Diagnostic Trouble Code - Status Byte

• A Diagnostic Trouble Code (DTC) is linked to an event, changing status when the event is reported as passed or failed.
• The DCM uses the DTC number to read information about diagnostic events and services, such as 19 02 or 19 04 or 19 06.
• The monitor function (runnable entity) in the SWC tracks events and reports their status to the DEM module via an RTE call, influencing the DTC status.
• According to the UDS (ISO 14229) protocol, DTC status is stored in a byte known as the DTC status byte.
• The DEM module maintains a DTC status byte for each diagnostic event, with each DTC number being 3 bytes (UDS) and 2 bytes (OBD).

DTC Status Byte

1.????? Bit 0 – Test Fail

Shows that the DTC failed at the time of DTC request/ most recently performed test. Logic ‘1’ – DTC Mature / Active. Logic ‘0’ – DTC De-mature.

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2.????? Bit 1 – Test Failed This Operation Cycle

Shows whether the test failed anytime during the current operation cycle. This bit can be reset when the operation cycle is re-initialized or when $ 14 service is called.

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3.????? Bit 2 – Pending DTC

This bit reports that the test has failed anytime during the current operation cycle or last completed OC. This bit will not be cleared until the $14 service is invoked or an OC where the test has passed at least once without failing.

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4.????? Bit 3 – Confirmed DTC

This bit indicates whether the Fault is detected enough times so the DTC should be stored in long term memory (NVM). This bit doesn’t always indicate that the fault occurred at the time of request. To clear this bit either invoke $ 14 service or the aging threshold should be crossed.

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5.????? Bit 4 – Test Not Completed Since Last Clear

This bit indicates whether the test has been run to completion since last time $ 14. This bit indicates whether the test has been run to completion since last time $ 14 service was invoked. To reset either $ 14 service or test should complete with either pass/fail.

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6.????? Bit 5 – Test Failed Since Last Clear

Indicates whether the test has run to completion with fail status since last time $ 14 service was invoked. To reset aging threshold should be reached or fault memory should overflow.

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7.????? Bit 6 – Test Not Completed This Operation Cycle

Indicates whether the test has been run to completion during the current operation cycle. This bit can be reset when the operation cycle is re-initialized or when $ 14 service is called.

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8.????? Bit 7 – Warning Indicator Request

Reports any warning indicator related to the DTC. If no WI exist for a particular DTC then this bit will remain logic ’0’ as the server is not requesting. Conditions for activation of this bit is Vehicle Manufacture specific. If this bit is logic ‘1’ then Confirm DTC bit will also be logic ‘1’. To reset this bit either $ 14 service or Healing should happen.