Difference between K-line and L-line bus protocols
This page compares K-line vs L-line protocols and mentions similarities and difference between K-line and L-line signal and its interface details.
Introduction : K-line and L-line are protocols used for communication between devices in automotive domain for various purposes such as diagnostics and control. K-line protocol is defined in ISO-9141 and it is a single wire serial communication protocol. It allows bidirectional communication between a diagnostic tool and various ECUs (Electronic Control Units) within the vehicle. ISO-9141 standard specifies electrical characteristics, signal encoding, timing and frame structure. L-line protocol is also single wire communication protocol used in automotive domain. L-line protocol specifications are defined in ISO 9141-2 or ISO 14230-2.
Following points summarize similarities between K-line and L-line protocols.
➨Both K-line and L-line support similar data rates i.e. 10.4 kbps (Kilobits per second).
➨Both K-line and L-line use similar signal voltage levels i.e. Logic-1 (0V to 4V) and Logic-0 (7V to 12V).
➨Both support half-duplex communication.
Note : Signal voltage levels and data rates may vary depending upon specific implementation, ECU and vehicle manufacturer.
Following points summarize difference between K-line and L-line protocols.
➨K-line is used as communication medium through OBD-II where as L-line signal is used for bus initialization.
➨K-line is interfaced to pin no.7 where as L-line is interfaced to pin no. 15 of OBD-II port.
➨L-line is used in conjunction with K-line for extended diagnostic capabilities. Refer advantages and disadvantages of K-line protocol >>.