DTC P0050 – O₂ Sensor Heater Control Circuit (Bank 2 Sensor 1).

✅ DTC P0050 – Meaning

P0050 indicates a problem in the oxygen sensor heater circuit of Bank 2 Sensor 1 (upstream sensor, before catalytic converter, on the side of engine with cylinder #2).

The heater inside the O₂ sensor helps it reach operating temperature quickly. If the heater circuit has open, short, or power/ground issue, the ECU sets P0050.

🔧 Common Causes

Electrical

🔌 Blown fuse for O₂ heater (very common)

⚡ Open circuit in heater wiring

⚠️ Short to ground / short to power

🛠 Corroded or loose O₂ sensor connector

🔋 Low battery voltage or charging system issue

Component

❌ Failed O₂ sensor heater element

❌ Damaged wiring harness (heat, road debris, exhaust heat)

ECU-related

Rare: ECM driver failure

🔍 Step-by-Step Diagnosis (Fast & Accurate)

✅ 1. Check O₂ Heater Fuse

Most cars have a fuse labeled:

O₂ HTR

A/F Heater

EFI

ENG1 / ENG2

👉 If fuse is blown:

Replace fuse.

Check wiring for short.

If fuse blows again → sensor heater may be shorted.

✅ 2. Inspect Wiring & Connector at Bank 2 Sensor 1

Look for:

Melted wiring near exhaust

Broken insulation

Corrosion inside connector

Loose pins

Repair any damage.

✅ 3. Check Heater Resistance of Sensor

Unplug sensor and measure heater resistance between heater pins.

Typical heater specs:

3–20 ohms (varies by manufacturer)

📌 If OL (open) or infinite → heater open → replace O₂ sensor
📌 If 0–1 ohm → internal short → replace sensor

✅ 4. Check Power Supply to Heater

Turn ignition ON (engine not running).

One heater wire should have:

Battery voltage (12V)

If no voltage:

Check fuse again

Check relay (if present)

Trace wiring back to ECM

✅ 5. Check Ground Side Controlled by ECU

The ECM usually controls the ground side of the heater.

Test:

Connect a test light to battery positive and probe heater ground wire.

Crank engine → test light should blink or stay on.

🎯 If no ground control → possible ECM driver failure.

🔧 Fixes Based on What You Find

Finding Fix

Blown fuse Replace fuse + inspect wiring for short
No power to heater Repair power circuit / fuse / relay
Open heater resistance Replace O₂ sensor
Shorted heater (low resistance) Replace O₂ sensor
Damaged wiring Repair harness
ECM not controlling ground Check wiring → ECM issue

🧰 Recommended Repair

In most cases (70–80%), P0050 is fixed by: 👉 Replacing Bank 2 Sensor 1 O₂ sensor
after confirming the heater is open.

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