P045B: low-pressure EGR position tracking outside tolerance

P045B compares requested and measured low-pressure EGR position in this implementation. Its failure criterion is an absolute tracking error greater than 10%, intended to identify obstruction during opening or closing.

Stability requirements matter

The continuation requires setpoint change between −50 and 50% per second for at least 0.35 second. Position control must be closed loop, with no mechanical-stop soft approach or anti-sticking procedure underway. A mismatch recorded during one of those special movements is not automatically an eligible failure sample.

The monitor also requires valid temperature information, outside air at least −20°C, coolant at least 40°C or the cooling-system target reached, supply above 11 V, no cranking and cold-start strategy inactive.

Keep the electrical branch open

The filter uses 960 failures among 1,200 samples on a 6.25 ms task. At 480 failed counts it enables the P045A open-circuit check. That second result can change the interpretation of apparent obstruction by adding evidence of missing electrical loading.

Verification should show valid feedback following a sufficiently stable request under enabled conditions. The source does not prove a particular deposit pattern or prescribe cleaning. Diagnose the tracking error together with any open-load evidence and the exact service procedure before deciding whether a mechanical or electrical repair is warranted.

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 1190; gm-2025-04b, PDF page 1191.