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ECU - What does it NOT control?

337 Views 6 Replies 4 Participants Last post by  SpyderVenom
I'm going to install a new aftermarked ECU now. But I'm not sure if the original ECU is controlling the Powerstering and stuff like that. I'd hate to get any kind of malfunctions due to the new Engine control unit..

I'm trying to determine if I could just totaly replace the stock ECU with a new Megasquirt and still retain functions such as Powersteering and so on.

Can anyone tell me exactly WHAT I will loose when I remove the stock ECU? The MegaSquirt will control ignition and fuel, i'll reuse all the original sensors exept for the AFM wich will be replaced by the MS onboard MAP sensor.
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p/s, airbags, signals+lights, wipers, umm what else is on a car... lol... are not controlled by the engine control unit.
The P/S IS partially controlled by the EMS. There is a +12v signal coming from the ECU to the P/S that will turn off the P/S. The A/C might be - I know there is an A/C input that will increase the idle but I don't know if there is an A/C out from the ECU that engages the pulley clutch.
SpyderVenom said:
The P/S IS partially controlled by the EMS. There is a +12v signal coming from the ECU to the P/S that will turn off the P/S. The A/C might be - I know there is an A/C input that will increase the idle but I don't know if there is an A/C out from the ECU that engages the pulley clutch.

oh yeah that would make sense because the p/s in our cars is like... only activated when you're at certain speeds
The ECU tells the P/S to turn on when the engine is running - off when the key is ON but engine stopped or during cranking. The P/S tells the ECU to idle up when it is active. So there are 2 wires connecting between the ECU and P/S control unit. On my AEM I set the the output from the ECU to the P/S to only turn on if engine speed is > 400 RPM. HTH
Hmm.. So I guess I must retain the ECU then, and somehow keep the wires going to/from the PS and AC, and let the MegaSquirt control the rest..? Damn.. I was planning on selling it to this guy.. :\

The PS is giving max PS assistance when you are standing still or driving slowly, then above a sertan speed it will dissengage. Max power steering at high speeds can be dangerous.. :\
On my AEM, I depinned the wire to the PS pump so I get full PS boost all the time. I don't have a problem. The AEM has everything that you need to run the AC, I just don't know if it controls the pulley clutch - I took my AC out. I've never played with the megasquirt so I don't know what that does or doesn't control.
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