P0037, a generic OBD-II powertrain diagnostic trouble code related specifically to the oxygen sensor heater control circuit on Bank 1 Sensor 2. This guide explains what P0037 means, where the affected sensor is located, common symptoms and causes, diagnostic steps, multimeter testing, oscilloscope testing, repair options and estimated repair costs.
P0037 does not automatically mean that the oxygen sensor itself has failed. The fault may involve the sensor heater, wiring, connector, fuse, power supply, heater control circuit, or less commonly the ECM.
What Does P0037 Mean?
P0037 indicates that the Engine Control Module (ECM) has detected an abnormally low electrical condition in the heater control circuit of the downstream oxygen sensor on Bank 1.
The oxygen sensor heater allows the sensor to reach its operating temperature more quickly after engine startup. If the heater circuit does not operate correctly, the sensor may take longer to reach its required operating temperature.
The word Low in P0037 refers to an electrical condition detected in the heater control circuit. It does not simply mean that the oxygen sensor is producing a low oxygen-signal voltage.
P0037 Code Definition
P0037
Generic OBD-II Powertrain
HO2S Heater Circuit
Bank 1 Sensor 2
What Are Bank 1 and Sensor 2?
Bank 1 refers to the engine bank containing cylinder number 1. On an inline engine there is normally only one cylinder bank. On a V-type engine, Bank 1 is the side containing cylinder number 1.
Sensor 2 normally refers to the oxygen sensor located downstream of the catalytic converter.
Therefore, P0037 normally concerns the downstream oxygen sensor heater on Bank 1.
Sensor locations and numbering can vary by vehicle design, so always confirm the exact sensor location using the vehicle-specific service information.
Where Is the P0037 Sensor Located?
The oxygen sensor associated with P0037 is normally located in the exhaust system after the catalytic converter on Bank 1.
The sensor wiring is often routed close to the exhaust system. Excessive exhaust heat, physical contact, corrosion or previous repairs can therefore damage the heater circuit wiring.
Engine → Exhaust Manifold → Catalytic Converter → Bank 1 Sensor 2
How Does the P0037 Heater Circuit Work?
The oxygen sensor contains an internal heating element. The vehicle supplies electrical power to the heater circuit and controls or monitors the circuit through the engine control system.
Depending on the vehicle, the heater may receive battery voltage through a fuse while the ECM controls the other side of the circuit. Other designs can use different control strategies.
Because circuit design varies, the exact wiring arrangement must be confirmed with the vehicle wiring diagram.
P0037 Signal Flow
↓
Fuse or Protected Circuit
↓
Bank 1 Sensor 2 Heater
↓
Heater Control Circuit
↓
ECM Heater Driver
↓
Circuit Monitoring
The actual power and control arrangement depends on the vehicle manufacturer and oxygen-sensor design.
Symptoms of P0037
- Check Engine Light illuminated.
- Longer oxygen-sensor warm-up time.
- Increased emissions.
- Possible increase in fuel consumption.
- Delayed closed-loop operation on some vehicles.
- Possible fuel-trim changes.
- Usually little or no noticeable drivability problem.
- Additional oxygen-sensor or heater-related faults may be stored.
Common Causes of P0037
- Failed Bank 1 Sensor 2 oxygen-sensor heater.
- Short to ground in the heater control circuit.
- Damaged heater wiring.
- Open or high-resistance wiring.
- Damaged oxygen-sensor connector.
- Corroded or loose electrical terminals.
- Blown heater fuse where applicable.
- Incorrect heater power supply.
- Exhaust heat damage to the wiring harness.
- Incorrectly installed replacement sensor.
- Incorrect oxygen sensor for the vehicle.
- ECM heater-control driver fault.
How to Diagnose P0037
1. Scan for P0037 and Other Codes
Connect an OBD-II scanner and confirm that P0037 is stored or pending. Record freeze-frame information before clearing any diagnostic codes.
Additional voltage, oxygen-sensor, fuel-system or communication faults may provide useful diagnostic clues.
2. Inspect the Bank 1 Sensor 2 Wiring
Inspect the wiring from the oxygen sensor toward the main harness.
Look for melted insulation, broken wires, exhaust contact, damaged connectors, corrosion, loose terminals and previous wiring repairs.
3. Check the Heater Fuse
If the vehicle uses a dedicated oxygen-sensor heater fuse, inspect it according to the manufacturer's wiring diagram.
If the fuse is blown, determine the cause before installing another fuse. Replacing a fuse repeatedly without identifying the electrical problem can result in further damage.
4. Check Heater Power Supply
Verify that the heater circuit receives the specified voltage under the correct ignition and operating conditions.
Do not assume that every oxygen-sensor heater operates at exactly the same voltage under all conditions.
5. Test Heater Resistance
When specified by the manufacturer, disconnect the oxygen sensor and measure the resistance of the internal heater.
Compare the measurement with the specification for the exact sensor and vehicle.
There is no single universal heater-resistance value that applies to every oxygen sensor.
6. Check for a Short Circuit
Because P0037 indicates a low electrical condition, inspect the heater control circuit for an unintended short to ground or another circuit.
Use the vehicle wiring diagram to identify the correct terminals before testing.
7. Perform Voltage-Drop Testing
A voltage-drop test can help identify high resistance caused by damaged wiring, corrosion, poor terminals or weak electrical connections.
8. Verify the ECM Control Circuit
If the sensor, fuse, power supply, wiring and connectors are confirmed to be correct, test the ECM heater-control circuit according to the manufacturer's diagnostic procedure.
Do not replace the ECM based on P0037 alone.
P0037 OBD2 Live Data
Depending on the vehicle and diagnostic scanner, useful parameters may include:
- Bank 1 Sensor 2 oxygen-sensor information.
- Heater status.
- Heater current or duty cycle where supported.
- Engine coolant temperature.
- Engine RPM.
- Short-term fuel trim.
- Long-term fuel trim.
- Closed-loop status.
Live Data can provide useful information about sensor operation, but P0037 is primarily an electrical heater-circuit fault. Direct circuit testing may therefore be necessary.
P0037 Multimeter Testing
A digital multimeter can help test the P0037 heater circuit. The exact procedure depends on the vehicle and sensor design.
Identify heater terminals using the wiring diagram.
Measure heater resistance when specified.
Verify heater power supply.
Check continuity and unwanted shorts.
Perform voltage-drop testing where appropriate.
Always compare measurements with the manufacturer's specifications for the exact vehicle.
P0037 Oscilloscope Testing
An oscilloscope can be useful when the heater control circuit is intermittent or when the vehicle uses a PWM-controlled heater circuit.
Depending on the vehicle, the control signal may appear as a switched or pulse-width-modulated waveform.
▔▔▔▔▔▔▔▔▔▔▁▁▁▁▁▁▁▁▁▁▔▔▔▔▔▔▔▔
The waveform shown is conceptual only. Always compare the actual signal with the manufacturer's specification.
How to Fix P0037
The correct repair depends on what testing identifies as the cause.
- Replace a failed Bank 1 Sensor 2 oxygen sensor when the heater is confirmed defective.
- Repair damaged heater wiring.
- Repair or replace damaged connectors.
- Repair poor electrical terminals.
- Replace a blown fuse after identifying why it failed.
- Repair the heater power supply.
- Repair a shorted heater control circuit.
- Repair high-resistance connections.
- Repair the ECM heater-control circuit when confirmed faulty.
Do not replace the oxygen sensor simply because P0037 is present. Test the complete heater circuit first.
How Much Does It Cost to Repair P0037?
Approximately $50–$150+
Approximately $30–$150+
Approximately $50–$250+
Approximately $100–$400+
Can cost considerably more depending on the vehicle.
These are general estimates only. Actual repair costs depend on the vehicle, sensor type, parts prices, labor rates, accessibility and the actual cause of the fault.
Is P0037 Serious?
P0037 is usually not an immediate engine-damage fault, but it should be diagnosed and repaired.
A failed downstream oxygen-sensor heater can delay sensor operation and may increase emissions. Other electrical problems in the same circuit can also become more serious if they remain unrepaired.
Can You Drive With P0037?
In many cases, limited driving is possible if the engine is operating normally and there are no other serious symptoms.
However, continued driving with the Check Engine Light illuminated allows the underlying electrical fault to remain unresolved.
If the vehicle develops misfires, loss of power, overheating or additional warning lights, stop driving when safe and have the vehicle inspected.
Common Repair Mistakes With P0037
- Replacing the oxygen sensor without testing the heater circuit.
- Assuming "Low" means low oxygen-sensor signal voltage.
- Ignoring the heater fuse.
- Failing to inspect wiring near the hot exhaust.
- Using the wrong replacement sensor.
- Using an incorrect heater-resistance specification.
- Ignoring connector corrosion.
- Replacing the ECM before testing the circuit.
- Clearing the code without confirming the repair.
Recommended Diagnostic Tools for P0037
Confirm P0037, check related diagnostic information and monitor supported data.
Test heater resistance, power, continuity and voltage drop.
Evaluate intermittent or PWM heater-control signals where applicable.
Identify heater power, control, ground and connector circuits.
P0037 Vehicle Applications
P0037 is a generic OBD-II powertrain code and can occur on vehicles from many manufacturers.
The generic meaning of the code remains consistent, but the oxygen-sensor design, heater wiring, connector configuration, fuse arrangement, control strategy and diagnostic specifications can vary significantly between vehicles.
Always use vehicle-specific service information when performing electrical diagnosis.
Related OBD-II Codes
P0037 is the primary code covered by this article. The codes below are different diagnostic trouble codes that may be related to the same oxygen-sensor heater or oxygen-sensor circuit. They are included only as supporting references and are not the primary subject of this page.
HO2S Heater Control Circuit — Bank 1 Sensor 2
HO2S Heater Control Circuit High — Bank 1 Sensor 2
O2 Sensor Heater Circuit Malfunction — Bank 1 Sensor 2
O2 Sensor Circuit Low Voltage — Bank 1 Sensor 2
O2 Sensor Circuit High Voltage — Bank 1 Sensor 2
HO2S Heater Resistance — Bank 1 Sensor 2
These codes have different definitions and should not be interpreted as the same fault as P0037. If another code is stored, diagnose that code separately using its own definition and vehicle-specific test procedure.
Frequently Asked Questions About P0037
Does P0037 mean the oxygen sensor is bad?
Not necessarily. P0037 identifies a low electrical condition in the heater control circuit. The cause may be the sensor heater, wiring, connector, fuse, power supply, control circuit or ECM.
What is Bank 1 Sensor 2?
Bank 1 is the engine bank containing cylinder number 1. Sensor 2 normally refers to the oxygen sensor located downstream of the catalytic converter.
Can a blown fuse cause P0037?
Yes, where the oxygen-sensor heater circuit is protected by a fuse. The reason for the blown fuse should be identified before installing another fuse.
Can wiring cause P0037?
Yes. Damaged wiring, short circuits, high resistance, poor terminals and exhaust heat damage can interfere with the heater circuit.
Can P0037 cause poor fuel economy?
It can contribute to increased fuel consumption or altered emissions behavior on some vehicles, although the effect on drivability is often limited because Sensor 2 is downstream of the catalytic converter.
Can I drive with P0037?
Usually, limited driving is possible if the engine operates normally. However, the electrical fault should be diagnosed and repaired.
How do I fix P0037?
Confirm P0037, inspect the Bank 1 Sensor 2 wiring and connector, check the heater fuse and power supply, test heater resistance where applicable, inspect the control circuit and replace the sensor only when testing confirms that it has failed.
Is P0037 a generic OBD-II code?
Yes. P0037 is a generic OBD-II powertrain diagnostic trouble code. The exact circuit design and diagnostic procedure vary by manufacturer and vehicle.
Final Takeaway
P0037 indicates a low electrical condition in the Bank 1 Sensor 2 oxygen-sensor heater control circuit.
The most reliable diagnosis is to test the complete heater circuit instead of automatically replacing the oxygen sensor. Check the fuse, power supply, connector, wiring, heater resistance, control circuit and ECM operation in the correct sequence.
Because oxygen-sensor heater circuits differ between vehicles, always use the exact wiring diagram and specifications for the vehicle being diagnosed.