Powertrain, generic (extended)

P232F O2 Sensor Out of Range During Deceleration (Bank 1 Sensor 2)

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modeNo

P232F checks the downstream oxygen signal of bank 1 while fuel is cut on deceleration and the exhaust holds almost pure air. GM uses it on the 2023 6.6L L5P Duramax (Silverado HD, Sierra HD): the O2 value of sensor 2, the downstream NOx sensor, is compared with that of sensor 1 once the latter is stable in overrun; if the filtered difference leaves the window of +3.01 % to −3.18 %, a Type B fault is stored. The test runs only while P2297 is being evaluated and after 30 g of air have passed since. CARB requires rear-sensor monitoring and, where a full check is not feasible, at least a rich-to-lean check during fuel shut-off. Ford tests its rear petrol sensor in overrun too but files results under P013A, P013E or P2270. Code lists give P239E the same title. Causes are a drifting sensor, an exhaust leak or wiring faults.

Likely causes

Downstream sensor drifting or aged (on GM diesels the O2 signal of NOx sensor 2)

Exhaust leak near the downstream sensor

Damaged sensor wiring or connector (chafing, corrosion)

Leaking injector or upstream sensor fault distorting the overrun comparison

Symptoms

Check engine light on
Usually no change in driving behaviour
MIL only after two trips with the fault (GM Type B)

Repair estimate

DifficultyEasyDIY possible

Parts and labour€0–300

Time0.3–1.5 h

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

Parts involved

oxygen sensor b1s2nox sensor downstreamexhaust after catalyst b1

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