Diagnostic article Generic OBD-II
P0385: Missing low-resolution crank pulses despite other timing signals
P0385 detects absent low-resolution crank information while other timing references show engine movement.
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Documented application
2009 General Motors diagnostic parameter file 09OBDG09 Engine Diagnostics.pdf. Section-specific modules and calibrations; no per-code model or engine applicability established.
The code alone does not identify a failed part or establish that a vehicle is safe to drive. Confirm the vehicle, reporting module and applicable service procedure.
In this GM group 09 implementation, P0385 concerns the low-resolution crankshaft signal identified as sensor B. The controller compares that signal with medium-resolution crank pulses and a camshaft reference. The code therefore describes missing information in a multi-signal timing system, not merely an engine that is stationary.
Other pulses establish the expectation
The failure description requires medium-resolution and cam evidence while the low-resolution pulse count remains zero. That relationship explains why checking each signal independently may overlook the actual diagnostic question: did the expected low-resolution events accompany the other timing events?
The listed prerequisites include engine running time and engine-speed information. The monitor accumulates 40 failures in 50 samples, with evaluation tied to the relevant signal interrupts and the cam check. This is a recognized pattern of missing pulses rather than one instantaneous observation.
Keep absence separate from an incorrect count
The neighboring P0386 strategy addresses a low-resolution count that is present but inconsistent. That distinction can guide whether the service procedure investigates complete signal loss or waveform/pattern plausibility.
Preserve companion timing codes and the available synchronization record. The summary does not establish a sensor location, connector pin or automatic replacement decision. After work, verify that the expected timing signals are consistently recognized together and that the applicable monitor completes. A single successful start does not demonstrate correction of an intermittent missing-signal condition.
Source and applicability
2009 General Motors diagnostic parameter file 09OBDG09 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.
Article source documents
Source checks describe how the text was prepared; they do not certify a diagnosis or confirm compatibility with every vehicle using this code.
Original code reference
Dictionary definition
Crankshaft Position Sensor B Circuit
This definition retains its original catalog scope. The article above is limited to its explicitly documented application.
Reference scope
Generic OBD-II definition.
A manufacturer label does not establish the model, year, engine or module to which a diagnosis applies. Read the safety and diagnostic limits.
Definition source
- DTC Database: pinned community code definitions
Source checked · MIT