DTC Status Definitions

  • DTC Pending - Condition has failed the test some times, but not enough to set a code. It needs more runtime/drive cycles.
  • DTC Confirmed - Condition has failed the test many times or all times.
  • DTC Stored - A confirmed DTC is saved to the ECM.
  • DTC Active - Fault is actively happening or instantly happens when power is given.
  • DTC Freeze Frame - A snapshot of what has happened during the DTC is saved for the mechanic.
  • DTC Inactive - Condition has failed the test in the past but is no longer failing the test.
  • DTC Permanent - Usually for emissions codes, requires a drive cycle or ECM reset to clear.
  • DTC Archived - Inactive DTC has remained inactive long enough to no longer be relevant.

Important Note

When a DTC is active, clearing the code most likely won’t solve it! Every time the ignition is power cycled, the ECM and CAN modules will perform a circuit test on all components. Any failed circuit tests will pop up immediately.

Secondary DTCs

When a DTC has a second code, because the first code happened, this is a secondary DTC. Like an O2 sensor code from an engine running lean, or a coolant low code from no coolant sensor detected.

Enhanced DTCs

Kind of like secondary DTCs, but a more simple fault (circuit code) was fixed and it let the PCM read the sensor properly to find another issue

ECM Failure

ECM Failure is very uncommon. Make sure to pinpoint test circuits on both sides and make sure any canbus modules are getting power and ground before installing a new module.

Terminology

FMI - Failure Mode Identifier SPN - Suspect Parameter Number MIL - Malfunction Indicator Lamp DTC - Diagnostic Trouble Code SPI - Serial Peripheral Interface PID - Parameter Identifier

Other info

  • There is a difference between changing parameters and reflashing ECU software. Examples below.
  • Forscan vs HPTuners
  • Techstream vs ECU reflash
  • Genlink vs Firmware Update S Record File
  • Parameters mess with lower level variables than ECU logic.