Diagnostic article Generic OBD-II
P0393: bank-2 exhaust camshaft signal lost at high level
P0393 monitors the bank-2 exhaust camshaft signal for a high-level no-signal condition.
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Documented application
2025 GM 25OBDG07A Part2 diagnostic monitor documentation; the application-matrix filename mismatch is unresolved, so no model or engine applicability is inferred.
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.
P0393 monitors the bank-2 exhaust camshaft signal for a high-level no-signal condition. The controller detects that expected new edges have stopped while the input remains permanently high.
The crankshaft provides the observation interval
The documented criterion uses at least four crankshaft revolutions. Ignition must be on, the crankshaft signal’s reference gap must be detected, and backward engine rotation must not be detected. These prerequisites distinguish a qualified missing-cam-signal event from an arbitrary static reading.
The time required to complete four revolutions depends on engine speed. A fixed-duration recording can therefore contain enough evidence at one speed but too little at another. Retaining revolution or synchronization context improves interpretation.
Verification and channel identity
The source explicitly names the outlet camshaft on bank 2. The neighboring low-state and rationality codes examine different failure signatures, so a circuit-high result should not be rewritten as a generic timing-correlation fault.
One-trip reporting is listed. Verification should show sustained, correctly attributed bank-2 exhaust-cam edges while the crankshaft reference remains valid and the monitor is enabled. The presence of the code does not prove a particular electrical short or a mechanical timing problem; those causes require the applicable circuit and signal tests.
Documentation and applicability
These details describe the monitor in GM’s 2025 25OBDG07A Part2 file. Its application-matrix filename does not match the download index, so model and engine applicability remain unresolved. Use the vehicle’s correct service information before applying these calibration details.
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
Camshaft Position Sensor B Circuit High Bank 2
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