O2 Sensor Reference Voltage Circuit Open Bank 1 Sensor 1
The P2243 code indicates an open circuit in the reference voltage supply to the oxygen sensor located before the catalytic converter on bank 1 (engine side with cylinder 1). The sensor requires a 5V reference signal from the ECU to operate; an open circuit prevents the sensor from functioning, causing the ECU to detect a fault. This can lead to incorrect air-fuel ratio adjustments, reduced fuel economy, and increased emissions.
1. Most Common Causes
- Faulty or degraded front oxygen sensor (Bank 1, Sensor 1)
- Open or short-to-ground in the reference voltage circuit
- Reference voltage circuit shorted to battery voltage
- Corroded, loose, or damaged O2 sensor connector
- Broken or high-resistance wiring in the harness
- Internal ECM/PCM failure causing incorrect reference voltage
- Poor O2 sensor ground connection
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Poor fuel economy
- Rough idle or hesitation during acceleration
- Failed emissions test
3. Step-by-Step Diagnosis
Step 1: Use a scan tool to confirm P2243 and check for other related codes.
Step 2: Visually inspect the O2 sensor wiring and connector for damage, corrosion, or loose connections.
Step 3: With the ignition on, measure voltage at the sensor connector between the reference voltage pin and ground; should be approximately 5V. If not, check the circuit back to the ECU.
Step 4: If voltage is present, test the sensor's internal resistance; replace if out of spec.
Step 5: Check fuses and relays related to the O2 sensor circuit.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
You can drive short distances, but it may cause poor performance and increased emissions. Prolonged driving can damage the catalytic converter.
How much does it cost to fix?▼
Typically $50-$150 for diagnosis and repair, depending on the cause. Sensor replacement costs $30-$100 plus labor.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.