P0037🌫 Emissions / oxygen sensorsDrive with caution, fix soon

P0037: HO2S Heater Control Circuit Low (Bank 1, Sensor 2) (Meaning, Causes, Fixes)

Reviewed 2026-10-24 · Based on 2 cited source(s)

What P0037 means

Bank 1 Sensor 2 is the second oxygen sensor back on the side of the engine with cylinder #1 (an inline engine has only Bank 1), normally mounted after the catalytic converter. OBD-Codes.com explains that the engine computer (PCM) uses this sensor mainly to monitor how well the catalytic converter is working. The sensor has a built-in electric heater that brings it up to operating temperature quickly. According to OBD-Codes.com, vehicles control that heater one of two ways: either the PCM switches the 12-volt feed (directly or through an oxygen sensor relay) and the heater is grounded to the vehicle, or a fused 12-volt feed is always live with the key on and the PCM switches the ground side. If the PCM detects an abnormally low voltage on the heater circuit, P0037 may set. RepairPal describes it more simply: the PCM sets P0037 when it detects the heater wire is not operating. Nissan's wording, per OBD-Codes.com, is 'Heated oxygen sensor 2 Bank 1, heater voltage low'. P0141 is the general heater circuit code for this same sensor, P0038 is the circuit-high version, and P0031 is the same fault on the front (Sensor 1) sensor.

Severity: can I keep driving?

Drive with caution, fix soon

Usually drivable. RepairPal rates P0037 Moderate: not an immediate safety threat, but get it diagnosed within a reasonable time. OBD-Codes.com says there will likely be no symptoms other than the check engine light, but a car with an active check engine light will likely fail an OBD2 emissions inspection.

Common symptoms

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

  1. Failed heater element inside the Bank 1 Sensor 2 oxygen sensor (both sources; RepairPal calls it oxygen sensor failure)
  2. Physical damage to the oxygen sensor (OBD-Codes.com)
  3. Heater control circuit, or voltage feed depending on the system, shorted to ground (OBD-Codes.com; RepairPal lists a wiring issue)
  4. Failed oxygen sensor heater driver inside the engine computer (PCM) (both sources list PCM failure)

Diagnostic steps you can do

⚠ Before you start

Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.

  1. Read all stored codes. If P0037 shows up alongside other heater codes such as P0031 or P0141, check a shared heater fuse or relay before replacing sensors.
  2. Visually inspect the Bank 1 Sensor 2 sensor (after the catalytic converter, cylinder #1 side) and its wiring harness. Repair any damage and make sure the wiring is routed away from the exhaust (OBD-Codes.com).
  3. Unplug the sensor and, with the key on and engine off, check for 12 volts at the heater feed in the harness connector, or for ground, depending on how your system is wired (OBD-Codes.com).
  4. Check that the heater control (ground) circuit is intact.
  5. Remove the sensor, inspect it for damage, and if you have the resistance specification, measure the heater element with an ohmmeter. Infinite resistance means the heater is open and the sensor needs replacing (OBD-Codes.com).

Typical fixes

Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.

🛠 When to call a pro

  • The code returns right after a new sensor is fitted, which points to wiring, the heater feed or the computer
  • You need a wiring diagram to tell whether your vehicle switches the heater's 12-volt feed or its ground
  • The sensor is seized in the exhaust pipe

Where to buy

Plain search links. Always match parts to your exact year, make, model and engine.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

Is P0037 the front or rear oxygen sensor?

The rear one. Sensor 2 is the second sensor back on Bank 1, normally after the catalytic converter. OBD-Codes.com says the computer uses it mainly to check catalytic converter efficiency, which is why a fault here usually doesn't change how the engine runs.

What's the difference between P0141 and P0037?

Both are about the heater in the Bank 1 Sensor 2 oxygen sensor. P0141 is the general heater circuit malfunction code, while P0037 specifically means the computer saw a low voltage on the heater control circuit. P0038 is the high-voltage version.

Do the sources agree on the symptoms?

Not entirely. OBD-Codes.com says there will likely be no symptoms other than the check engine light. RepairPal lists decreased engine performance and increased fuel consumption. Neither treats it as a safety problem, and RepairPal rates it Moderate.

Sources

  1. OBD-Codes.com: P0037 HO2S Heater Control Circuit Low (Bank 1 Sensor 2), by Dale Toalston, ASE
  2. RepairPal: P0037 HO2S Heater Control Circuit Low (rated Moderate)

Last reviewed 2026-10-24. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.