OBD-II code · Powertrain (generic, extended)
P2249 O2 Sensor Reference Voltage Circuit Low (Bank 2 Sensor 1)
Bank 2 counterpart to P2245. The reference voltage on bank 2, sensor 1 is below the lower threshold — typically a short to ground or failed ECU output.
Is it safe to drive with P2249?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyReference line shorted to ground
- Less likelyECU reference output failed
- Less likelyConnector pins corroded - high contact resistance
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.5–2 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Oxygen Sensor Upstream B2, Oxygen Sensor Wiring
Related codes
- P2245O2 Sensor Reference Voltage Circuit Low (Bank 1 Sensor 1)
- P2248O2 Sensor Reference Voltage Circuit Range/Performance (Bank 2 Sensor 1)
- P2250O2 Sensor Reference Voltage Circuit High (Bank 2 Sensor 1)
- P22B0O2 Sensor Reference Voltage Circuit Low (Bank 1 Sensor 2)
- P22BDO2 Sensor Reference Voltage Circuit Low (Bank 2 Sensor 2)
- P2246O2 Sensor Reference Voltage Circuit High (Bank 1 Sensor 1)
- P2247O2 Sensor Reference Voltage Circuit (Bank 2 Sensor 1)
- P224ANOx Sensor Heater Resistance (Bank 1 Sensor 1)
- P224BNOx Sensor Heater Resistance (Bank 1 Sensor 2)
- P224CAlternative Fuel Tank Shutoff Valve A Control Circuit/Open
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.