ECM and trouble codes

[hullroad]

In the early days of computer controlled cars we were taught an ecm could operate in one of two modes, "open" or "closed" loop. When in closed loop (warm engine) the ecm was gathering information from all sensors and commanding the engine to run at optimum performance based on the information it received. If the ecm were operating in open loop (cold) it told the engine to run on preprogrammed "base" information.....SO...in closed loop you get the best possible performance and fuel economy and in open loop you would not.
They additionally told us that their were "soft" codes and "hard" codes. The soft codes may or may not have triggered a steady check engine light but they could not cause a (warm) engine to operate in open loop. The hard codes always set the check engine light and always force the engine to run in open loop.
I would guess that the ecm in the insight still needs open loop for a cold engine and closed loop for a warmed engine but do they still have hard and soft codes......Meaning can driving an insight with ANY check engine light on cause the ecm to run on base information and "KILL" your MPG or are their some codes that still allow the engine to operate in closed loop. I know the "problem" that caused the light to trigger may cause poor fuel economy but do all codes cause an open loop operation.

[Willie Williford]

No!

Willie

[Insightful Trekker]

Highly technical question. :O

Your generalities do apply, but their oversimplifications.

Willie's answer is clear and succinct to your question in summary (the last one).

SAE's OBDII technical manual would answer all your specific questions, several hunderd dollars last time I checked. And a _VERY_ dry read (HIGHLY technical, requires a lot of advanced automotive knowledge to readily understand).

HTH!