Clear fault codes only after the initial scan has been saved and the cause investigated, because a code is a starting point for diagnosis and not a repair.
What a fault code tells you
A fault code records a condition recognized by an electronic controller. It is a starting point for diagnosis, not a parts replacement instruction. The same complaint can involve several controllers, and a fault associated with one component may be caused by a wiring, power supply or operating-condition problem elsewhere.
Identify the system and save
Begin by identifying the vehicle and the system reporting the fault. Use a compatible application and communication adapter, then save the initial scan. Record the complete fault identifier, status, occurrence information and any available event data. Note the customer's description of when the problem happens so the stored information can be compared with the complaint.
Read the manufacturer’s procedure
Read the manufacturer's fault description and diagnostic procedure for that controller. Review related faults and relevant live data before deciding which check to perform. An active code needs to be interpreted alongside the controller's detection conditions; an inactive code can still be useful when the symptom is intermittent. Avoid clearing either simply to make the initial report look clean.
When to clear fault codes
Clear faults only at the appropriate stage of the repair process and with the correct tool permissions. Clearing stored information does not fix the cause, and an unresolved fault may return when its detection conditions are met. Some emissions-related records have special retention or clearing rules, so a code that remains visible is not automatically evidence that the tool failed.
Verify and hand over the repair
Verify the repair using the manufacturer's required checks and the relevant operating conditions, then save the final report. Compare it with the original scan and explain any remaining information. A useful handover states the cause found, the work performed and the evidence supporting the result, rather than only saying that the fault list was erased.
More reading on clear fault codes
Two related guides explain SPN and FMI numbers and active compared with inactive status. The formal message definitions are published by SAE, and the reference document shows the standard behind these diagnostic messages.
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