O2 Sensor Heater Circuit Low (Bank 1 Sensor 2)
The P0037 code indicates that the powertrain control module (PCM) has detected a low voltage or current in the heater control circuit of the downstream oxygen sensor (Bank 1, Sensor 2). This sensor monitors catalytic converter efficiency, and its internal heater helps it reach operating temperature quickly. A low circuit condition typically means the heater resistance is too high, there's a short to ground, or the sensor is faulty. This can lead to increased emissions and reduced fuel economy.
01. Most Common Causes
- Faulty oxygen sensor (Bank 1 Sensor 2)
- Blown heater fuse
- Open or shorted heater circuit wiring
- Corroded or damaged connector
- Faulty PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Failed emissions test
- Possible slight decrease in fuel economy
- No noticeable drivability issues in most cases
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect the O2 sensor connector and wiring for damage, corrosion, or loose connections.
Step 3: Check the heater circuit fuse (usually in the engine bay fuse box).
Step 4: Using a multimeter, measure resistance between the heater circuit pins at the sensor connector (typically 5-10 ohms). If out of range, replace the sensor.
Step 5: Verify power and ground at the sensor connector with the ignition on. If missing, repair wiring or check PCM output.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
Yes, the vehicle is generally safe to drive, but it may fail an emissions test and fuel economy could suffer. It's best to repair it soon.
How much does it cost to fix?▼
Typically $100-$250 including parts and labor. The oxygen sensor itself costs $30-$100, and labor is about $50-$150.