DTC P0167 and how to diagnose it efficiently for a car service business.

🔧 Code: P0167

O2 Sensor Heater Circuit Malfunction

Bank 2 – Sensor 3

📍 What this sensor is

Bank 2 → The side of the engine without cylinder #1

Sensor 3 → Downstream oxygen sensor (usually after the catalytic converter)

This sensor has a built-in heater so it reaches operating temperature quickly.

P0167 means the ECM sees an electrical problem in the heater circuit, not the oxygen reading itself.

⚠️ Common Causes (Most to Least Likely)

1. Failed O2 sensor heater (very common)

2. Open or shorted wiring near exhaust (heat damage)

3. Blown heater fuse

4. Poor ground connection

5. ECM driver failure (rare)

🛠️ Diagnostic Steps (Professional Workflow)

1 Visual Inspection (Don’t skip)

Check sensor wiring for:

Melted insulation

Broken or stretched wires

Oil or water intrusion

Inspect connector pins for corrosion or looseness

👉 Many P0167 issues are found here.

2 Check Heater Resistance (Key OFF)

Unplug the O2 sensor

Measure resistance across heater pins (usually same-color wires)

Typical spec:

✅ 3–15 ohms (check service info for vehicle)

∞ (open circuit) → Heater is bad → Replace sensor

0 ohms / very low → Shorted heater → Replace sensor

3 Verify Power Supply (Key ON)

Back-probe heater power wire

You should see battery voltage (12V)

❌ No voltage:

Check O2 heater fuse

Check relay (if equipped)

Trace wiring back to power source

4 Check Ground Control

ECM usually controls the ground side

With engine running, check for ground pulsing

No ground signal → possible wiring issue or ECM fault (rare)

🔁 Repair Solutions

✅ Replace Bank 2 Sensor 3 (OEM or high-quality aftermarket)

✅ Repair damaged wiring

✅ Replace blown fuse (always find root cause)

❌ Avoid universal sensors unless properly spliced

🚗 After Repair

Clear codes

Road test

Ensure sensor goes into closed loop

Verify heater status on scan tool (if available)

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