O2 Sensor Heater Control Circuit Malfunction (Bank 2 Sensor 2)
The P0056 code indicates a problem with the heater control circuit for the oxygen sensor located after the catalytic converter on bank 2 of the engine. The Powertrain Control Module (PCM) monitors the current draw of the heater element and detects an open or short circuit. This can cause the sensor to warm up slowly, leading to inaccurate readings and increased emissions.
01. Most Common Causes
- Faulty oxygen sensor (Bank 2 Sensor 2)
- Open or shorted heater circuit wiring
- Blown fuse for the O2 sensor heater
- Corroded or damaged connector
- Faulty 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: Scan for codes and record freeze frame data.
Step 2: Visually inspect the O2 sensor wiring and connector for damage or corrosion.
Step 3: Check the O2 sensor heater fuse and relay.
Step 4: Measure resistance of the heater circuit at the sensor connector (typically 2-10 ohms).
Step 5: Test for voltage and ground at the heater circuit with the key on.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
Yes, but it may cause increased emissions and reduced fuel economy. It's best to repair 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, or $150-$300 at a shop including labor.