Ray,
I'm not particularly familiar with Toyota, however i do have a fair
amount of experience reverse engineering automotive electronics.
How many O2 sensors do you have? I ask this because there may be one,
two or four sensors. Generally they are named upstream and downstream.,
left bank/right bank or something similar. If you have two sensors and
s specific sensor(guessing downstream) is giving problems, then you have
a better idea as to the mode of reception.
Down stream sensors are placed farther away than upstream which makes
them more receptive to RFI. The exhaust can end up being the culprit. A
common mistake is to assume the unibody and exhaust are gnd. When we
apply radio engineering disciplines to the body and exhaust it becomes
evident, in this case, that a RF potential can develop between the
motor gnd and the O2 gnd(which is distributed).
Another important detail is the type of sensor. Is it wide band or
normal? Yet another detail, is it a heated sensor? And Finally, have
you inspected the sheath? Is it shielded? If so, what type. braided,
tinsil, etc.
Without more information, i'll take a stab at it and suggest that in
addition to wrapping the O2 leads with braid, you need to add a wide
braided ground strap at the point of the O2 sensor to body ground.
Think in terms of RF propagation and you'll probably see the problem
right away.
Good luck,
Steve
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