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Negative Response Codes (NRCs)

When a request fails, the ECU returns a negative response frame:

7F <requestSID> <NRC>

Common examples:

  • 0x11 serviceNotSupported
  • 0x22 conditionsNotCorrect
  • 0x31 requestOutOfRange
  • 0x78 requestCorrectlyReceivedResponsePending (RCRRP)

How to handle NRCs

  1. Identify the request SID.
  2. Look up the NRC meaning.
  3. Fix session/security/sequence issues.
  4. Retry if appropriate.

RCRRP (0x78)

The ECU accepted your request but needs more time. Keep waiting and retry the request or wait for the final response.

pyudskit provides:

  • uds.explain_nrc("0x22")
  • uds.lookup_nrc(0x78)
  • Full NRC registry in pyudskit.registry.nrc