O2 Sensor Heater Control Circuit High (Bank 1 Sensor 2)
The P0038 code indicates that the powertrain control module (PCM) has detected a high voltage condition in the heater control circuit for the downstream oxygen sensor (Bank 1, Sensor 2). This sensor monitors catalytic converter efficiency. The heater element helps the sensor reach operating temperature quickly. A high voltage reading suggests a short to power, a faulty sensor, or a wiring issue. This can cause the sensor to not heat properly, leading to incorrect readings and potential emissions problems.
01. Most Common Causes
- Shorted or damaged wiring in the heater circuit
- Faulty oxygen sensor (Bank 1 Sensor 2)
- Blown heater circuit fuse
- Corroded or loose connector at the sensor
- Failed PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Failed emissions test
- Decreased fuel economy
- Rough idle or hesitation (less common)
03. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for other codes.
Step 2: Visually inspect the wiring and connector for Bank 1 Sensor 2 for damage, corrosion, or shorts.
Step 3: Test the heater circuit voltage and resistance with a multimeter; compare to manufacturer specs.
Step 4: Check the heater circuit fuse and replace if blown.
Step 5: If wiring and fuse are good, replace the oxygen sensor.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
Yes, but it may cause poor fuel economy and increased emissions. It's best to fix it soon to avoid failing an emissions test.
How much does it cost to fix?▼
Typically $50-$150 for a DIY replacement of the oxygen sensor; labor adds $50-$100 if done by a shop.