Powertrain, generic (extended)

P2238 O2 Sensor Positive Current Control Circuit Low (Bank 1 Sensor 1)

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P2238 is the low-side fault of the pump-current circuit of the front wide-band sensor on bank 1. Saab's 9-5 2.0 turbo (2010) shows a concrete test: on overrun with the injectors shut off, pure air should drive the signal well above its stoichiometric level, and if it stays below 1.7 V for 3 s the code sets as Type B. GM's 2005 V6 tables use the same fuel-cut check but book it under P2237. Mitsubishi's 2022 Outlander lists P2238 as a two-trip code. Ford does not use it at all: a pump-current wire shorted to ground lands in P0131 there. P2237 is the open circuit, P2239 the high-side fault, P2241 the same on bank 2. Typical findings are a grounded IP wire or a sensor that can no longer pump oxygen.

Likely causes

Pump-current wire chafed through to ground
Aged or contaminated sensor that no longer reads lean in fuel cut-off
Fault in the sensor interface of the ECM

Symptoms

  • Check engine light after two drives
  • Lambda value does not rise during coasting in live data

Repair estimate

DifficultyMediumDIY possible
Parts and labour€80–400
Time0.5–2 h

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

Parts involved

oxygen sensor bank1 sensor1oxygen sensor wiringecm

Related codes

P2237P2239P2241P0131

References: saabwisonline.com, gsi.ext.gm.com, static.nhtsa.gov, newtonnet.co.uk.