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Discussion Starter #1
Probably looking for an answer from CharlieX. Is there an easy way to determine if the ECU remains "on" after engine shut down.
Michael
 

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The can bus stays active, the relays don't click off, the circ fans run.

It'll run for about 15 seconds normally after shut down, and it'll run for longer if the temperature is high.

Its also possible to screw up the mapping so badly it'll stay on til you remove the battery and keep the engine running, ask me how i know ( answer don't test your remote control software on a flakey wireless link in the driveway)
 

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Discussion Starter #3
Charlie, here is exactly what and why I am asking.
In excess of 190'F at engine shut down the ECU remains active to monitor for temperatures in excess of 230'F to turn on the re-circulation pump. I want to know if the ECU has reached the 190'F set point and remains on so that I know there could be a chance that the re-circulation pump will kick in. I have a shut off valve in the heater supply and if the ECU is still on I will open that valve, if not I can leave it closed.
Michael
 

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The circ only stays active if its above that temperature, so if what you're asking is what i think it is, the easiest way is to put a sense on that ?

The ECU shouldn't stay on longer than 15 seconds or so, unless the temperatures are already over the threshold, since once the engine is off, the temps aren't going to rise much.

I'll check on my bench ecu but i'd imagine some of the VRef's stay active when the ecu is still on.

I can't remember if the ACC stays energised in the car ( it'll probably float so a diode or such), but otherwise if you need a sense you can pick it up off the key circuit.
 

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Discussion Starter #5
Since there is only one engine temperature sensor for all functions I would conclude that if the dash temp readout displays under 190'F the ECU would turn off and there could be no chance of the Re-circ. pump coming on. Over 190'F on the readout means the ECU is on. Would you agree?
Michael
 

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Yep i think we're saying the same thing, if the temp's are above the threshold for the recirc pumps, the ecu stays on, but if they're not it turns off after 15 or so seconds.

There would be no point staying on and monitoring temps at low temps for it to reach 230F since that'd be impossible.

it'll stay on for about 20 minutes at most.
 

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Discussion Starter #7
I was not sure if the displayed temp was the same as the ECU used for its threshold.
Two engineers comunicating can be tough ;-)
Yep i think we're saying the same thing, if the temp's are above the threshold for the recirc pumps, the ecu stays on, but if they're not it turns off after 15 or so seconds.

There would be no point staying on and monitoring temps at low temps for it to reach 230F since that'd be impossible.

it'll stay on for about 20 minutes at most.
 

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Discussion Starter #9
With the engineer mentality I am never comfortable unless there is proof. I wish there could be an LED that would indicate ECU is powered. Some how I don't trust that just because the temp. shows 189 the ECU is off or at 191' it is on:shrug:
 

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totally agree on that one, its problematic for me because its possible to get the ecu into a state where you can't turn it off without disconnecting the battery.

i'm not by my bench ecu but when i am i'll see whats lit up when its on.
 

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Discussion Starter #11
That would be very helpful, thanks
totally agree on that one, its problematic for me because its possible to get the ecu into a state where you can't turn it off without disconnecting the battery.

i'm not by my bench ecu but when i am i'll see whats lit up when its on.
 
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