Do you have an article you'd
like to send in?
(Members only)
SUBMIT
|
|
FYI - TPS OPERATION
Submitted by Bluegrass / 08-02-06
The TPS is a sensor that
provides the computer with a variable voltage that represents the position
of the throttle.
This position information is used to sense 'rate of throttle opening', control
air/fuel ratios, ignition timing, fuel shut down at deceleration, EGR functions
at cruise, air conditioning cut-off and computer updating when the system has
the least to keep track of.
The computer does an automatic self zero "reference" function
with the TPS output voltage.
Said another way, the input voltage from the
TPS to the computer becomes a zero reference
from its starting value in order to represent
the actions and functions that are to take
place.
This zero function takes away the need for
production precisions of manufacture and mounting
vs. voltage precisions, making the absolute
setting much less important.
What this means is the "absolute value" of
the TPS setting in not of great importance.
However, there is a specified requirement
that it be within +/- 3% for this self zero
function to take place properly.
The usual given setting at throttle rest of
.96 to .99 volt is not cast in stone due to
the self zero that the EEC does each time
the ignition is turned on. This action up
to now has been little known and as such,
too much emphasis has been places on an exact
value.
Testing and setting the TPS output is measured
between the black and green leads at the sensor.
Many try to measure between the green lead
and chassis ground and get an improper reading
and try to adjust to it. The reason this is
not proper is the black lead color is usually
taken as a ground standard color. In this
system this black lead is "
isolated" from chassis ground because
the power comes from a 5 volt supply in the
computer that has neither its positive or
its negative side referenced to ground but
does have it's center tap grounded and still
is not a reference for measuring properly.
The value setting needs to be done with a
digital voltmeter and should measure a value
at least 4.5 volts at wide open throttle and
be smooth and continuous without breaks.
After setting new value, the computer will
self-adjust after several starts to addres
all the function the TPS supplies position
information for.
Closed throttle values within .9 and 1.0
volt usually will be accepted by the EEC.
This is only one-tenth of one volt and is
within all the guidelines for production,
environment and installation conditions.
There are many who will disagree with this
position at first but I urge all to re-read
the text and consider the overall reasons
and practical applications for mass production
use of this sensor.
Why the absolute setting is not so important
to the .001 volt level is that it will and
can change due to heat, wear and varying
supply voltage as there are other sensors
using the same 5 volt supply and cause the
loading on that supply to change during operation.
|
|
|
