P0337: Crank position found and then lost during a drive cycle

The generic P0337 description refers to a low crankshaft-position circuit. In GM's 2009 group 05 summary, the diagnostic description focuses on position being found and then lost twice in the same driving cycle. That is more specific evidence than simply seeing zero engine speed after the engine has stopped.

Loss after recognition is the important sequence

A controller that never recognizes position and one that recognizes it before repeatedly losing it have different diagnostic histories. Preserve that sequence when reviewing a no-start, interruption or intermittent running complaint. The code alone does not establish which physical component interrupted recognition.

The source places this check beside a separate crank-sensor activity and cranking-output strategy. Combining those rows into one assumed voltage test would erase the distinction between initial signal recognition and subsequent loss.

Use the exact implementation

The table does not provide a clear universal low-voltage threshold for P0337. Its behavior-based description differs from the broad generic label, so calibration confirmation remains necessary before applying an electrical pass/fail value.

Relevant evidence includes whether crank position was first acquired, when synchronization was lost, and what other position-sensor faults accompanied the event. Use vehicle-specific service information to evaluate the signal safely. A successful restart alone cannot prove that a repeated-loss condition is corrected; verify the applicable monitor and the original operating circumstances without assuming a sensor replacement is automatically required.

Source and applicability

2009 General Motors diagnostic parameter file 09OBDG05 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 10.