Current / Stored / Active / Past / History Fault Codes Explained

Diagnostic Trouble Codes (DTCs) in professional diagnostic scanners provide detailed information about vehicle faults’ current and past states.

Here’s an explanation of the terminologies:

Stored and Current

Stored and Current: This usually indicates a fault detected in the past and is still present. It’s one of the most common code statutes. You will need to address the issue, and this code will change to STORED only, at which point you can clear it.

Current Fault Codes

Current faults (Active DTC) are codes that indicate problems that are present right now. The diagnostic system has detected an issue that is currently occurring. This code may not have been detected previously, and the car was most likely detected during this run cycle.

These codes will not clear until you fix the issue. If they do clear, they will surely return after a day or two of driving. Fix the problem, and the status of these codes will change from Current to Stored, at which point you can clear them.

Stored Fault codes

Stored / Past / History Faults: These are issues that have occurred previously but are not happening now. They give technicians an idea of intermittent problems or issues that might have been temporarily corrected but could return.

Event

This might not be a fault but an event that the ECU deemed important to log. For example, an “event” could be a sudden drop in oil pressure that was only momentary but might warrant investigation. The fault code may say Stored and Current (Event) or Stored (Event).

MIL ON / CEL ON

“MIL” stands for “Malfunction Indicator Lamp,” and “CEL” stands for “Check Engine Light.” Both terms refer to the same dashboard warning light in most vehicles, illuminating when the vehicle’s onboard diagnostic (OBD) system detects an issue.

When someone says “MIL on” or “CEL on”, the specific fault code has triggered or turned on the check engine light or the corresponding malfunction warning the instrument cluster.

When the MIL/CEL is on, Diagnostic Trouble Codes (DTCs) will be stored in the vehicle’s computer, which can be read with an OBD scanner to help diagnose the issue.

Can I clear stored and current codes?

When you hit “erase” on your YOUCANIC diagnostic tool, here’s what typically happens:

Current / Active Faults- These will be cleared from the active list, but if the underlying issue causing the fault hasn’t been resolved, the fault can return when you cycle the ignition back on. Think of this as turning off a check engine warning light because you have an EVAP leak; the light goes off, but if the problem persists, it’ll come back on.

Stored / Past / History Faults- These are cleared from the history, but again, if the root cause of the problem hasn’t been resolved, the fault could come back and be logged.

Event– Events, being more of a log than an actual fault, might not be clearable like traditional DTCs. The specifics depend on the vehicle’s diagnostic system and how it treats these events.

While you can “erase” or clear many fault codes from the diagnostic tool’s memory, the fault will likely return if the underlying issue causing the fault hasn’t been addressed. So, clearing a fault doesn’t fix the problem; it just resets the diagnostic system’s memory of that problem. Always ensure that the root cause of any fault is identified and corrected to prevent recurrence.

Before clearing the codes, it is a good practice to always save the report on your scanner. Most of the time, you will not need to come back and look at the stored report, but if you are trying to troubleshoot an intermittent issue, one of the fault codes could be the Holy Grail and point you or your mechanic in the right direction.