Is it fairly common or rare for fault codes, associated with check engine light, to clear themselves, and not show up in ecu history in Techstream?
Fault codes
- Thread starter Ptrott
- Start date
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It’s actually fairly common for some check engine light (CEL) codes to clear themselves—but it depends on the type of problem. (OBD-II system) continuously monitors sensors and systems. If it detects a problem, it stores a fault code and may turn on the light. But:
If the issue was temporary or intermittent, and
The system passes its self-checks for a certain number of driving cycles
…the computer can automatically turn the light off and mark the code as “history” instead of “active.”
Common situations where this happens
Loose or slightly open gas cap (very common)
Brief sensor glitches (like oxygen sensor fluctuations)
Temporary misfires (e.g., from bad fuel or moisture)
Short-lived emissions irregularities
If the issue was temporary or intermittent, and
The system passes its self-checks for a certain number of driving cycles
…the computer can automatically turn the light off and mark the code as “history” instead of “active.”
Common situations where this happens
Loose or slightly open gas cap (very common)
Brief sensor glitches (like oxygen sensor fluctuations)
Temporary misfires (e.g., from bad fuel or moisture)
Short-lived emissions irregularities