Day-31 Understanding UDS Negative Response Codes (NRCs) in ISO 14229 | ECU Diagnostics Made Easy 🚫 скачать в хорошем качестве

Day-31 Understanding UDS Negative Response Codes (NRCs) in ISO 14229 | ECU Diagnostics Made Easy 🚫

In this session, we explore one of the most important parts of UDS diagnostics — Negative Response Codes (NRCs) as per ISO 14229. NRCs are used by the ECU to indicate error or rejection of a diagnostic request. 📘 Why Learn About NRCs? Understanding NRCs helps you quickly identify problems in communication, improve test scripts, and handle error conditions correctly during ECU diagnostics and testing. 🔹 What is a Negative Response Code (NRC)? When an ECU rejects or fails to process a diagnostic request, it responds with a Negative Response Message, which includes an NRC indicating the reason for failure. 🔹 NRC Message Format: 📌 Negative Response Format: 7F Service_ID NRC Example: Request: 22 F1 90 Negative Response: 7F 22 13 Meaning: Request 0x22 was rejected with NRC 0x13 (Invalid Format) 🔹 Commonly Used UDS NRCs (Negative Response Codes): NRC (Hex) Meaning Description 10 General Reject General failure without specific cause 11 Service Not Supported The requested service is not supported by the ECU 12 Sub-function Not Supported The requested sub-function is not available 13 Incorrect Message Length or Invalid Format Request format is wrong 14 Response Too Long ECU cannot process due to response size 21 Busy Repeat Request ECU is temporarily busy 22 Conditions Not Correct Current conditions do not permit this request 24 Request Sequence Error Incorrect sequence of diagnostic requests 25 No Response From Subnet Component A sub ECU/component didn’t respond 26 Failure Prevents Execution of Requested Action Internal failure 31 Request Out of Range Parameter or value is out of supported range 33 Security Access Denied Security access denied (wrong key or attempt failed) 35 Invalid Key The key provided is incorrect 36 Exceeded Number of Attempts Too many failed attempts – ECU is locked 37 Required Time Delay Not Expired Must wait before sending another security request 78 Response Pending ECU is processing – wait for positive response 7E Sub-function Not Supported in Active Session Allowed only in specific diagnostic session 7F Service Not Supported in Active Session Request rejected in the current session 81 RPM Too High Engine speed too high for request 83 Voltage Too High Vehicle voltage too high 84 Voltage Too Low Vehicle voltage too low 🔹 Real-Time Use Case Example: Request: 27 01 (Security Access Request for Seed) Response: 7F 27 37 ✅ Meaning: Required delay time has not yet expired. Request: 22 F1 90 (Read Software Version) Response: 7F 22 13 ✅ Meaning: Incorrect format or length in the request. 💡 When Do NRCs Occur? Sending invalid or unsupported requests Accessing functions without proper session/security Violating request sequences Failing to meet physical or environmental preconditions 🚀 Why This Matters: Understanding NRCs is vital for diagnostics engineers, testers, and developers using Vector CANoe, CAPL, or Python automation scripts. It helps ensure robust communication, proper error handling, and faster debugging in real vehicle or HIL environments. 📌 Summary: UDS NRCs are essential for reliable diagnostics. By mastering them, you improve your ability to interpret ECU feedback, build resilient diagnostic tools, and accelerate development cycles.