Knowledge Base
Last Updated: 2026-07-02
NRC 0x31 usually means the ECU received a service request whose parameters or preconditions did not fit the allowed range.
The request can fail because the parameter block is malformed, a coding precondition is missing, or the selected data identifier is not valid for the ECU state.
In OEM workflows this often appears during coding or calibration operations when the operator only sees a tool-level error and not the exact request payload.
Look for the service identifier that immediately precedes the 0x7F negative response and confirm whether the failing sub-function or parameter block was sent correctly.
The important part is not just spotting NRC 31, but reconstructing the request chain that made the ECU reject it.
Was the ECU already in the right diagnostic session, security level, or environmental condition before the rejected request was sent?
Did the tool send the wrong data identifier, sub-function, or payload length even though the workshop symptom only showed a generic coding failure?
A structured timeline makes it easier to connect the negative response to the exact request packet, not just to the user-visible operation label in the diagnostic tool.
That matters when several writes, reads, or routine control calls happen close together during coding or flashing.
These examples are drawn from real capture files available in the project evidence pool. They give the article something stronger than generic protocol theory.
PAS flashing capture with a concrete 0x34 -> 0x31 reject
Evidence reference: EVID-NRC31-PAS-DOWNLOAD-01
Node roles in this case
A DoIP capture where the request chain narrows to a single RequestDownload rejection instead of a vague workshop symptom.
Evidence signals
Timeline
This is the kind of capture that lets the KB explain that NRC 31 is rarely useful in isolation. The preceding request chain is the actual evidence.
A compact routine-control style request is rejected directly with NRC 0x31
Evidence reference: EVID-NRC31-ROUTINE-ADC-01
Node roles in this case
A short v2 DoIP capture where the useful teaching value comes from how little ambiguity is left in the final rejection window.
Evidence signals
Timeline
This gives the KB a second NRC 31 pattern: not a long precondition chain, but a short direct reject that is easier for readers to recognize in the wild.
These are the interpretation traps that real packet evidence helps avoid.
Use nearby guides to move from protocol filtering to root-cause troubleshooting without leaving the knowledge base.
It means the ECU rejected the request because the parameter set, sub-function, data identifier, or precondition fell outside the accepted range.
Trace the 0x7F negative response backward to the immediately preceding service and inspect the exact request payload, not just the tool label.
Best when coding or calibration fails but the diagnostic tool hides the exact rejected payload.
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