If your OBD-II scanner displays P0057, your vehicle’s Engine Control Module (ECM) or Powertrain Control Module (PCM) has detected a low-voltage condition in the heated oxygen sensor (HO2S) heater control circuit for Bank 2 Sensor 2.
The generic SAE definition for P0057 is:
HO2S Heater Control Circuit Low Bank 2 Sensor 2
This code indicates the ECM has detected lower-than-expected voltage or higher-than-expected current in the heater circuit of the downstream oxygen sensor located on Bank 2.
Depending on the manufacturer, Bank 2 Sensor 2 may also be referred to as:
- Heated Oxygen Sensor (HO2S)
- Rear Oxygen Sensor
- Downstream Oxygen Sensor
- Post-Catalytic Converter Oxygen Sensor
- Lambda Sensor
- Catalyst Monitoring Sensor
- Rear Air/Fuel Ratio Sensor
Unlike P0056, which identifies a general heater circuit fault, P0057 specifically indicates the heater circuit voltage is lower than expected, typically because the circuit is shorted or the heater element has failed internally.
Common causes include:
- Shorted heater element
- Short to ground
- Melted wiring
- Damaged oxygen sensor
- Corroded connector
- Water intrusion
- Incorrect replacement sensor
- Harness damage
- ECM driver failure (rare)
Although P0057 rarely causes drivability concerns, it can increase emissions, delay catalyst monitoring, and prevent emissions readiness monitors from completing.
For additional diagnostic information, visit:
- Complete OBD-II Code Library: https://my.prostreetonline.com/dtc-obdii/
- Body B-Code Library: https://my.prostreetonline.com/dtc-doctor/b-code-obd-ii-codes/
- Chassis C-Code Library: https://my.prostreetonline.com/dtc-doctor/c-code-obd-ii-codes/
P0057 Quick Facts
| Item | Information |
|---|---|
| OBD-II Code | P0057 |
| Description | HO2S Heater Control Circuit Low Bank 2 Sensor 2 |
| Category | Powertrain |
| System | Emissions |
| Sensor | Bank 2 Sensor 2 |
| Sensor Location | Downstream (After Catalytic Converter) |
| Severity | Low to Moderate |
| Safe to Drive? | Usually |
| Typical Repair Cost | $75–600 |
What Does P0057 Mean?
P0057 indicates the ECM has detected lower-than-normal voltage in the heater control circuit for the Bank 2 Sensor 2 oxygen sensor.
Most oxygen sensor heater circuits receive battery voltage while the ECM controls the ground side.
If the circuit becomes shorted or current increases beyond the calibrated limit, the ECM sees the voltage drop below its expected value and stores P0057.
This code often points toward:
- Internal heater short
- Wiring shorted to ground
- Melted insulation
- Damaged connector
- Water-contaminated wiring
What Is Bank 2 Sensor 2?
Bank 2 is the side of the engine that does not contain cylinder number one.
Sensor 2 is the oxygen sensor located after the catalytic converter.
Its primary responsibilities include:
- Monitoring catalytic converter efficiency
- Measuring post-catalyst oxygen levels
- Verifying emissions system performance
- Completing OBD-II readiness monitors
- Detecting catalyst deterioration
Unlike upstream oxygen sensors, the downstream sensor has very little effect on fuel delivery.
Why Does the Downstream Oxygen Sensor Have a Heater?
The downstream oxygen sensor must reach operating temperature quickly after startup.
The built-in heater allows the ECM to:
- Begin catalyst monitoring sooner
- Reduce cold-start emissions
- Complete readiness monitors faster
- Improve diagnostic accuracy
- Detect catalyst problems earlier
Without a functioning heater, the ECM must wait for exhaust heat to warm the sensor.
How the Heater Circuit Works
A typical heater circuit includes:
- Battery voltage
- Heater fuse
- Heater relay (on many vehicles)
- Internal heater element
- ECM-controlled ground
- Wiring harness
- Electrical connectors
The ECM monitors:
- Voltage
- Current draw
- Circuit continuity
- Warm-up rate
If current becomes excessive and voltage drops below expected values, P0057 is stored.
What Does “Circuit Low” Mean?
“Circuit Low” means the ECM detects lower-than-expected voltage in the heater circuit.
Common causes include:
- Shorted heater element
- Short to ground
- Melted wiring
- Water intrusion
- Damaged connector
- Pinched harness
- Internal oxygen sensor failure
Unlike P0058, this code generally indicates too much current flow, not too little.
How the ECM Detects P0057
The ECM performs heater diagnostics during cold starts.
It compares:
- Commanded heater operation
- Actual voltage
- Current flow
- Heater response
- Warm-up time
The ECM stores P0057 when it detects:
- Excessive current draw
- Low circuit voltage
- Shorted heater
- Grounded control circuit
- Electrical values outside calibrated specifications
Depending on manufacturer strategy, the MIL may illuminate immediately or after several drive cycles.
P0056 vs P0057 vs P0058
| Code | Description |
| P0056 | Heater Control Circuit |
| P0057 | Heater Control Circuit Low |
| P0058 | Heater Control Circuit High |
Generally:
- P0056 = General circuit fault
- P0057 = Low voltage / excessive current
- P0058 = High voltage / insufficient current
Symptoms of P0057
Common symptoms include:
- Check Engine Light
- Failed emissions inspection
- Catalyst monitor incomplete
- Increased cold-start emissions
- Delayed readiness monitors
Most drivers experience little or no change in drivability.
Common Causes of P0057
1. Shorted Heater Element
The heater inside the oxygen sensor develops an internal short.
This is one of the most common causes.
2. Wiring Shorted to Ground
The heater wiring may contact:
- Exhaust pipes
- Heat shields
- Engine block
- Transmission
- Chassis
Heat damage frequently causes insulation failure.
3. Melted Wiring Harness
Because downstream sensors operate near extremely hot catalytic converters, melted wiring is common.
4. Water Intrusion
Moisture entering the connector can create conductive paths that lower circuit voltage.
5. Damaged Connector
Inspect for:
- Bent pins
- Corrosion
- Loose terminals
- Broken locking tabs
- Water contamination
6. Incorrect Oxygen Sensor
Universal oxygen sensors sometimes have heater characteristics outside OEM specifications.
Use OEM-quality direct-fit sensors whenever possible.
7. Harness Damage
Look for:
- Pinched wiring
- Abrasion
- Rodent damage
- Previous repair splices
8. ECM Driver Failure
Rare.
Only suspect after all external testing confirms the sensor and wiring are functioning correctly.
Is P0057 Serious?
P0057 is generally considered low to moderate severity.
The vehicle usually remains drivable.
However, delaying repairs may result in:
- Increased emissions
- Failed emissions testing
- Incomplete catalyst monitors
- Additional oxygen sensor codes
- Possible wiring damage if a short is present
Can You Drive With P0057?
Yes, in most cases.
However, if the short is caused by melted wiring contacting the exhaust, repairs should be made immediately to prevent additional electrical damage.
How to Diagnose P0057
Step 1: Scan for Additional Codes
Check for:
- P0056
- P0058
- P0055
- P0060
- Catalyst efficiency codes
- Battery voltage codes
Record freeze-frame data before clearing codes.
Step 2: Locate Bank 2 Sensor 2
Confirm:
- Cylinder number one
- Bank 2
- Downstream oxygen sensor
Replacing the wrong oxygen sensor remains one of the industry’s most common mistakes.
Step 3: Inspect Wiring
Check for:
- Melted insulation
- Chafing
- Shorted wiring
- Exhaust contact
- Pinched harness
Step 4: Inspect Connector
Inspect for:
- Moisture
- Corrosion
- Bent terminals
- Loose pins
- Broken locks
Step 5: Check Heater Resistance
Disconnect the oxygen sensor.
Measure heater resistance.
Very low resistance usually indicates an internally shorted heater.
Step 6: Verify Power Supply
Inspect:
- Heater fuse
- Relay
- Battery voltage
- Ground integrity
Step 7: Check for Short to Ground
Using a multimeter, verify the heater control circuit is not shorted directly to ground.
Repair damaged wiring before replacing components.
Step 8: Perform Voltage Drop Testing
Check voltage drop across:
- Heater power wire
- Ground circuit
- Connectors
- Relay contacts
High current often creates abnormal voltage readings.
Step 9: Replace the Sensor if Necessary
If testing confirms a shorted heater element, replace Bank 2 Sensor 2 with an OEM-quality direct-fit oxygen sensor.
Step 10: Verify Repairs
After repairs:
- Clear DTCs.
- Perform a cold start.
- Monitor heater operation.
- Complete a drive cycle.
- Confirm readiness monitors complete.
- Verify P0057 does not return.
Common Repairs and Costs
| Repair | Estimated Cost |
| Oxygen sensor replacement | $150–500 |
| Wiring repair | $100–400 |
| Connector replacement | $75–250 |
| Heater relay replacement | $50–200 |
| Fuse replacement | $10–50 |
| Harness repair | $100–500 |
| ECM replacement | $1,000–2,500+ |
Common Diagnostic Mistakes
Avoid these mistakes:
- Replacing the wrong oxygen sensor
- Ignoring melted wiring
- Assuming the sensor failed without testing
- Installing universal oxygen sensors
- Skipping resistance testing
- Ignoring water intrusion
- Replacing the ECM before testing the circuit
Vehicles Commonly Affected
P0057 commonly appears on:
- Chevrolet
- GMC
- Ford
- Dodge
- Chrysler
- Jeep
- Toyota
- Lexus
- Honda
- Acura
- Nissan
- Infiniti
- Hyundai
- Kia
- Subaru
- Volkswagen
- Audi
- BMW
- Mercedes-Benz
- Volvo
Exact heater circuit designs vary by manufacturer.
How to Prevent P0057
Reduce the likelihood of P0057 by:
- Using OEM-quality oxygen sensors
- Keeping wiring away from exhaust components
- Maintaining heat shields
- Inspecting connectors during exhaust repairs
- Preventing water intrusion
- Repairing damaged harnesses promptly
- Avoiding universal splice-in sensors
Frequently Asked Questions
What does P0057 mean?
P0057 indicates the ECM has detected a low-voltage condition in the heater control circuit for Bank 2 Sensor 2.
Is P0057 serious?
Usually not, but wiring shorts should be repaired quickly to prevent additional electrical damage.
Can I drive with P0057?
Yes.
Most vehicles remain safe to drive.
What causes P0057?
Common causes include:
- Shorted heater element
- Wiring shorted to ground
- Melted wiring
- Damaged connector
- Incorrect replacement sensor
Will replacing the oxygen sensor fix P0057?
Often yes, provided the heater element has failed.
Always inspect the wiring before replacing parts.
Is P0057 the same as P0056?
No.
P0056 is a general heater control circuit fault.
P0057 specifically indicates a low-voltage condition.
Does P0057 affect fuel economy?
Very little.
The downstream oxygen sensor primarily monitors catalyst efficiency.
Can P0057 cause an emissions failure?
Yes.
Incomplete catalyst monitoring and readiness monitors may prevent the vehicle from passing an emissions inspection.
Final Thoughts
The P0057 code indicates the ECM has detected a low-voltage condition in the Bank 2 Sensor 2 oxygen sensor heater control circuit. In most cases, the fault is caused by a shorted heater element, damaged wiring, or a short to ground within the heater circuit.
Begin diagnosis by inspecting the wiring near the catalytic converter, as heat damage is extremely common in this area. After verifying the wiring, test the heater resistance, connectors, fuse, and relay before replacing components. Prompt repairs help restore proper catalyst monitoring, reduce emissions, and ensure the vehicle completes its OBD-II readiness monitors.
Related Articles
Bank 1 Sensor 2 Heater Codes
- P0036 Code Explained: HO2S Heater Control Circuit Bank 1 Sensor 2
- P0037 Code Explained: HO2S Heater Control Circuit Low Bank 1 Sensor 2
- P0038 Code Explained: HO2S Heater Control Circuit High Bank 1 Sensor 2
- P0054 Code Explained: HO2S Heater Resistance Bank 1 Sensor 2
Browse the complete Pro Street diagnostic libraries:
- Complete OBD-II Guide: https://my.prostreetonline.com/dtc-obdii/
- B-Code Guide: https://my.prostreetonline.com/dtc-doctor/b-code-obd-ii-codes/
- C-Code Guide: https://my.prostreetonline.com/dtc-doctor/c-code-obd-ii-codes/
