P01610 O2 sensor heater circuit bank 2 sensor 2 malfunction

What the code means

Bank 2 Sensor 2 (B2S2)

Bank 2 = the side of the engine without cylinder #1

Sensor 2 = downstream oxygen sensor (after the catalytic converter)

Heater circuit malfunction = the built-in heater inside the O2 sensor is not working properly or not getting power/ground

The heater helps the sensor reach operating temperature quickly.

Common OBD-II codes related

P0161 – O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 2)

Sometimes also: P0056, P0141, depending on manufacturer

Most common causes (in order)

1. Failed O2 sensor heater (very common)

2. Blown fuse for O2 heater circuit

3. Broken or burned wiring (especially near exhaust)

4. Poor ground connection

5. PCM issue (rare)

Step-by-step diagnostic process (recommended)

1 Visual inspection (always first)

Check wiring near exhaust for:

Melted insulation

Broken wires

Corrosion in connector

Check connector pins for looseness or green corrosion

👉 Many fixes stop here.

2 Check the fuse

Locate O2 heater fuse (label may say):

O2 HTR

A/F HTR

ENG SENSOR

Use a multimeter or test light

Replace if blown

⚠️ If the fuse blows again → wiring short or bad sensor

3 Test the heater resistance (key OFF)

Unplug the O2 sensor connector.

Set multimeter to ohms (Ω)

Measure across the heater pins (usually same color wires)

Normal range:
➡️ 3–15 ohms (check vehicle spec)

❌ OL / Infinite resistance = heater is burned out → replace sensor
❌ 0 ohms = internal short → replace sensor

4 Check power supply (key ON)

One heater wire should have battery voltage (12V)

If no power:

Trace wiring back to fuse/relay

Check PCM command (some vehicles switch ground, not power)

5 Check ground control

PCM usually controls ground side

Use a test light from battery + to heater ground wire

Light should pulse or stay on when engine is running

No ground → wiring or PCM issue (rare)

Repair recommendation (for customers)

If resistance is bad → replace O2 sensor

Always recommend OEM or high-quality brand (Denso, NTK, Bosch)

Clear code and perform a drive cycle

Important notes for your business

Downstream O2 sensors do NOT affect fuel trim, but:

They will fail emissions

MIL light stays on

Do not replace catalytic converter for this code alone.

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