P02D2: cylinder 4 minimum injector-learning authority

For the documented diesel monitor, P02D2 identifies cylinder 4's SQP adjustment falling below the permitted minimum. SQP learns injector energizing time from the pressure drop associated with a small commanded fuel quantity.

The lower limit belongs to a time correction

The relevant calibration is a minimum adapted time delta, expressed in microseconds. Neither low rail pressure nor low injector supply voltage is the quantity compared by this row. Those different interpretations would send diagnosis toward a test the monitor itself does not describe.

Learning occurs during diesel fuel cut-off and is evaluated as new values enter the map. The enabling information requires SQP authority diagnosis and injection management. Without an eligible update, absence of a new failure does not demonstrate recovery.

Look across the pressure map

The monitor maintains a saturation flag for each defined SQP rail-pressure level. One flagged entry can set the diagnosis; the described unset logic needs every flag clear. That makes the distribution of learned values useful evidence: an isolated pressure region and a broad pattern should not be collapsed into a single undifferentiated “bad injector” conclusion.

Use the vehicle's actual learned data and calibration limits to assess the result. The table provides Type B reporting over two trips and no part-replacement directive. Verification must show an appropriate learning result, and any physical fuel-system testing requires suitable professional procedures.

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 1149.