P2245–P2249 O2 Sensor Reference Voltage Circuit Low Bank 1 Sensor 1
The voltage on this circuit is sitting near zero. Typically a short to earth, or a sensor that has failed to its low end.
Can you drive it? The engine light will stay on and the car may run in a reduced-power mode. Read the freeze-frame data to see the conditions the fault was logged under.
Which code is which
Same fault, different cylinder or bank — diagnosed the same way. Several set together usually means one shared cause.
| Code | Definition | Severity |
|---|---|---|
P2245 | O2 Sensor Reference Voltage Circuit Low Bank 1 Sensor 1 | Investigate soon |
P2249 | O2 Sensor Reference Voltage Circuit Low Bank 2 Sensor 1 | Investigate soon |
The definition
P2245: O2 Sensor Reference Voltage Circuit Low Bank 1 Sensor 1.
P2245 is a manufacturer-specific powertrain code (the engine or gearbox). Its meaning is set by the carmaker rather than by the SAE standard, so a generic OBD-II reader will often show it as an unknown code or misread it.
What to check first
Cheapest and fastest checks first:
- Unplug the sensor. If the reading jumps to full scale, the wiring is fine and the sensor has failed low.
- Check the sensor's 5V supply and its earth before condemning the sensor itself.
What actually causes this on a VAG
Again the upstream wideband lambda sensor, before the catalytic converter on the cylinder 1 side. Here its reference circuit is being pulled low, towards earth, rather than reading normally. Because that is a short rather than a break, moisture or damaged insulation is the usual culprit. Expect an engine light, default fuelling and slightly worse economy while it is present.
Most likely causes, in order
- Water or corrosion in the sensor connector. Damp bridging two pins reads to the ECU as a dead short, and it is the classic cause of this code. The upstream sensor's plug usually clips to a bracket at the back of the engine near the bulkhead, which is where water runs off if the plenum drains under the windscreen are blocked with leaves. Open, dry and inspect the plug - and clear the drains at the same time, because a connector that has flooded once will flood again.
- Chafed lead shorting to earth. Follow the sensor lead and look where it passes the block, a bracket or an exhaust heat shield. A melted or rubbed-through spot with a matching witness mark on the metal behind it is the classic find, and the exhaust side of the engine gives it plenty of opportunity.
- The sensor shorted internally. Confirm with a test rather than a purchase. With the ignition off, unplug the sensor, then clear the codes and let the ECU look again. If the fault returns as a low or short type with nothing connected, the problem is in the loom or the ECU. If it changes to an open-circuit type instead, the sensor itself is the suspect. Expect the test to set an additional sensor code of its own while the plug is off - that is normal and clears once it is reconnected.
- Wiring back to the ECU or the ECU's sensor supply. Uncommon, and only worth reaching once the connector, lead and sensor have been ruled out. An ECU replacement on a VAG needs coding and immobiliser matching, so it is not a step to take on suspicion.
Worth knowing: If water is found in the plug, fixing the drain that let it in matters as much as fixing the connection - otherwise the replacement sensor corrodes in the same way within a season. Two things worth knowing when the sensor does come out: these seize into the exhaust and are best removed with the engine warm rather than stone cold or fully hot, using a proper lambda socket, and most genuine replacements arrive with compound already on the threads, so do not add more and never let any of it near the sensor tip. And keep silicone sealant and silicone sprays away from the intake, the exhaust threads and the sensor itself - silicone poisons lambda sensors permanently, and a new one will fail the same way.
Reading the code is the easy part
A code names the circuit that complained. What tells you why is watching the sensor behind it while the engine runs — and that is where a code reader stops and a diagnostic tool starts.
VAGPULSE reads every module in a VW, Audi, Skoda or SEAT — not just the engine — shows the live measuring blocks behind this fault, gives you the freeze-frame conditions it was logged under, and clears it once you have fixed it. It also does what a generic OBD reader cannot on a VAG: service resets, coding, adaptations, and Stage 1–3 flashing with your original file saved first.
$249 once. No subscription, unlimited cars. Windows 10/11.
See VAGPULSE — $249 Look up another codeSoftware downloads instantly · cable ships September 30 · cable guarantee — refund if it won't connect
Prefer to work on your phone? The VAGPULSE Android app is a free download and its demo mode runs against a sample car with no hardware at all, so you can see exactly what it reads before spending anything. Reading your car with it needs the VAGPULSE cable, which comes with the licence.
Common questions
What does P2245 mean?
P2245 means O2 Sensor Reference Voltage Circuit Low Bank 1 Sensor 1. The voltage on this circuit is sitting near zero. Typically a short to earth, or a sensor that has failed to its low end.
Can I drive with P2245?
The engine light will stay on and the car may run in a reduced-power mode. Read the freeze-frame data to see the conditions the fault was logged under.