P0037: Ho2S Heater Control Circuit Low (Bank 1 Sensor 2)
P0037 means the engine computer has found a low-voltage problem in the heater circuit for the downstream oxygen sensor on bank 1. The most common fix is replacing the oxygen sensor or repairing damaged heater wiring, which typically costs about $150 to $450 at an independent shop.
- Severity
- Moderate
- Can I drive?
- Drive with caution
- DIY?
- Possible with some experience
- Repair cost range
- $90 – $900
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What does P0037 mean?
This code points to the heated oxygen sensor after the catalytic converter on bank 1, also called Bank 1 Sensor 2. That sensor has a small heater inside it so it can reach operating temperature quickly and help the computer monitor emissions. When the heater circuit voltage is too low, the sensor may warm up too slowly or not at all. That can keep the engine light on and may affect fuel control and catalyst monitoring.
Common symptoms
- Check engine light on
- Possible stored emission codes
- Failed readiness monitor
- Slight drop in fuel economy
- Rough running is uncommon
- May pass or fail inspection depending on readiness
Causes, fixes and costs
P0037: Ho2S Heater Control Circuit Low (Bank 1 Sensor 2)
General guide for most cars. Your car may differ.
This usually will not strand the car, but it can keep the emissions system from working correctly and may cause an inspection failure. Stop driving if the engine runs badly, the fuse keeps blowing, or you smell burning wiring.
Most likely causes
- 1
Failed Bank 1 Sensor 2 oxygen sensorHigh
If the check engine light is on by itself and the heater circuit code returns after clearing, the heater inside the sensor may be open or shorted. This is most likely if the sensor is original or high-mileage.
Quick check: Inspect the sensor connector and measure heater resistance if you have a multimeter, or have the sensor tested at a shop.
- 2
Damaged wiring or connectorHigh
Intermittent codes, a recent exhaust repair, or visible heat damage near the exhaust point to a broken wire, loose plug, or corroded terminals. Wiring faults often come and go with bumps or engine movement.
Quick check: Look for melted insulation, rubbed-through wiring, loose pins, or corrosion at the sensor connector.
- 3
Blown fuse or relay for the heater circuitMedium
If the sensor lost power completely or there are multiple heater-related codes, a shared fuse or power feed may be open. This is more likely if the code appeared suddenly.
Quick check: Check the under-hood fuse box for any blown O2 heater or engine control fuses.
- 4
PCM driver issueLow
If the sensor and wiring test good but the heater still has no command or power, the control module may not be switching the circuit correctly. This is uncommon and usually diagnosed only after other checks fail.
Quick check: Have a shop verify power, ground, and PCM command before replacing the module.
Can you fix it yourself?
Possible with some experience
Difficulty: Moderate. A DIY fix is possible if you can safely get under the car, inspect wiring, and use a multimeter. You may need a replacement upstream/downstream oxygen sensor socket, penetrating oil, and the correct Bank 1 Sensor 2 sensor for your vehicle.
Show the stepsHide the steps
- Confirm the code and clear it to see if it returns
- Inspect the sensor harness and connector for heat or damage
- Check the related fuse for power to the heater circuit
- Test heater resistance and power at the sensor if possible
- Replace the oxygen sensor if the heater is open or shorted
- Repair any melted or broken wiring and secure the harness away from the exhaust
- Clear codes and drive the car through a full warm-up cycle
- Recheck for pending or returning codes
Estimated repair cost
$150 – $350
Replace Bank 1 Sensor 2 oxygen sensor: parts ~$50-$180, labor ~$100-$170
- Repair oxygen sensor wiring or connector$120 – $300
- Replace blown fuse or relay and inspect circuit$90 – $180
- PCM diagnosis and possible replacement$300 – $900
Prices vary by vehicle, engine layout, rust, and local labor rates.
Frequently asked questions
Can I drive with P0037?
Usually yes, for short trips, but get it checked soon. The car may drive normally while still failing emissions monitoring or inspection.
Will P0037 clear itself?
Sometimes it may go away temporarily if the fault is intermittent, but the code usually returns until the underlying problem is fixed. Clearing the code does not repair it.
Is P0037 the same as a bad catalytic converter?
No. P0037 is for the heater circuit of the downstream oxygen sensor, not the converter itself, though a bad sensor can sometimes affect catalyst monitoring.
Can a bad oxygen sensor cause this code?
Yes. A failed heater inside Bank 1 Sensor 2 is one of the most common causes, especially on older sensors or after many heat cycles.
Will this code cause a failed inspection?
It can, because the check engine light is on and the emissions monitors may not complete. Some states will fail a vehicle for either condition.
Related codes
- P0135 O2 Sensor Heater Circuit (Bank 1 Sensor 1)
- P0036 Ho2S Heater Control Circuit (Bank 1 Sensor 2)
- P0038 Ho2S Heater Control Circuit High (Bank 1 Sensor 2)
- P0141 O2 Sensor Heater Circuit (Bank 1 Sensor 2)
- P0136 O2 Sensor Circuit (Bank 1 Sensor 2)
- P0420 Catalyst System Efficiency Below Threshold (Bank 1)
Related problems
This guide covers most cars and is general advice, not an inspection. Prices are typical US independent-shop ranges and vary by region, car and shop. If your brakes, steering or a warning light feel unsafe, stop driving and contact a mechanic.