P24B1: particulate sensor electrode signal shorted to power

P24B1 is an electrical high diagnosis for the particulate-matter sensor electrode signal. The sensor control unit compares the ADC voltage used for electrode-current measurement with 4.1 V. A value above that boundary is described as a short-to-power indication.

Sensor-unit and ECM roles differ

The table lists no additional conditions inside the sensor control unit, but ECM reporting requires the bus relay on, no relay fault, valid communication and no sensor-control-unit undervoltage fault. A temperature qualification and hysteresis also apply. These are separate layers: detecting an internal electrical condition and accepting it for vehicle-level reporting.

The counter is either 24 consecutive failures or 24 failures out of 92 samples at 100 ms intervals. Reporting is Type B, two trips.

Interpreting a high value

This is the electrode-current measurement voltage, not an exhaust soot-concentration threshold. A high particulate reading cannot substitute for the electrical measurement, and an ordinary external supply measurement may be a different signal entirely.

Use the exact service data to identify supported internal status and circuit tests. Verify valid supply and communication alongside completion of the electrode-high check. The threshold does not establish a specific terminal location or prove that a particular harness section, control unit or sensing element must be replaced.

Source and application limits

This explanation covers the cited 2025 GM monitor. Confirm the vehicle and calibration in its service information before applying these limits; inclusion in this file does not establish model compatibility. GM diagnostic parameters, PDF page 1493.