Coolant Temp affects Fuel Control? (Datalogger)

[Rx3]

Ok I was running some logs on my car, and I've come up with a weird code:

PO 125: Insufficient Coolant Temperature for Closed Loop Fuel Control.


How does Coolant Temp affect my fuel system?


I already know I'm running a bit rich (carbon on exhaust, Fuel Trim bank 1 CEL).... only fuel mods of note that I have are the Walbro 190lph.

I need to know exactly what the closed loop fuel control does, and if I need to be worried about it.


Funny how these things always pop up just as you are about to buy the good parts (i.e. turbo)


Any help or insight would be appreciated.

 

[markmakeitso]

i don't have a logger, but generally there are open and closed loops which control the mixture settings of the engine. open loop happens when you do a cold start and the engine uses predetermined settings for mixture. when the engine warms up sufficiently for the o2 sensor to give correct readings it switches to closed loop operation, where the o2 sensor controls the mixture. often the coolant temp readings are used by the ecu to determine a good time to switch to closed loop operation.

that's just a general explanation, not a complete or even dsm-specific one.

 

[Kevin Jewer]

That is right. If the ECU thinks the engine is still cold, it runs in an open loop mode, quite rich. Like the choke on a carburated car. Perhaps a bad temp sensor. The interesting thing is the ECU must keep track of how long its in this choke mode in order to determine that it should be closed loop by now and throw a code... Interesting.

 

[Rx3]

Thanks guys

 

[Rodman]

I always though of closed loop as the ecu closing out input from sensors, and open loop as the ecu opening itself up to sensor input. It seems I have it backwards

 

[Kevin Jewer]

yes.

The term closed and open loop is used all over the place. Anytime sensors are used for feedback control it is considered closed loop. The ECU senses something from a sensor, makes a change, and its sees the change in the sensor, and changes it again, etc. That is the "loop" in closed loop. Open loop is a false statement, since there is no "loop" but it implies the opposite of closed loop just the same. In open loop there is no feedback control loop, and changes are made based on fewer sensors (airfow, temp, load, etc) and simply plugs those values in, and out comes a number that is output to the injectors, coil igniters, whatever.