What causes fault code P050D?

• Most likely: Clogged or leaking fuel injectors • Likely: Failing spark plugs or ignition coils • Possible: Faulty Engine Coolant Temperature (ECT) sensor providing incorrect cold-start data • Possible: Vacuum leak or PCV system issues • Rare: Poor fuel quality or contaminated fuel • Rare: Internal engine mechanical issues (e.g., carbon buildup on intake valves)

How do you fix fault code P050D?

STEP 1: Inspect fuel injectors for leaks. A leaking injector drips fuel into the cylinder overnight, causing a flooded condition and rough idle upon startup. STEP 2: Perform a fuel pressure leak-down test. Pressure should remain stable after pump shut-off (typically 45-60 PSI). A rapid drop indicates a leaking injector or fuel pressure regulator. STEP 3: Check ignition components. Inspect spark plugs for fouling. Test ignition coils using an oscilloscope or scan tool for misfire counts. STEP 4: Clean intake valves (especially on GDI engines) for carbon buildup. Verify ECT sensor accuracy by comparing sensor data to ambient temperature before cold start.

Powertrain (Engine & Gearbox)Standard EOBD

P050D - Cold Start Rough Idle

Q: What are the symptoms of fault code P050D?

• Check engine light (MIL) illuminated • Rough or erratic idle during the first 30-60 seconds after startup • Engine may stall immediately after cold start • Hesitation or stumble during warmup acceleration • Strong fuel smell from the exhaust during cold starts

Last updated:1 February 2026

Related:Fuel Injector, Spark Plug, Crankshaft Position Sensor (CKP), Ignition Coils, Motortemperaturgivare (ECT)

System

Powertrain (Engine & Gearbox)

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Vehicle Speed Sensor 'A' Range/Performance

P0502

Vehicle Speed Sensor 'A' Circuit Low Input

P0503

Vehicle Speed Sensor (VSS) Intermittent/Erratic/High

Technical Description

P050D is stored when the Engine Control Module (ECM) detects a rough idle condition during a cold start, specifically before the engine reaches normal operating temperature. The ECM monitors the crankshaft position sensor for minute fluctuations in RPM that indicate poor combustion quality. Unlike general misfire codes (P0300-P0308), P050D is specifically triggered during the catalyst warm-up phase, where ignition timing and fuel delivery are manipulated to reduce emissions during the startup cycle.

Possible Causes

Clogged or leaking fuel injectors

Failing spark plugs or ignition coils

Faulty Engine Coolant Temperature (ECT) sensor providing incorrect cold-start data

Vacuum leak or PCV system issues

Poor fuel quality or contaminated fuel

Internal engine mechanical issues (e.g., carbon buildup on intake valves)

Symptoms

Check engine light (MIL) illuminated

Rough or erratic idle during the first 30-60 seconds after startup

Engine may stall immediately after cold start

Hesitation or stumble during warmup acceleration

Strong fuel smell from the exhaust during cold starts

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P050D - Cold Start Rough Idle

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P050D - Cold Start Rough Idle

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Symptoms

Recommended Solution

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Mechanic's Tip

Do you also have other fault codes?

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