P2243: O2 Sensor Reference Voltage Circuit/Open (Bank 1 Sensor 1)
Quick Answer
Safe to drive (short-term)
P2243 means the engine computer found an open circuit on the reference voltage line of the first oxygen sensor on bank 1, the one in front of the catalytic converter. The computer supplies this reference voltage to sensors that need it, such as the heated wideband (air/fuel ratio) sensor Saab documents for this code, so the sensor type depends on the make. The cause is usually a broken wire, a bad connector or a failed sensor, so check the wiring before buying parts.
- Severity
- Moderate · Emissions
Up to €400, depending on your car.
A scan shows whether P2243 is really stored on your car, which codes sit next to it and how urgent each one is.
A scan needs a Bluetooth OBD2 adapter (Bluetooth LE on iPhone), about €25-60; the built-in demo runs without one. See which adapter to buy
What does P2243 mean?
P2243 is a emissions-related diagnostic trouble code classified as moderate severity.
What are the symptoms of P2243?
- Check engine light on
- Higher fuel consumption than usual
- Rough idle or hesitation on some cars, because the mixture feedback is lost
- Loss of power or a flat feel under load on some cars
- Failed emissions test or readiness monitors that will not complete
- Other oxygen sensor codes stored with it, such as a heater or no-activity code
What causes P2243?
Damaged, chafed or corroded wiring between the sensor and the engine computer, including the reference voltage wire
: high
Loose, corroded or heat-damaged sensor connector
: high
Failed upstream air/fuel ratio (wideband) sensor
: high
Blown fuse in the sensor's power supply, on cars where it is fused separately
: low
Water or oil in the connector after a wash or a leak
: low
Fault in the engine computer (rare, rule out everything else first)
: low
Is it safe to drive with P2243?
Generally yes, for short-term driving. The car usually drives, but the engine computer loses the mixture feedback from this sensor, so fuel use and emissions can rise. Have the wiring and sensor checked within a few days rather than leaving it for weeks. If the engine runs rough, stalls or loses power, stop driving and get it looked at sooner.
How do you diagnose P2243?
- Read all stored codes and the freeze frame. Heater codes (P0030 to P0032 family), P0134 or lean and rich sensor codes stored alongside point to the same sensor or its wiring. A generic OBD2 reader shows the codes, the freeze frame and, if the car reports it, the live sensor reading
- Confirm which type of sensor your car has before you measure anything. A wideband sensor is read as a lambda or equivalence-ratio value and uses a more complex connector. A classic narrowband sensor swings between about 0.1 and 0.9 V and makes its own signal, so it normally does not use this reference line
- If the sensor has its own fuse in the engine bay fuse box, check it first. It costs almost nothing and a blown fuse can look like an open circuit
- Unplug the sensor connector and inspect it for corrosion, bent or pushed-back pins and heat damage. Follow the harness back along the exhaust for rubbed, melted or chewed insulation
- With the ignition on and the sensor unplugged, measure the reference voltage wire at the harness side against the car's wiring diagram, and the low-reference wire too if the diagram shows one. Expected values differ by make, so use the manual rather than a figure from the web
- If the harness checks out and the sensor still shows the fault, replace the upstream sensor with a correct-type part, clear the code and road-test. The computer usually checks this circuit only once the sensor heater is up to temperature, so allow a full warm-up
- If a new sensor and a good harness do not clear it, a workshop can check the engine computer's sensor connector pins. A generic reader cannot test the sensor driver circuit itself
How much does P2243 cost to fix?
| Repair | Parts Cost | Labor Cost | Total Estimate | DIY Difficulty |
|---|---|---|---|---|
| Clean and reseat the sensor connector | €0–€10 | €0–€40 | €0–€50 | Easy |
| Replace the sensor fuse (where the sensor has its own) | €1–€10 | €0–€40 | €1–€50 | Easy |
| Repair sensor wiring or connector | €5–€40 | €60–€180 | €65–€220 | Moderate |
| Replace the upstream air/fuel ratio (wideband) sensor | €80–€280 | €40–€120 | €120–€400 | Moderate |
| Extended diagnosis with wiring diagram and meter | €0–€0 | €60–€130 | €60–€130 | Professional |
Prices estimated as of October 2026. Costs vary by region, vehicle, and shop.
P2243 on specific vehicles
P2243 on Saab
Saab 9-5
P2243 on Mazda
Related diagnostic codes
Common questions about P2243
- What does P2243 mean?
- P2243 means the engine computer detected an open circuit on the reference voltage line of the bank 1, sensor 1 oxygen sensor. In plain terms the computer cannot complete the circuit it uses to power and read the sensor, so it loses the mixture feedback from that sensor. A broken wire, a bad connector or a failed sensor are the usual reasons.
- Is P2243 a wideband sensor code?
- It applies to oxygen sensors that need a reference voltage from the computer. Saab's workshop information, for example, describes it for a heated wideband (air/fuel ratio) sensor. A classic narrowband sensor produces its own small voltage and normally has no such line, but the code definition itself is generic, so check which sensor your engine has.
- What do bank 1 and sensor 1 mean?
- Bank 1 is the side of the engine that holds cylinder 1, and on a four-cylinder engine there is only one bank. Sensor 1 is the sensor before the catalytic converter, the upstream one. On a V or boxer engine the other side is bank 2.
- Can I drive with P2243?
- Yes for a short time, but not for weeks. Without that sensor's feedback the computer cannot trim the mixture precisely, which can raise fuel use and emissions. Fix it soon and stop sooner if the engine runs rough or loses power.
- Is P2243 the same as P0134?
- No. P0134 says the sensor shows no activity at all. P2243 says the reference voltage circuit that feeds and reads the sensor is open. A broken wire can cause both, so they can appear together.
- Should I replace the oxygen sensor straight away?
- Check the fuse, connector and harness first. A damaged wire or a loose plug gives the same code, and a new wideband sensor costs more than a repair to the wiring. Replace the sensor when the wiring tests good or the reference voltage is present but the sensor still fails.
Read our detailed guides
Sources
- saabwisonline.com saabwisonline.com/9-5-9650/2010/2-engine/engine-management-and-fuel-system-4-cyl
- saabwisonline.com saabwisonline.com/9-5-9650/2010/2-engine/engine-management-and-fuel-system-4-cyl
- mazdas247.com mazdas247.com/forum/goto/post?id=6525544