P2235: A bank 2 rear oxygen-sensor fault linked to heater switching

P2235 identifies signal-to-heater coupling for bank 2 oxygen sensor 2. In the GM monitor, the controller watches for an abrupt voltage change around heater shutdown. The test is about a relationship between two electrical functions, not ordinary mixture switching alone.

The heater-off event defines the comparison

The source lists a present-minus-previous voltage criterion above approximately 2.002 V and an observation window shorter than 40 milliseconds. The failure decision is associated with four events. These details make timing essential: a voltage screenshot taken seconds later cannot show whether the diagnostic condition occurred.

The row continues on the next page, where the operating-readiness requirement is explicitly assigned to bank 2 sensor 2. Using bank 1 readiness information would omit the affected sensor's actual eligibility.

What evidence helps locate the problem

Dew-point completion, the heater-off state and the applicable enable conditions qualify the test. Absence of another code while those conditions are unmet is not a passed coupling check.

A useful capture places heater transitions and rear-sensor signal changes on the same timeline at adequate resolution. Ordinary slow scan updates may hide a brief event. The code supports investigating an unwanted electrical relationship but does not prove whether it lies inside the sensor or elsewhere in the circuit. Vehicle-specific wiring information and test procedures are needed before selecting a repair; the source does not supply a universal probing point or component replacement instruction.

Source and scope

2025 GM 25OBDG07A Part 2 monitor tables only; model, engine and transmission applicability are not established by the unresolved application-matrix filename join. These are documented monitor criteria, not a universal repair procedure. GM PDF, physical page 512 · GM PDF, physical page 513.