Wire up an "A/F gage" w/o effecting existing control system?

[Walter Sherwin]

FWIW,   I have a Haltech AF30 digital A/F indicator spliced into the O2
circuit of my GM PCM.  I also have an isolation switch which can decouple
this device from the PCM's O2 circuit.   Using an ALDL scanner I can monitor
the effect of "connected" versus "unconnected" upon the PCM's interpretation
of the O2 signal.  In my particular case the PCM's interpretation, with the
device connected, is biased approximately +100mv versus the unconnected
state.   Measurable, but not noticeable to a driver.

I would think that you should be safe, as long as you stay away from the
real "cheapies"  and query the vendor's tech people regarding this issue
before purchase.

Walt.



Date: Mon, 28 Feb 2000 09:11:19 -0500
From: Aribert_Neumann at magna.on.ca
Subject: Wire up an "A/F gage" w/o effecting existing control system?

I asked this question a while back as part of a larger series of questions
but
did not get a response.  Can I hook up a cheapie "A/F gage" like a Cyberdyne
brand by simply splicing into the wire from my O2 sensor or will the A/F
gage
degrade the signal from the O2 sensor to such an extent that I need to use
an A
/ B switch to switch the O2 signal between the A/F gage and the ECU?   FWIW,
I
am using a Bosch Motronic M1.5  engine management system (originally on a
2.0L
GME engine) grafted onto a 2.3L Isuzu engine.




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