Understanding how the ECM manages torque and driver demand in an LML Duramax is crucial for diagnostics and tuning. While logging and tuning these engines, several questions arise regarding the interpretation of various torque and injection related PIDs available through a Duramax Pulse Scan Tool. Let’s delve into some of these complexities.
One of the primary challenges lies in deciphering the various torque PIDs. A Duramax pulse scan tool will typically display parameters like “delivered torque to transmission,” “driver demanded engine torque,” “engine actual steady torque,” “actual engine percent torque,” and “driver demanded engine percent torque.” While these values often align logically, discrepancies can occur. For instance, at wide open throttle, the actual torque values don’t always match the commanded values in the pedal-to-torque map. Further clarification on the precise meaning and calculation of each PID would be beneficial for accurate analysis. A critical missing piece is the lack of PIDs directly correlating to the pedal-to-torque map, making it difficult to pinpoint the specific cell the ECM is referencing.
Another significant hurdle is the absence of a traditional main injection pulse width (uS) PID, a standard feature in previous diesel engines. While estimating injection duration based on rail pressure and commanded fuel quantity (mm3) is possible, relying solely on these parameters feels insufficient. The concern stems from the potential for the ECM to implement undisclosed adjustments behind the scenes. This uncertainty raises doubts about accurately determining the actual fuel injected into the engine. The available “injection time all” PID hasn’t proven entirely reliable due to inconsistencies with the main injection pulse table (B0552). This ambiguity further complicates precise fuel delivery analysis.
Adding to the complexity are the two distinct mm3 PIDs: “calculated fuel rate” and “injection quantity all.” While “calculated fuel rate” serves as a reliable reference, the purpose and interpretation of “injection quantity all” remain unclear. Understanding the nuances between these two PIDs is essential for comprehensive fuel system analysis.
Finally, the accuracy of existing scan tool link files for LML engines is questionable. Many tables appear incorrectly linked, hindering the seamless interpretation of data. An updated and accurate LML scan tool link file would significantly improve the diagnostic and tuning process. This updated file would allow for more precise correlation between the data displayed by a Duramax pulse scan tool and the actual engine operating parameters.
In conclusion, accurately interpreting the data provided by a Duramax pulse scan tool requires a deeper understanding of the LML’s torque and injection PIDs. Addressing the ambiguities surrounding these parameters, particularly regarding torque calculations, main injection pulse width, and the various mm3 PIDs, is crucial for effective diagnostics and tuning. An updated scan tool link file would greatly enhance the usability and accuracy of these tools for working with LML Duramax engines.
