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2018 Velar P0171/P0174 - Lean Codes and Rough Idle

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Robert C. · rep 0 · May 22, 6:26 AM · 1 replies · solved · Question

Vehicle: 2018 Land Rover Range Rover Velar P380 R-Dynamic HSE

Hey everyone,

I'm having some trouble with my 2018 Range Rover Velar P380 R-Dynamic HSE. A few days ago, the check engine light came on, and I've noticed a rough idle, especially when the engine is cold. It feels a bit sluggish sometimes too.

I hooked up my OBD-II scanner, and it's throwing codes P0171 (System Too Lean, Bank 1) and P0174 (System Too Lean, Bank 2). Both banks are showing lean, which makes me think it's something affecting the whole engine rather than just one side.

Has anyone else experienced these codes on their Velar or similar Land Rover models from this generation? What are the most common culprits I should be looking at first? I'm hoping to tackle some of the simpler checks myself before taking it to the dealership.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 6:26 AM

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ClearTheCode admin answer:

Codes P0171 and P0174 indicate that your engine's computer (ECM) is detecting a lean condition, meaning there's too much air or not enough fuel in the combustion mixture for both banks of the engine. This is a common issue with several potential causes, especially on a 2018 Range Rover Velar.

Here are the most common causes and diagnostic steps:

  1. Vacuum Leaks: This is often the primary suspect when both banks are lean. A leak in the intake system allows unmetered air into the engine. Common areas include:

    • Intake manifold gaskets
    • PCV (Positive Crankcase Ventilation) system hoses or valve
    • Brake booster hose
    • Any other vacuum lines connected to the intake manifold.
    • Diagnostic Step: A smoke test is the most effective way to find vacuum leaks. You can also listen for a hissing sound around the engine bay.

  2. Mass Air Flow (MAF) Sensor: A dirty or faulty MAF sensor can report incorrect air intake readings to the ECM, leading it to reduce fuel delivery, causing a lean condition. If the sensor is under-reporting airflow, the ECM will inject less fuel than needed.

    • Diagnostic Step: Inspect and clean the MAF sensor with specialized MAF cleaner. Check live data for MAF readings at idle and under load.

  3. Fuel Delivery Issues: If the engine isn't getting enough fuel, it will run lean. This could be due to:

    • Weak Fuel Pump: Not providing adequate fuel pressure.
    • Clogged Fuel Filter: Restricting fuel flow.
    • Clogged Fuel Injectors: Not spraying enough fuel, or spraying an incorrect pattern.
    • Diagnostic Step: Perform a fuel pressure test at the fuel rail. Check fuel trim data with a scanner; high positive long-term fuel trims indicate the ECM is trying to add fuel but can't compensate enough.

  4. Exhaust Leaks (Pre-O2 Sensor): An exhaust leak before the upstream oxygen sensors can cause them to read excess oxygen, tricking the ECM into thinking the engine is running rich and reducing fuel, leading to an actual lean condition.

    • Diagnostic Step: Visually inspect the exhaust manifold and exhaust pipes before the catalytic converters for any signs of leaks.

When to See a Shop: If you've checked for obvious vacuum leaks, cleaned your MAF sensor, and the codes persist, it's time to consult a qualified Land Rover specialist. They have advanced diagnostic tools (like smoke machines for precise leak detection and professional scan tools for in-depth live data analysis) and the expertise to accurately diagnose and repair complex fuel system or sensor issues specific to your Velar. Continued driving with a lean condition can lead to engine damage, including catalytic converter failure.

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