Diagnostic article Generic OBD-II
P2C64: third oxygen channel above its physical-range limit
P2C64 detects an implausibly high oxygen measurement from the third sensor channel in the documented monitor.
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Documented application
Documented 2025 GM gm-2025-04b monitor only; vehicle, engine and controller applicability must be established separately.
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.
P2C64 is described generically as oxygen-sensor pumping-current trim circuit high. In this GM table, the actual strategy rejects an oxygen signal above its physical maximum, with a documented threshold greater than 29.00%. The input is associated with the third NOx sensor's oxygen measurement.
What “high” applies to
The high limit applies to the reported oxygen concentration channel, not directly to exhaust pressure, sensor heater temperature or a universal connector voltage. The strategy wording says physical maximum even though another table column contains an apparent “minimum” label. The numerical upper comparison and strategy establish the supported interpretation.
The sensor must be fully operative and not flagged invalid. Engine operation, system voltage above 11 volts and an enabled combustion mode are also required. A failure decision needs 100 failing samples out of 200, evaluated at 25 milliseconds per sample.
Avoid confusing availability with range
Check whether the third oxygen channel was ready and valid when the unusually high value appeared. A default scan-tool number during sensor unavailability does not reproduce the same measurement test. Conversely, a sustained excessive reading with a valid interface is evidence that deserves a range-specific investigation.
Confirmation should show the qualified oxygen channel below its upper diagnostic bound while the monitor completes. Agreement with another oxygen channel may help interpretation, but this row itself is an absolute range check. It does not specify a wiring fault location or prove which internal sensor element caused the measurement error.
Source and applicability
Documented 2025 GM gm-2025-04b monitor only; vehicle, engine and controller applicability must be established separately. GM monitor table, PDF page 1536.
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 Pumping Current Trim Circuit High Bank 1 Sensor 3
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