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There shall be always exactly one diagnostic session active in the VU,
The VU shall always start the StandardDiagnosticSession when powered up. If no other diagnostic session is started, then the StandardDiagnosticSession shall be running as long as the VU is powered,
If a diagnostic session which is already running has been requested by the tester, then the VU shall send a positive response message,
Whenever the tester requests a new diagnostic session, the VU shall first send a StartDiagnosticSession positive response message before the new session becomes active in the VU. If the VU is not able to start the requested new diagnostic session, then it shall respond with a StartDiagnosticSession negative response message, and the current session shall continue.
| Table 14 | |||
| StartDiagnosticSession Request Message | |||
| Byte # | Parameter Name | Hex Value | Mnemonic |
|---|---|---|---|
| #1 | Format byte — physical addressing | 80 | FMT |
| #2 | Target address byte | EE | TGT |
| #3 | Source address byte | tt | SRC |
| #4 | Additional length byte | 02 | LEN |
| #5 | StartDiagnosticSession Request Service Id | 10 | STDS |
| #6 | diagnosticSession = [one value from Table 17] | xx | DS_… |
| #7 | Checksum | 00-FF | CS |
| Table 15 | |||
| StartDiagnosticSession Positive Response Message | |||
| Byte # | Parameter Name | Hex Value | Mnemonic |
|---|---|---|---|
| #1 | Format byte — physical addressing | 80 | FMT |
| #2 | Target address byte | tt | TGT |
| #3 | Source address byte | EE | SRC |
| #4 | Additional length byte | 02 | LEN |
| #5 | StartDiagnosticSession Positive Response Service Id | 50 | STDSPR |
| #6 | diagnosticSession = [same value as in byte #6 Table 14] | xx | DS_… |
| #7 | Checksum | 00-FF | CS |
| Table 16 | ||||
| StartDiagnosticSession Negative Response Message | ||||
| a – the value inserted in byte #6 of the request message is not supported, i.e. not in Table 17, | ||||
| b – the length of the message is wrong, | ||||
| c – the criteria for the request StartDiagnosticSession are not met. | ||||
| Byte # | Parameter Name | Hex Value | Mnemonic | |
|---|---|---|---|---|
| #1 | Format byte — physical addressing | 80 | FMT | |
| #2 | Target address byte | tt | TGT | |
| #3 | Source address byte | EE | SRC | |
| #4 | Additional length byte | 03 | LEN | |
| #5 | Negative Response Service Id | 7F | NR | |
| #6 | StartDiagnosticSession Request Service Id | 10 | STDS | |
| #7 | ResponseCode = | [subFunctionNotSupporteda | 12 | RC_SFNS |
| incorrectMessageLengthb | 13 | RC_IML | ||
| conditionsNotCorrectc | 22 | RC_CNC | ||
| #8 | Checksum | 00-FF | CS | |