|Download Help (Windows Only)|
KWP2000 expects a diagnostic session to be started with StartDiagnosticSession and terminated with StopDiagnosticSession. However, StartDiagnosticSession has a DiagnosticMode parameter that determines the diagnostic session type. Depending on this type, the ECU may or may not support other diagnostic services, or operate in a restricted mode where not all ECU functions are available. The DiagnosticMode parameter values are manufacturer specific and not defined in the standard.
For a diagnostic session to remain active, it must execute the TesterPresent service periodically if no other service is executed. If the TesterPresent service is missing for a certain period of time, the diagnostic session is terminated, and the ECU returns to normal operation mode.