Pre-code

Pre-code is a term describing boost cut by the ECU before logging a Volvo DTC - Diagnostic Trouble Code

“Pre-code” is a term I just invented to describe a situation where my Volvo has determined that something is irregular, but before it logs a diagnostic trouble code (DTC). Also, by definition, a pre-code is something that happens before a Check Engine light, since a DTC is a requirement of a Check Engine light.

I can tell when my 850 T5 is in a pre-code condition because it cuts my 850′s boost in half. I can easily feel this when accelerating, and can measure it because I installed a boost gauge in my Volvo 850.