Diagnostic article Generic OBD-II
P2238: the pump-circuit check uses missing lean response during fuel shutoff
In this GM calibration, P2238 evaluates upstream air/fuel sensor response after fuel shutoff, with the heater operating and the engine-start phase complete.
Read before applying this article
Documented application
GM 2009 09OBDG04 Engine Diagnostics, cited bank-one air/fuel pump-circuit response during fuel shutoff monitor only. Document-level evidence does not establish per-code vehicle, engine or wiring applicability.
The code alone does not identify a failed part or establish that a vehicle is safe to drive. Confirm the vehicle, reporting module and applicable service procedure.
P2238 has a general positive-current circuit-low description, but this GM 2009 row implements a pumping-current circuit check through sensor behavior during fuel shutoff. It asks whether the bank-one upstream air/fuel sensor becomes lean enough under that particular condition.
Fuel shutoff supplies the diagnostic context
The source uses an air/fuel sensor voltage below 1.7 V after more than three seconds of fuel shutoff. The engine must be running, starting must be complete and the sensor heater must be at operating temperature. Battery voltage is also restricted to the documented range.
That is not an ordinary idle-voltage test. A reading collected while fuel is being delivered, or before the sensor is heated, does not recreate the condition used by this monitor. The table assigns its own observation and persistence timing to the qualified event.
Do not apply a generic oxygen-sensor voltage rule
Preserve fuel-cut state, elapsed time and the actual air/fuel sensor channel with the reading. The source's sensor technology and calibration matter; a voltage rule for a different oxygen-sensor type cannot be substituted without the correct vehicle information.
The monitor does not prove which part of the pumping-current circuit is defective. It also does not prescribe sensor replacement from the code alone. Use the applicable circuit and response-test procedure to establish the cause. The parameter table supplies no road-test instruction or safe live-probing method, and physical sensor work requires appropriate electrical and exhaust-heat precautions.
Source and applicability
GM 2009 09OBDG04 Engine Diagnostics, cited bank-one air/fuel pump-circuit response during fuel shutoff monitor only. Document-level evidence does not establish per-code vehicle, engine or wiring applicability.
Article source documents
Source checks describe how the text was prepared; they do not certify a diagnosis or confirm compatibility with every vehicle using this code.
Original code reference
Dictionary definition
O2 Sensor Positive Current Control Circuit Low Bank 1 Sensor 1
This definition retains its original catalog scope. The article above is limited to its explicitly documented application.
Reference scope
Generic OBD-II definition.
A manufacturer label does not establish the model, year, engine or module to which a diagnosis applies. Read the safety and diagnostic limits.
Definition source
- DTC Database: pinned community code definitions
Source checked · MIT