Powertrain, generic (extended)

P2249 O2 Sensor Reference Voltage Circuit Low (Bank 2 Sensor 1)

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P2249 indicates that the reference voltage circuit of the front air-fuel sensor on bank 2 is pulled too low, most often by a grounded wire in the harness or a fault inside the sensor. The only public manufacturer criteria come from GM's tables for the Saturn Vue 3.5 V6 (L66, 2004-05), a Honda-built engine: after more than 85 s of running with the sensor heater active and the element signal at 3.2-4.6 V, a pump-cell circuit voltage under 1.5 V for half a second stores the code and lights the MIL in that drive cycle. The same table uses P2245 for bank 1. Ford, VW and GM's Bosch-equipped V6 tables do not list P2249. CARB requires circuit faults of fuel-control sensors to be detected. P2247 is the open line, P2250 high, P2255 the low fault of the ground line.

Likely causes

Reference voltage wire shorted to ground on the bank 2 sensor harness
Internal short in the bank 2 air-fuel sensor
Fault in the sensor interface of the ECM

Symptoms

  • Check engine light
  • Higher fuel consumption from open-loop fuelling on bank 2
  • Possible failed emissions test

Repair estimate

DifficultyMediumDIY possible
Parts and labour€80–450
Time0.5–2 h

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

Parts involved

oxygen sensor bank2 sensor1oxygen sensor wiringecm

Related codes

P2245P2247P2248P2250P2241P0151

References: gsi.ext.gm.com, gsi.ext.gm.com, law.cornell.edu.