Step 3:
Process of Elimination
•
A-C resistance stayed the same in steps 1 & 2. Therefore, either “A” or “C” is the
Ground connection.
•
A-B resistance increased from ~500
Ω
to ~9500
Ω
from Step 1 to Step 2. Therefore,
“A” or “B” is the ground connection.
•
“A” must be the Ground
connection since “B” cannot be the ground connection as
a result of Step 1.
•
“C” must be the +5 Volt
connection, since “A” is not.
•
“B” must then be the Output Signal
.
Another way to look at the TPS’s electrical functionality is to realize that it simply creates an output
that is either biased to Ground or to +5 Volts. At closed throttle, the output should be biased to ground, and
at full throttle, the output should be biased to +5 Volts. See
Figure G.2.2
for an electrical schematic of a
typical potentiometer. Please note that the TPS must use a (roughly) 10k
Ω
potentiometer! Failure to do so
will result in improper impedance matching for the
TECgt
, and a false sensor reading will result.
Fortunately, most TPS’s are of the 10k
Ω
variety.
Fig. G.2.2:
Potentiometer functionality for closed and open throttle conditions.
TPS Functionality and Wiring
The TPS allows the
TECgt
to provide fuel enrichments for various throttle movement situations,
like an accelerator pump on a carburetor. For high rpm, closed throttle situations, (like deceleration or
engine braking), it can be used to turn off the fuel flow completely. The TPS is also used to detect closed
throttle for the activation of the Idle Air Control parameter. See
Section B.4
for tuning the TPS-related
functions.
Many different TPS’s have been used by OEM’s in the past few decades. The most common types
are driven directly on the throttle shaft by either a dowel pin going through the shaft of a “D” shaped
throttle shaft. Various TPS styles are available from Electromotive, as outlined in
Figures G.2.3-5
.
Arm-Style TPS
GM Dowel-Pin Style
PN 310-71310
PN 310-71320
Fig. G.2.3
Fig. G.2.4
______________________________________________________________________________________
TECgt Manual Version 2.0
- Page 88 -
©2008 Electromotive, Inc.
