Parameters are set for the computer to recognize
malfunctions. Generally, the TPS has an operating range of
.5V to 4.5v. Any reading above or below those parameters
will cause the PCM to ignore the sensor, default to a "fail-
safe" mode (FMEM - Failure Mode Effects Management). A
Lean code can mean that there isn't enough fuel to
support Stoichiometric air/fuel ratios or perhaps the O2
sensor is open or shorted to ground or power. The
acceptable voltage parameters for an Oxygen sensor are
from .1V to 1.0v with the engine at operating
temperature. The best way to diagnose this concern is
with a Break-Out box or by pinning-out voltages at the
sensors/actuators and at the PCM connector as well as
testing the continuity of the harness from the PCM to each
Actuator/Sensor. Or you could throw parts at it until you
get lucky.