O2 Sensor Reference Voltage Circuit Low Bank 2 Sensor 1
The P2249 code indicates that the oxygen sensor (O2S) for Bank 2, Sensor 1 has a low reference voltage circuit. This sensor is located upstream of the catalytic converter on the engine bank that does not contain cylinder #1. The reference voltage is typically 5 volts supplied by the powertrain control module (PCM). A low voltage condition can be caused by a faulty sensor, wiring issues, or a PCM problem. This affects the air-fuel ratio feedback, potentially leading to poor fuel economy and increased emissions.
1. Most Common Causes
- Faulty oxygen sensor (Bank 2, Sensor 1)
- Open or shorted wiring in the sensor circuit
- Corroded or damaged connector
- Failed PCM (rare)
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Poor fuel economy
- Rough idle or hesitation
- Failed emissions test
3. Step-by-Step Diagnosis
Step 1: Use a scan tool to verify the code and check for other related codes.
Step 2: Inspect the wiring and connector for Bank 2, Sensor 1 for damage, corrosion, or loose connections.
Step 3: Measure the reference voltage at the sensor connector (should be ~5V with key on). If low, check the circuit back to the PCM.
Step 4: If voltage is correct, test the sensor's heater and signal circuits per manufacturer specs.
Step 5: Replace the oxygen sensor if all wiring checks out.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
You can drive short distances, but it may cause poor fuel economy and increased emissions. Prolonged driving could damage the catalytic converter.
How much does it cost to fix?▼
Typically $150-$300 for parts and labor, depending on the vehicle and shop rates.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.