM

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ClearTheCode admin answer: The P0171 code, 'System Too Lean (Bank 1)', indicates that the engine's computer (PCM) is detecting too much oxygen in the exhaust, meaning the engine is running with an air-to-fuel ratio that is too lean. This can be caused by various factors, primarily unmetered air entering the system or insufficient fuel delivery. Here's a troubleshooting guide:

  1. Vacuum Leaks: This is one of the most common causes. Inspect all vacuum lines, intake manifold gaskets, PCV valve and hose, and brake booster hose for cracks, disconnections, or leaks. A good way to check for leaks is to listen for a hissing sound or use a smoke machine (professional tool) to pinpoint the exact location.
  2. Mass Air Flow (MAF) Sensor: A dirty or faulty MAF sensor can send incorrect air mass readings to the PCM, leading it to under-fuel the engine. Try cleaning the MAF sensor with specialized MAF sensor cleaner (never use other chemicals). If the problem persists, the sensor might need replacement.
  3. Oxygen (O2) Sensor: While less common for a P0171, a failing upstream O2 sensor can provide inaccurate readings, causing the PCM to incorrectly adjust fuel trims. However, a lean condition usually causes the O2 sensor to read correctly, so this is usually a symptom, not the cause.
  4. Fuel Delivery Issues:
    • Clogged Fuel Filter: A partially clogged fuel filter can restrict fuel flow.
    • Weak Fuel Pump: A failing fuel pump may not be able to deliver adequate fuel pressure, especially under load.
    • Dirty/Clogged Fuel Injectors: One or more clogged fuel injectors can reduce fuel delivery to the cylinders. Consider using a quality fuel system cleaner.
  5. Exhaust Leaks: An exhaust leak before the upstream O2 sensor can allow outside air in, tricking the sensor into thinking the engine is running lean.

When to See a Shop:

  • If you've checked for obvious vacuum leaks and cleaned the MAF sensor without success.
  • If you suspect fuel delivery issues (low fuel pressure) or a faulty O2 sensor, as these require specialized diagnostic tools.
  • If the issue persists, as prolonged lean conditions can lead to engine damage, including catalytic converter failure.
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