DIY_EFI Digest V5 #39,toyota o2

[Greg Hermann]

>Date: Tue, 25 Jan 2000 13:08:37 -0700
>From: bearbvd at cmn.net (Greg Hermann)
>Subject: Re: Greddy air-fuel ratio meter
>
>>Almost looks good, anyone have any details about the 4 wire Toyota O2
>>sensor, the tech guy at greddy's said it can read 18-8:1, but not to be used
>>for initial tuning????.
>>They want $300, for theirs.
>>Grumpy
>
>Sounds like it must be the Bosch sensor--that one uses four wires--anybody
>know for sure??
>
>
>Grumpy/Greg
>
>The Toyota sensor can in fact measure a broad range of a/f ratios but so far,
>there is little information we have in the US as to how it actually works.
>
>The sensor does have 4 wires, B+ for heater, ground for heater - controlled by
>ecm (pwm), afr+ which supplies +3.3v from the ecm to one side of the
>sensor, and
>afr- which the ecm supplies +3.0v to the other side of the sensor.
>
>We do see a variable voltage when using a scanner tool but when you measure the
>sensor itself, voltage is not moving with major shifts in afr????  The general
>thought is that it  monitors the amperage and the direction of current flow to
>determine the afr. The scan tool voltage is a calculated # to give diagnostic
>functions.
>
>Very good and incredibly accurate sensor which operates in a linear fashion to
>afr.
>
>This will probably add more questions than it answers but it is a start.
>
>Scott

I suspect that Frank Parker is right. The NTK sensors started out life with
seven wires, went to six, then to five. Sounds like this may well be a four
wire iteration of it that Toyota is using. If so, the Greddy meter might be
a pretty good deal indeed.

Greg
>>
>
>
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