Actron CP9087 - Manual (Page 15)

THROTTLE POSITION Sensor/Switch
2-7
• Sometimes a second switch is used to signal a wide
open throttle condition. This switch is normally open (or
closed - depends upon vehicle) when the throttle is at
idle or just partially open. The switch operates when the
throttle is opened beyond a certain point. (The amount of
throttle opening required to operate the switch varies
with vehicle.)
The computer uses throttle position to determine engine
operating condition: idle (closed throttle), cruise (part
throttle), or hard acceleration (wide open throttle). The
computer can then properly control air/fuel mixtures, spark
advance, idle speed, and lock-up torque converters.
How it is
used?
Location
Fuel injected engines: Rotary type sensor - usually
mounted to outside of throttle body and linked to throttle
shaft.
Computer controlled carburetor engines: Linear (sliding)
type - usually mounted inside carburetor (GM) or outside
carburetor (Ford).
When to
Test
• Related trouble codes sent by computer.
• Driveability problems such as hard starting, rough idle,
stalling, hesitation, stumble, surging, knocking (pinging),
poor fuel economy, backfiring, no torque converter lock-up.
What to
Inspect
Sensor operation (see test on page 2-10) or switch
operation (see test on page 2-12). Poor connections at
sensor or computer. Sensor position adjustment. Faulty
sensor wiring (open or short circuits). Binding throttle shaft
or linkage. If used: “Cruise Control” linkage problems, idle
speed control motor, vacuum hose connected to throttle
positioner, choke, or cam systems affecting throttle
position.