P2493: EGR bypass tracking depends on completed offset learning

P2493 is an EGR cooler-bypass performance diagnosis in this GM diesel table. The controller evaluates deviation between the requested and actual actuator value. It does not treat every unfavorable position reading as the same electrical fault.

Learning status changes what the comparison means

The documented deviation limits are greater than positive 10 percent or less than negative 10 percent. The fault must persist for eight seconds. Evaluation requires the actuator to be active, offset learning to be inactive at that moment, and the previous driving cycle's offset learning to have completed.

Those prerequisites matter after component or programming work. A comparison made without the required learned reference cannot simply be interpreted as the completed performance test described here. Preserve the learning status together with desired and actual values rather than presenting one position percentage alone.

Distinguish tracking from a signal outside its electrical range

The same page describes separate low- and high-voltage position-sensor faults. Their electrical thresholds answer a different question from P2493's actuator-tracking deviation. Related circuit faults and their effect on monitor eligibility must be considered before concluding that the valve is mechanically stuck.

The table also requires coolant temperature and engine operation to meet its enabling conditions. It does not supply a universal bypass-valve cleaning instruction or a replacement rule. Use the exact engine's procedure to establish the cause, then verify that a properly learned, enabled actuator can follow the requested value without the original deviation recurring.

Source and applicability

GM 2015 15OBDG09 LML/LGH-common EGR cooler-bypass monitor. Only the cited monitor and calibration are described; per-code vehicle and engine applicability has not been established.

15OBDG09 Engine Diagnostics, physical PDF page 223.