P04D0: upstream low-pressure EGR temperature resistance too low

P04D0 monitors the upstream low-pressure EGR temperature sensor for a raw resistance below 7 ohms. The cited GM row describes this as an electrical out-of-range-low condition.

Resistance is the fault quantity

The code does not directly state that EGR gas is colder than expected. “Low” refers to the raw electrical resistance compared by this monitor. Converting the label into a temperature conclusion without the sensor's transfer characteristic would be unsupported.

The table requires the engine not to be cranking, relay voltage above 11 V and the diagnostic enabled by calibration. Its failure filter is 30 counts among 38 samples on a 100 ms function task, with Type A reporting after one trip.

Distinguish electrical range from plausibility

This test does not need the long soak or reference-temperature agreement used by P04CF. A low resistance event can therefore be assessed in a different operating context from a cold-start plausibility failure. The two codes answer different questions even when they concern the same named temperature channel.

For verification, establish an in-range raw signal during an eligible electrical assessment. A plausible converted temperature alone is weaker evidence if the raw signal or validity flag remains abnormal. The summary does not provide a wiring location, sensor specification across temperature or safe in-circuit meter procedure; use the exact vehicle's service information to isolate the fault.

Source and applicability

2025 GM 25OBDG04B diagnostic parameter tables; the cited monitor only. Vehicle, engine and calibration applicability must be confirmed separately. These tables describe detection logic, not a complete repair procedure or a component replacement verdict. gm-2025-04b, PDF page 1211.