UDS Protocol Interview Question

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UDS Protocol Interview Question 


Functional Group in UDS

  • Diagnostic and communicatio management
  • Data Transmission
  • Stored Data Transmission
  • Input/Output Control
  • Remote Activation of Rountine
  • Upload / Download
Total (27 )services untill 2020,As Per ISO 14229 2020 there are (28) services.

Why it is called UDS

  • Unified      - Term 'Unified' in this context mens  that it is an international and not a Company- Specific Standard
  • Diagnostic - Finding Root cause
  • Service      - checking with existing content

What are the types of request in UDS

  • Valid request 
  • Invalid request

What are types for Responce in UDS.

  • Positive responce
  • Negative Responce

What are type of NRC

  • ISO Specific (0x12,0x13,0x22)

  • ISO Reserved or Manufacture Specific (0x32,0x84 etc)
What are the commonly used NRC

  • 0x12
  • 0x13
  • 0x22
  • 0x24
  • 0x33

In Default which session will be active

  • UDS supports different Operating session, which can be changed using the "Diagnostic Session control".
  • Depending on which session is active,diffrent services are available. 
  • On Start, the control unit is by default in the Default session

What are the sub functions in Diagnostic Session control and explain each ?

There are 3 standard sub-fuctions in UDS. 
  • "Default session" used in standard Operation mode
  • "Programming session" used to upload/Download the software.
  • "Extended Diagonstic Session" Used to unlock additional diagonstic fucntions,such as the adjustment of senors and actuators.

After Programming session is possible to move to extended session or any non-diagnostic session ? justify your answer 

  • No its not possible to jump. once progamming session is completed , we have to move to default session.

When is security access is used and explain its algorithm ?

Security access is used to get "unlock permission" to do some specific special operation that to be in special sub function such as "Extended session control"

What do you know about NRC22?

send by ECU: NRC 22 is used to indicated the negative condition in different invalid environment or invalid request from tester

What is the difference between ECU reset service and remaing services?

The ECU reset Positive responce message(if required) shall be sent before the reset is executed in server(s) reamaning services after reacting they will give response. 

What response will come after successfulll unlock of security if again requested seed.

  • Security level is already unlocked when a security access"Request seed " message is received , that server shall respond with a security access "Request seed " postive responce message service with a seed value equal to zero(0)

*When Clear diagnstic session sends NRC 12

  • No, because it doesn't contain any sub functions

If no DTC is described in the DTC list matches the requested DTC which NRC ecu will respond. 

  • NRC 0x31

Explain the status bit of DTC

  • 0 --> Test failed
  • 1 --> Test Failed this operation cycle
  • 2 --> Reserved DTC
  • 3 --> Confirmed DTC
  • 4 --> Test not complete since last clear 
  • 5 --> Test Failed since last clear
  • 6 --> Test not completed this operation cycle
  • 7 --> Warning indictor requested

In communication control service while giving the inputs what communication type indicates

  • Normal Communication Messages.
  • Network Management commjnication Messagees. 
  • Normal & Network Management comminiction Messages.

What are permanent DTC?

  • Permanent DTCs shall eb stored in non-volatile Memory. there DTC can't be cleared by any test equipment. 
  • Permanent DTCs shall be erasable if the engine control module is reprogrammed and the readiness status for all the monitored comonents are systems are set to "not complete"



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