Diagnostic article Generic OBD-II
P064C: Glow-plug controller performance can include supply problems
P064C reports a diagnostic result from the glow-plug controller and does not prove an internal module failure.
Read before applying this article
Documented application
2009 General Motors diagnostic parameter file 09OBDG01 DURAMAX 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.
P064C reaches the engine controller as a diagnostic message from the glow-plug control module in this GM Duramax system. The underlying diagnosis takes place in the glow-plug controller. The engine controller's code is therefore a report of that result, not an independent component-level verdict.
Several fault classes can produce the report
The source includes glow-plug switching faults, missing ignition supply, excessive temperature, supply-voltage problems and internal memory failures. It also considers disagreement between battery voltages measured by different controllers. Those are materially different investigations; the module's name in the code does not justify immediate replacement.
A supply or measurement disagreement can produce a performance report even when the issue is not a failed memory device. Accessing the originating controller's detailed information is consequently more informative than working from the engine-controller label alone.
Confirm the originating evidence
The published engine-controller evaluation requires the reported condition for three seconds, with checks every 250 milliseconds and ignition on. Preserve the associated glow-plug-controller faults and supply information before clearing either module.
The summary refers to a separate controller table for detailed thresholds, so it does not support a universal voltage or part-replacement rule here. Verification should confirm that the originating condition is resolved and that communication and monitoring complete normally. An engine controller with an empty code list immediately after clearing does not establish that the glow-plug controller has passed its own checks.
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.
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
Glow Plug Control Module 1
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