Is P0057 a serious problem?

It's one of the milder oxygen-sensor codes. The downstream sensor is used mainly to watch the catalytic converter, not to control fueling, so the engine runs normally. The real consequences are an incomplete catalyst-efficiency monitor and a failed emissions test, so plan to fix it before your next inspection.

What's the difference between P0057 and P0037?

They're the same downstream heater-circuit-low fault on opposite banks. P0037 is Bank 1, Sensor 2, and P0057 is Bank 2, Sensor 2 — the side that does not contain cylinder number 1. Only two-bank engines such as V6s and V8s can set P0057. The diagnosis is identical; you just work on the Bank 2 downstream sensor.

Can I just replace the heater on the downstream sensor?

No. Like all modern oxygen sensors, the heater is built into the sensor housing and isn't a separate part. A failed heater element means replacing the complete downstream sensor. Only wiring, connector, or fuse problems can be repaired without a new sensor.

Will P0057 hurt my fuel economy?

Usually not in any noticeable way. The downstream sensor doesn't drive fuel trim, so a heater fault there has little effect on how the engine runs or how much fuel it uses. The main downside is emissions monitoring and a failed inspection, not driveability.

OBD-II trouble code

P0057: HO2S Heater Control Circuit Low (Bank 2, Sensor 2)

The engine computer commanded the heater in the Bank 2 downstream oxygen sensor to turn on, but measured too little voltage or current on the control circuit. Usually a failed heater or wiring fault. The car runs normally, but it will fail an emissions test.

Quick facts

System: Powertrain
Category: Oxygen Sensor
Severity: Low severity
Drivable: Usually safe to drive short-term
Repair cost range: $0 – $400
DIY difficulty: Intermediate DIY

What does P0057 mean?

Sensor 2 on Bank 2 is the downstream oxygen sensor, mounted after the catalytic converter on the side of the engine that does NOT contain cylinder number 1. Its main job is to monitor catalyst efficiency by comparing the exhaust oxygen content before and after the converter. Like the upstream sensor, it has a built-in electric heater that brings it up to operating temperature quickly so it can start reporting accurate readings soon after a cold start.

The engine control module (ECM) switches that heater circuit and watches the voltage and current. P0057 sets when the ECM commands the downstream heater on but reads a LOW value on the control circuit — too little current flow, which typically indicates high resistance, an open, or a short to ground in the heater circuit. It is the Bank 2 counterpart to P0037 (Bank 1, Sensor 2) and the downstream equivalent of P0051, which covers the upstream sensor on the same bank.

Because the downstream sensor is used mainly for catalyst monitoring rather than active fuel control, P0057 has a lower severity than the upstream heater codes — the engine's fuel management doesn't depend on it. The practical consequences are that the catalyst-efficiency monitor may not run and the vehicle will fail an OBD-II emissions inspection. As with all modern oxygen sensors, the heater is built into the sensor, so a genuinely failed heater element means replacing the sensor, but wiring, connector, and fuse faults should be ruled out first.

Common causes

Failed heater element inside the Bank 2 downstream oxygen sensor (most common — the sensor needs replacement)
Corroded, loose, or damaged sensor connector
Chafed, open, or shorted heater-circuit wiring, often near the hot exhaust or along the underbody
Blown oxygen-sensor heater fuse (can affect multiple sensors at once)
Poor ground on the heater circuit
Failed heater driver inside the ECM (rare)

Symptoms

Check engine light is on
Catalyst-efficiency monitor may not complete (readiness not set)
Failed emissions inspection
Rarely any noticeable driveability symptoms
Companion codes such as P0051, P0058, or P0161 on some vehicles

Diagnostic steps

1.Scan for all stored codes. Several heater codes together suggest a shared fuse, ground, or power feed rather than one sensor.
2.Inspect the Bank 2 downstream sensor connector and the harness routing along the underbody and near the exhaust for chafing or corrosion.
3.Check the oxygen-sensor heater fuse; a blown fuse is cheap and often explains companion heater codes.
4.With the sensor unplugged, measure heater resistance across the two heater pins. Roughly 2 to 20 ohms is typical depending on manufacturer; an open (infinite) reading confirms an internal heater failure.
5.Confirm the heater circuit has power and a good ground with the key on. Missing power or ground points to wiring or fuse issues.
6.If the heater resistance is out of spec and the wiring, ground, and fuse check out, replace the Bank 2 downstream oxygen sensor.

Repair cost

$0 – $400

A blown fuse is a few dollars. Wiring or connector repair typically runs $50 to $200. Replacing the downstream oxygen sensor is usually $150 to $400 parts and labor, though a rusted-in sensor on an older vehicle can add labor. The heater is integrated into the sensor, so a failed heater element means full sensor replacement.

Estimate your repair

Run the numbers for your vehicle

Open the Repair Cost Estimator with oxygen sensor replacement preselected. Adjust labor rate and vehicle category to fit your situation.

Estimate your repair cost

DIY vs shop

This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.

Related codes

P0037 P0038 P0051 P0058 P0161