Re: Closed Loop Disable

[WEG1192@aol.com]

>From a thread a while back, nikog@mediaone.net writes:

<< Using just a DVM is a GREAT way of doing your first chip. You'll learn a 
lot
 with that method. Turn off closed loop/adaptation, then tune the maps to get
 450mv from the O2 sensor at all PT map locations. Note, you'll NEVER get the
 O2 to read 450mv; it'll either be above or below it. If changing the map
 value by one digit makes the O2 reading go from below to above 450mv (or
 vice-versa), rest assured that the tuning at that point is more than close
 enough. Heck, 5% off is close enough. This is exactly how I tuned my
 turbocharged M3. >>

How do you get the ECM to not use closed loop without a scanner? I 
disconnected the O2 sensor but was told that that would put the ECM into limp 
home mode, not open loop. My understanding was that if the ECM did not get 
the O2 cross counts, that it would stay in open loop.

Also, I thought you could use a DVM and measure the O2 signal (disconnected 
from the ECM) as a way to monitor tuning, but a recent post said the ECM puts 
a bias voltage on the O2 wire. How can that bias voltage effect a 
disconnected sensor? Is there a miscommunication here? Before each tuning 
session, should I remove power from the ECM each time to reset the BLMs to 
128?

Sounds to me like two DVMs are needed. One for the O2 sensor and one for the 
MAP sensor to know where you are on the RPM vs. MAP table?
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