OBD-II trouble code
P0057: HO2S Heater Control Circuit Low (Bank 2, Sensor 2)
A post-catalyst oxygen sensor heater on the second cylinder bank drew less current than commanded. Only V-configuration and flat engines can set this code, and the sensor involved is usually the hardest one on the vehicle to reach.
Quick facts
- System
- Powertrain
- Category
- Oxygen Sensor
- Severity
- Low severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $10 – $550
- DIY difficulty
- Intermediate DIY
What does P0057 mean?
Before you diagnose anything, this code tells you something about your engine: it has two cylinder heads. Bank 2 is defined as the bank that does not contain cylinder number 1, so it exists only on V6, V8, V10 and flat engine layouts. An inline four or inline six has no bank 2 and cannot legitimately store P0057. When a scan tool reports it on an inline engine, the usual explanation is that the tool is set to the wrong vehicle rather than a real fault.
The code itself concerns the heater built into the oxygen sensor mounted after that bank's catalytic converter. The engine control module energizes the heater and monitors the circuit; when current comes in below the expected level, it stores P0057. Low current means resistance where there should be almost none — a burned-out element, a corroded terminal, a broken conductor, or a lost feed.
The practical reason P0057 deserves separate treatment from its bank 1 twin is access. On the transverse V6 layout used by a large share of front-wheel-drive sedans, minivans and crossovers, one bank faces the radiator and the other is jammed against the firewall, and its exhaust plumbing has to wrap around or over the transmission before it reaches the underbody. Whichever bank ends up in that position carries the longest and most awkward oxygen sensor harness on the vehicle, often with an extra intermediate connector to allow the engine to rock on its mounts. More connectors and more length mean more places to fail, and the labor to reach any of them is higher than the equivalent work on the accessible bank.
There is also a design point worth checking before you go looking. Not every V engine has two post-catalyst sensors. Plenty of them merge both banks into a Y-pipe ahead of a single underfloor converter with one downstream sensor, and those vehicles do not have a bank 2 sensor 2 at all. If you cannot find a second post-catalyst sensor after locating the first, verify the exhaust layout for your specific application rather than assuming one is hidden.
Companion codes are unusually informative here. P0057 stored beside P0051, the upstream heater code for the same bank, suggests a shared connector, ground or harness section serving that side of the engine. P0057 stored beside P0037 — the same fault on the other bank — points instead at a shared fuse or a common ground, and one repair should clear both.
Common causes
- Open heater element inside the bank 2 post-catalyst oxygen sensor
- Corroded or water-intruded intermediate connector on the long bank 2 harness run
- Broken conductor where the harness flexes as the engine rocks on its mounts
- Blown oxygen sensor heater fuse shared with other heater circuits
- Heat damage to the pigtail where it passes close to the rear bank exhaust manifold or heat shield
- Poor ground on the bank 2 heater return path
- Universal replacement sensor spliced in with heater resistance outside the expected window
- Failed engine control module heater driver, which is uncommon
Symptoms
- Check engine light on with P0057 stored
- Catalyst efficiency monitor for bank 2 will not complete
- Emissions inspection failure with readiness not set
- No perceptible change in idle, power or driveability
- P0051 stored alongside, suggesting a shared bank 2 harness or connector fault
- P0037 stored alongside, suggesting a shared fuse or ground rather than two failed sensors
- Intermittent code that appears after driving on rough roads, where harness flex is involved
Diagnostic steps
- 1.Confirm the engine actually has two banks and two post-catalyst sensors. If both banks merge into a single underfloor converter with one downstream sensor, the sensor this code names does not exist and the fault is elsewhere.
- 2.Identify bank 2 properly — the bank without cylinder number 1 — using service data for your specific engine. On transverse V6 installations this is not predictable from where you are standing.
- 3.Note what else is stored. P0051 with P0057 points at that bank's shared harness; P0037 with P0057 points at a shared fuse or ground serving both banks.
- 4.Check the oxygen sensor heater fuse before disassembling anything on the harder bank. It costs nothing and saves an afternoon.
- 5.Unplug the sensor and measure across the two heater pins. Roughly 2 to 20 ohms is typical; an open reading confirms a failed element.
- 6.Inspect the intermediate connector in the bank 2 run specifically, and flex the harness where it bridges from the engine to the body while watching for the fault. Motion-related failures are more common on this side because the run is longer.
Repair cost
$10 – $550
A blown heater fuse is a few dollars. Connector and harness repair typically runs $80-$280, higher than the equivalent bank 1 job because the run is longer and access is worse. Sensor replacement generally lands at $180-$450, and on a transverse V6 where the sensor sits behind the engine against the firewall, some shops charge toward $550 because reaching it can mean removing heat shielding or dropping part of the exhaust.
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.
Related repairs
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.