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P0171

Mercedes-Benz GLS GuideMedium Severity

P0171 on Mercedes-Benz GLS: Symptoms, Causes & DIY Fix

Official technical diagnostic wire for fault code P0171 (P0171: System Too Lean (Bank 1)) specifically affecting Mercedes-Benz GLS vehicles equipped with 3.0L Turbo I6 (GLS 450) / 4.0L Bi-Turbo V8 (GLS 580 / Maybach).

DIY Parts Estimate

$80 - $350 (DIY: $15 - $70)

GLS Direct Fit

Shop Labor Quote

$180 – $380

Based on $185/hr labor

Drivability Status

Drivable (Short Trip)

Medium urgency level

Est. DIY Time

45 – 90 Min

Basic hand tools

Check P0171 On Another Mercedes-Benz Model:

Mercedes-Benz C-Class Mercedes-Benz E-Class Mercedes-Benz S-Class Mercedes-Benz GLC Mercedes-Benz GLE Mercedes-Benz GLS Mercedes-Benz G-Class

1. Symptoms of P0171 on Mercedes-Benz GLS

When the Engine Control Module (ECM/PCM) on your Mercedes-Benz GLS (3.0L Turbo I6 (GLS 450) / 4.0L Bi-Turbo V8 (GLS 580 / Maybach)) logs fault code P0171, drivers commonly observe:

Check Engine Light on on Mercedes-Benz GLS (3.0L Turbo I6 (GLS 450) / 4.0L Bi-Turbo V8 (GLS 580 / Maybach))

Rough idling or engine hesitation on acceleration on Mercedes-Benz GLS (3.0L Turbo I6 (GLS 450) / 4.0L Bi-Turbo V8 (GLS 580 / Maybach))

Hard starting in cold weather on Mercedes-Benz GLS (3.0L Turbo I6 (GLS 450) / 4.0L Bi-Turbo V8 (GLS 580 / Maybach))

Pinging or knocking sound under load on Mercedes-Benz GLS (3.0L Turbo I6 (GLS 450) / 4.0L Bi-Turbo V8 (GLS 580 / Maybach))

Mercedes-Benz GLS OBD-II Port Location

The 16-pin diagnostic connector is located Driver lower knee bolster trim panel. Plug in your scan tool to verify freeze-frame sensor values.

2. Most Likely Causes on Mercedes-Benz GLS

Historical warranty claims and technical repair bulletins for Mercedes-Benz GLS point to the following failure distribution:

55%

Dirty or failing Mass Air Flow (MAF) sensor (Mercedes-Benz OEM Part)

25%

Cracked intake air boot or disconnected vacuum hose (Mercedes-Benz OEM Part)

12%

Clogged fuel filter or weak fuel pump (Mercedes-Benz OEM Part)

Stuck open PCV valve or leaking intake manifold gasket (Mercedes-Benz OEM Part)

3. Step-by-Step DIY Repair Guide for Mercedes-Benz GLS

Clean the Mass Airflow (MAF) Sensor

Disconnect the battery, unclip the MAF sensor on the air intake tube, and spray 10-15 bursts of dedicated MAF cleaner onto the thin wire sensor. Allow to dry 15 minutes before reinstalling. on the Mercedes-Benz GLS equipped with 3.0L Turbo I6 (GLS 450) / 4.0L Bi-Turbo V8 (GLS 580 / Maybach).

Required Tool: CRC MAF Sensor Cleaner, Screwdriver

Inspect Intake Air Ducting

Check the rubber accordion hose between air filter box and throttle body for tears or dry rot cracks. on the Mercedes-Benz GLS equipped with 3.0L Turbo I6 (GLS 450) / 4.0L Bi-Turbo V8 (GLS 580 / Maybach).

Required Tool: Flashlight

Inspect PCV Valve and Hoses

Shake the PCV valve; if it doesn't rattle cleanly, replace it. Inspect attached rubber hoses for collapsing. on the Mercedes-Benz GLS equipped with 3.0L Turbo I6 (GLS 450) / 4.0L Bi-Turbo V8 (GLS 580 / Maybach).

Required Tool: Pliers

Check Fuel Pressure

Connect fuel pressure gauge to the Schrader valve on fuel rail. Verify pressure meets factory PSI specs. on the Mercedes-Benz GLS equipped with 3.0L Turbo I6 (GLS 450) / 4.0L Bi-Turbo V8 (GLS 580 / Maybach).

Required Tool: Fuel Pressure Tester Kit

Clear Codes and Reset Fuel Trims

Clear DTCs and verify Long Term Fuel Trims (LTFT) return below +/- 10% on your scanner. on the Mercedes-Benz GLS equipped with 3.0L Turbo I6 (GLS 450) / 4.0L Bi-Turbo V8 (GLS 580 / Maybach).

Required Tool: OBD-II Scanner

4. Mercedes-Benz GLS P0171 FAQs

What causes code P0171 to trigger on a Mercedes-Benz GLS?

On the Mercedes-Benz GLS (3.0L Turbo I6 (GLS 450) / 4.0L Bi-Turbo V8 (GLS 580 / Maybach)), P0171 is most frequently caused by Dirty or failing Mass Air Flow (MAF) sensor or Cracked intake air boot or disconnected vacuum hose. Factory sensor degradation or wiring harness wear near the engine bay are common factors.

Can I safely drive my Mercedes-Benz GLS with code P0171?

Yes, but prolonged lean running increases cylinder combustion temperatures. Given that P0171 carries a Medium severity rating on Mercedes-Benz vehicles, we advise performing diagnostic scanning via the OBD-II port located driver lower knee bolster trim panel before extended highway driving.

Where is the diagnostic port located on the Mercedes-Benz GLS?

The 16-pin OBD-II DLC connector on the Mercedes-Benz GLS is situated driver lower knee bolster trim panel. It requires no special tools to plug in a standard scanner.

How much does it cost to fix P0171 on a Mercedes-Benz GLS?

DIY replacement parts typically range between $80 - $350 (DIY: $15 - $70). If serviced at an authorized Mercedes-Benz dealership, expect an additional $120–$250 in professional labor based on their $185/hr hourly rate.