P223C: Oxygen pump current is implausible during fuel cutoff

P223C checks wide-range oxygen-sensor pump-current performance on bank 1 in the reviewed GM strategy. It evaluates the signal during deceleration fuel cutoff, when the operating state provides a defined context for identifying abnormal pump-current behavior.

Three separately counted failure regions

The source describes excessive positive current above 5 mA, a near-zero region between minus 0.30 and plus 0.30 mA, and negative current below minus 0.10 mA. Each region has its own counter. Any region reaching 128 failures in 160 samples can establish the fault; sampling occurs every 25 milliseconds.

These regions are specific diagnostic definitions, not a universal acceptable-current range for all engine operation. In particular, a current observed under normal fueling cannot be assessed as though the fuel-cutoff test were active.

Why the monitor may not run

The sensor interface must report valid measurements and ready status. Heater warm-up and the following circuit-diagnostic delay must be complete, and listed heater or bank-level faults must be absent. The test is further limited by calibrated minimum and maximum time in fuel cutoff.

The source says this strategy can detect opens affecting pump current, reference-cell voltage or reference ground. P223C therefore does not uniquely identify the pump-current wire despite its title.

For verification, establish that an eligible fuel-cutoff window occurred and that none of the independently counted regions failed. The table is a monitor description, not a safe instruction to reproduce deceleration conditions on public roads or to replace a sensor without circuit evidence.

Source and applicability

The documented system and calibration must be confirmed for the vehicle before using these limits. GM diagnostic table, PDF page 621.