P046C: EGR position differs from the commanded target

P046C is a performance check of EGR position in this GM Duramax summary. The controller compares desired valve position with the reported actual position while EGR control is active. A sensor voltage can remain within its electrical range while the commanded position is not achieved.

Duration and command state matter

The table describes a deviation of approximately three percentage points in either direction, persisting for five seconds. The relevant evidence is therefore a target-and-response comparison over time. One actual-position reading without the target does not establish whether the controller considered the valve incorrect.

This strategy differs from the neighboring P0405 and P0406 low- and high-voltage checks. An in-range performance error should not be treated as an extreme circuit signal simply because both involve the position sensor.

Review inhibiting faults before judging completion

Specified EGR flow, control-circuit and reference-voltage faults prevent this monitor from making its normal judgment. If one remains active, the absence of a returning P046C can mean that the comparison did not run.

Preserve desired position, actual position, active-control status and related faults. The summary does not distinguish a biased position signal from an actuator or physical-response problem on the code alone. Follow the exact engine's diagnostic procedure to separate those possibilities. Verification should demonstrate credible target tracking and completed performance monitoring after relevant prerequisites are restored, rather than only a cleared memory or a stationary valve position.

Source and applicability

2009 General Motors diagnostic parameter file 09OBDG01 DURAMAX Engine Diagnostics.pdf. Section-specific modules and calibrations; no per-code model or engine applicability established. This explanation describes the documented monitor, not a universal repair procedure.

GM diagnostic parameters, PDF page 13.