I know u can check if u are in open or closed loop with teh paper clip trick...well...what speed will the SES light blink at in open and closed loop? I tried the trick right after starting the car(open loop)then drove around for like a half hour and was running at around 150*(i always have one fan on...the other is run with a toggle switch) I do have a Stage 2 fastchip but Ed Wright told me he doesn't change the open loop/closed loop setting...so i don't think i'm getting into closed loop which would explain gas mileage...so i need to know is there a big difference in SES blinking speed between open and closed loops? thanks

Also if i'm not hitting closed loop what can cause this? The O2 sensor is faily new as well

THANKS!

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Tony

 

I can't tell about the blinking light stuff...I use an auto x-ray that tells you open/closed loop, however, any significant trouble code will cause your car to go into limp home mode which will destroy your gas mileage. A bad coolant temp sensor will also prevent your car from going closed loop and prevent TCC lockup which will cut your MPG to about 1/2. Just some ideas.

 

Open loop = 2.5 flashes per second
Closed loop = 1 flash per second

Rich = Always on
Lean = Always off
BSA

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Forgot one thing, you need to test for open/closed loop at a constant throttle speed other wise you could be seeing a rich condtition from acceleration enrichment or a lean condition due to deceleration.
bsa

 

i'm doing it at idle...i was told i can do that....can i?

 

You can, but sometimes the computer will kick the car into open loop at idle. Do it at speed. It gives you a better idea of what the engine is doing since its under load.
bsa

 

alright cool...thanks for the info

 

This is so cool this topic just came up, until i get my laptop running i was thinking of doing this jst to get an idea of where my block learns are.

bsa - by rich/lean, do you mean the car is running rich/lean, or that the computer is commanding rich/lean to make up for a lean/rich condition?

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Ed, how's that Manassas weather lately. Hope its better now than it was the last time I was around there.
What I meant was that when in Field Service Mode (fancy term for the above procedure) the computer runs the engine differently. In order to get a good idea of whether the engine is entering closed loop the engine must be operated at a constant speed. This is because of acceleration enrichment or another condition that calls for enrichment of the mixture. This would cause the SES light to stay solid for a period of time before returning to normal. Likewise in most cases if the engine is idling below 1200. But if the engine is constantly running rich or lean you will know because the light will always stay off or on. So to answer your question: BOTH. It will indicate 1)when the ECM is compensating for a rich or lean condition 2) when there is a rich or lean condition the the ECM cannot compensate for. i.e the O2 sensor is bad. This will most likely be accompanied by a code 44 or 45, however. Hope that wasn't too confusing. Its late and I've had my head in a Calculus book all day.
bsa

[This message has been edited by irocbsa (edited June 12, 2001).]