Powertrain, generic (extended)

P2243 O2 Sensor Reference Voltage Circuit/Open (Bank 1 Sensor 1)

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modeNo

P2243 flags an open reference voltage line on the front wide-band sensor of bank 1, i.e. the Nernst-cell lead (RE/UN on Bosch sensors, VS on NTK). Ford's OBD summaries set it on Bosch parts when the sensor voltage sits above 4.7 V or below 0.2 V for 10 s; on NTK parts the interface chip reports the break itself. GM's 2005 V6 tables and the 2010 Saab 9-5 2.0 turbo use the same voltage window with cell resistance above 570 ohms, as a two-trip Type B code. On the 2004-05 Saturn Vue 3.5 V6 the pump-cell voltage must swing both above 4.8 V and below 3.4 V fifty times. Honda bulletin 14-002 ties it on 2010-11 V6 models to a broken sensor tip, often with P0420/P0430; Ford reflashes the 2020 Explorer 2.3 (20-2217). P2247 is bank 2, P2245/P2246 low/high.

Likely causes

Broken reference voltage (Nernst cell) wire or pushed-back pin between sensor and ECM

Sensing element cracked or tip broken off, for example by thermal shock

Corroded or loose sensor connector

Engine software that sets the code falsely (update available for some models)

Symptoms

Check engine light
Higher fuel consumption from open-loop fuelling on bank 1
Catalyst efficiency code P0420 alongside it if a sensor fragment damaged the converter

Repair estimate

DifficultyMediumDIY possible

Parts and labour€0–450

Time0.3–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

oxygen sensor bank1 sensor1oxygen sensor wiringecm

References: newtonnet.co.uk, fordservicecontent.com, gsi.ext.gm.com, gsi.ext.gm.com.