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P0300

Mercedes-Benz GLS GuideCritical Severity

P0300 on Mercedes-Benz GLS: Symptoms, Causes & DIY Fix

Official technical diagnostic wire for fault code P0300 (P0300: Random or Multiple Cylinder Misfire Detected) 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

$100 - $600 (DIY: $30 - $120)

GLS Direct Fit

Shop Labor Quote

$180 – $380

Based on $185/hr labor

Drivability Status

Not Drivable

Critical urgency level

Est. DIY Time

45 – 90 Min

Basic hand tools

Check P0300 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 P0300 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 P0300, drivers commonly observe:

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

Engine shaking, vibrating, or jerking at idle on Mercedes-Benz GLS (3.0L Turbo I6 (GLS 450) / 4.0L Bi-Turbo V8 (GLS 580 / Maybach))

Noticeable loss of engine power when accelerating on Mercedes-Benz GLS (3.0L Turbo I6 (GLS 450) / 4.0L Bi-Turbo V8 (GLS 580 / Maybach))

Strong gasoline smell from exhaust or poor fuel economy on Mercedes-Benz GLS (3.0L Turbo I6 (GLS 450) / 4.0L Bi-Turbo V8 (GLS 580 / Maybach))

Stumbling or stalling at stoplights 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%

Worn or fouled spark plugs and damaged spark plug wires (Mercedes-Benz OEM Part)

25%

Failing ignition coils or coil packs (Mercedes-Benz OEM Part)

12%

Clogged fuel injectors or low fuel rail pressure (Mercedes-Benz OEM Part)

Intake manifold vacuum leak (Mercedes-Benz OEM Part)

Low engine compression or faulty Camshaft/Crankshaft sensor (Mercedes-Benz OEM Part)

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

Scan with OBD-II Scanner for Accompanying Codes

Plug a handheld OBD-II scanner into the 16-pin port under the dashboard. Check if specific cylinder codes like P0301 (Cylinder 1) or P0304 (Cylinder 4) accompany P0300. 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 Code Reader / Scanner

Inspect and Replace Spark Plugs

Remove the ignition coils, use a spark plug socket with ratchet to unthread spark plugs. Inspect electrode tips for carbon buildup, oil fouling, or burnt gaps. Replace with OEM iridium plugs gapped to spec. on the Mercedes-Benz GLS equipped with 3.0L Turbo I6 (GLS 450) / 4.0L Bi-Turbo V8 (GLS 580 / Maybach).

Required Tool: 5/8 Spark Plug Socket, Ratchet Extension, Gap Gauge

Test Ignition Coils

Perform an ignition swap test: Swap coil from a suspected misfiring cylinder to an adjacent cylinder. Clear codes and re-scan. If the misfire moves, replace the faulty coil. on the Mercedes-Benz GLS equipped with 3.0L Turbo I6 (GLS 450) / 4.0L Bi-Turbo V8 (GLS 580 / Maybach).

Required Tool: 10mm Socket, Multimeter

Check for Vacuum Leaks

Inspect PCV hoses, intake boot, and vacuum lines for cracking or hissing sounds while engine idles. Smoke test the intake if necessary. on the Mercedes-Benz GLS equipped with 3.0L Turbo I6 (GLS 450) / 4.0L Bi-Turbo V8 (GLS 580 / Maybach).

Required Tool: Carb cleaner spray or Smoke machine

Verify Fuel Delivery and Clear DTC Codes

Add a bottle of premium fuel injector cleaner (e.g. Chevron Techron). Clear the OBD-II codes with your scanner and take the car on a 15-minute drive cycle to confirm readiness monitors reset. 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 P0300 FAQs

What causes code P0300 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)), P0300 is most frequently caused by Worn or fouled spark plugs and damaged spark plug wires or Failing ignition coils or coil packs. Factory sensor degradation or wiring harness wear near the engine bay are common factors.

Can I safely drive my Mercedes-Benz GLS with code P0300?

No. Driving with a flashing check engine light causes irreversible catalytic converter damage. Given that P0300 carries a Critical 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 P0300 on a Mercedes-Benz GLS?

DIY replacement parts typically range between $100 - $600 (DIY: $30 - $120). If serviced at an authorized Mercedes-Benz dealership, expect an additional $120–$250 in professional labor based on their $185/hr hourly rate.