P2243–P2247 O2 Sensor Reference Voltage Circuit/Open Bank 1 Sensor 1
The circuit is broken somewhere - a cut wire, a corroded pin or an unplugged connector means the signal never arrives.
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 |
|---|---|---|
P2243 | O2 Sensor Reference Voltage Circuit/Open Bank 1 Sensor 1 | Investigate soon |
P2247 | O2 Sensor Reference Voltage Circuit/Open Bank 2 Sensor 1 | Investigate soon |
The definition
P2243: O2 Sensor Reference Voltage Circuit/Open Bank 1 Sensor 1.
P2243 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:
- Check the connector is fully seated and the locking tab is engaged. A half-seated plug is the single most common cause of an open circuit.
- Back-probe the pins and check continuity from the part back to the module connector.
- Inspect for a pushed-back or corroded terminal - the wire looks fine but the pin has backed out of the housing.
What actually causes this on a VAG
Bank 1 sensor 1 is the upstream lambda sensor - the one screwed into the exhaust before the catalytic converter, on the side of the engine that contains cylinder 1. On a four-cylinder there is only one, but on a V6 or V8 check which side cylinder 1 is on for your specific engine before starting work: on some VAG V engines it is not the side you would guess, and getting it wrong means replacing a perfectly good sensor. Modern VAG upstream sensors are wideband types - VAG's own software calls them linear or broadband sensors - with five or six wires. One of those wires carries a reference voltage the ECU supplies and holds steady, and everything the sensor reports is measured against it. P2243 means the ECU sees that circuit as open, with nothing there at all. The mixture reading becomes meaningless, so the engine falls back on a default fuelling map: engine light, noticeably worse economy, sometimes a flat spot or a hesitation. Older VAG control units log the identical fault under their own naming, as a linear oxygen sensor reference voltage open circuit, so a workshop may quote you a different code number for the same problem.
Most likely causes, in order
- Damaged sensor lead or connector. By far the most likely, and free to inspect. The lead runs past very hot exhaust parts and commonly melts against a heat shield, chafes on a bracket, or gets trapped and pulled when the downpipe, turbo or gearbox has been out. Inspect the whole run rather than just the ends, and check the plug is fully latched with no pin pushed back into the housing - a backed-out pin reads to the ECU exactly like a severed wire.
- An aftermarket or spliced-in universal sensor. Check this early if any sensor has been fitted recently, because it costs nothing to look at what is on the car. VAG ECUs are fussy, and cut-and-join universal sensors frequently throw exactly this family of reference-voltage faults even when brand new, because the reference and calibration circuits are not wired or valued the way the ECU expects. Fit the correct part with its factory plug rather than splicing.
- The sensor has failed internally. An open in the sensor's own reference circuit - inside the body or in its moulded pigtail - gives the same reading as a broken loom. Worth noting that this is an electrical failure, not the gradual exhaust-side poisoning that ruins a sensor's mixture readings; poisoning shows up as signal and response faults, not as an open reference circuit. Confirmed by fitting a known-good correct sensor once the wiring has been proved sound.
- Wiring back to the ECU, or the ECU itself. Genuinely rare and last on the list. Only reasonable once the sensor lead, connector and sensor have each been checked, since an ECU brings coding and immobiliser work with it.
Worth knowing: If several codes for the same sensor appear together - heater, signal and reference voltage all at once - that is one damaged multi-core lead or one wet connector, not three separate failures. Repairing the wiring and clearing the codes first will often make the whole set disappear without buying a sensor at all. One warning if you are testing it yourself: do not go probing a wideband sensor's pins at random with a multimeter. It is easy to damage one that way and turn a wiring fault into a wiring fault plus a dead sensor. Back-probe the ECU side of the connector, or leave it to someone with the wiring diagram in front of them.
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.
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Common questions
What does P2243 mean?
P2243 means O2 Sensor Reference Voltage Circuit/Open Bank 1 Sensor 1. The circuit is broken somewhere - a cut wire, a corroded pin or an unplugged connector means the signal never arrives.
Can I drive with P2243?
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.