DTC P0057 – O2 Sensor Heater Control Circuit Low (Bank 2 Sensor 2).

🔧 P0057 – O2 Sensor Heater Control Circuit Low
Sensor: Bank 2 Sensor 2 (Downstream O₂ sensor, after catalytic converter on Bank 2)
Meaning:
The ECM detects low voltage in the heater circuit of the O₂ sensor → heater not working properly → slower warm-up → delayed closed-loop operation.

✅ Common Causes

Electrical

🔌 Open heater circuit in the sensor

🔧 Faulty O₂ sensor heater element (internal open)

🔥 Blown O₂ sensor heater fuse

📉 High resistance in wiring or connectors

🟫 Corroded connectors at sensor or ECM

⚡ Poor ground for heater circuit

Vehicle-Side

🧯 Exhaust heat damage to wiring

🪫 Low battery voltage / charging issues (less common)

🧰 How to Diagnose (Step-by-Step)

1. Identify Bank 2 Sensor 2 Location

Bank 2 = the cylinder head not containing cylinder #1
Sensor 2 = downstream, after catalytic converter.

2. Check Fuses

Look for fuses labelled:

O₂ Sensor Heater

EFI

ENG1 / ENG2

A/F heater

➡️ If blown, check wiring for short before replacing.

3. Inspect Wiring & Connector

Melted or brittle wires near exhaust

Water/oil contamination

Loose or damaged pins

Repair any damage and clear code.

4. Measure Heater Resistance (Sensor Side)

Unplug O₂ sensor → identify heater pins (usually same-color wires).

Using a multimeter:

Typical heater resistance: 3–14 Ω depending on vehicle

Infinite (OL) = heater open → replace sensor

Very high resistance (>20 Ω) → sensor faulty

5. Check Power Supply (Vehicle Side)

Turn ignition ON (engine OFF)

One heater wire should have battery voltage (12V)

Other wire is ECM-controlled ground

If no power, trace back to fuse or wiring.

6. Check ECM Ground Control

Using a test light:

Connect test light to battery positive

Probe the ECM-controlled wire

Crank engine → ECM should pulse ground

If ECM does not ground:

Wiring fault between sensor → ECM

Rarely, ECM driver failure

🔧 Common Fixes

🌟 Replace O₂ sensor (most common fix)
🌟 Repair/replace burnt wiring
🌟 Clean or repin connector
🌟 Replace blown fuse
🌟 Fix poor ground connection
🌟 Repair wiring from ECM if open🚗

When the Code Returns Immediately

If P0057 comes back instantly after clearing:

Sensor heater is open-circuit

1. Power supply missing‍

Ground wire broken

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