Pontiac Fiero 1988 Service Manual page 436

DRIVEABILITY AND EMISSIONS - FUEL INJECTION 6 E - 9
Park/Neutral S w i t c h
T h e
indication in
t h i s mode
may vary
w i t h
manufacturer so the type of reading for a particular
tool
should
be
checked
in the
operator's manual. The
important thing is
that the the
reading changes state
(switches)
when the
gear selector is moved
from
park/neutral to drive
or reverse,
Torqye Convenor Clutch (TCC)
In
this position,
the tool will
indicate
when the
T C C
has
been
commanded by
the E C M
to
turn
"ON".
This does
not
necessarily
mean that
the clutch
was
engaged but only
t h a t the
ECM grounded
the
circuit
internally. The best way to determine if the clutch has
engaged is to monitor
engine
rpm when
the
TCC
comes "ON".
EGR (Duty Cycle)
The
E G R
system
uses a
valve to feed
a
small
amount of exhaust
gas
back
into the
intake manifold
to control formation of NO
x
. Like all ECM outputs, the
"Scan"
tool only
indicates
t h a t
the ECM has
commanded the function,
and
does not indicate
that
the function has really happened.
EGR Position
This indicates the position of the EGR pintle.
Integrator and Block Learn
Normal readings for these positions are around
128. If higher, it indicates that the ECM is adding fuel
to the base fuel calculation because the system is lean,
and if the numbers are below 128, the ECM is taking
out fuel from the base calculation because the system
is rich. The integrator gives short term corrective
action, while the block learn portion (which is a long
term correction) will only change if the integrator has
seen a condition which lasts for a calibrated period of
time.
Block Learn Multiplier (BLM) Cell - or -
Block Learn Memory (BLM)
There are up to sixteen different cells,
corresponding to ranges of rpm and engine load
(indicated by MAF or MAP signals), and other
conditions, such as A/C or P/N switch "ON" or "OFF",
etc. The ECM learns how much adjustment is needed
in each cell, and retains it in memory, so that the
adjustment will immediately be made when the
engine operates in that cell (or rpm/load range). This
parameter will display what cell the ECM is currently
using for the fuel calculation.
IAC (Idle Air Control)
This system is used to control engine idle speed to
the desired rpm, for different operating conditions. In
this mode, the numbers will indicate the position to
which the ECM has moved the valve pintle. The ECM
moves the IAC in counts, or steps, and the number of
these counts are displayed on a "Scan" tool.
Desired RPM
This indicates the rpm to which the ECM is trying
to control the idle.
Shift Light
This displays "yes" when the ECM is commanding
the shift light to turn "ON".
PPSW (Pump Prime Switch)
This is the voltage on the fuel pump feed circuit.
The ECM will adjust fuel injector base pulse width
from this voltage value rather than from battery
voltage.
A/C Request
The state of the A/C signal line to the ECM is
shown. It should read "yes" whenever the A/C is
requested.
A/C Clutch
"ON" is displayed when the ECM has commanded
the A/C clutch "ON".
Knock Retard
This indicates the number of degrees the ECM is
retarding the electronic spark timing (EST).
Knock Signal
This displays a "yes" when knock is detected by
the ECM, and a "no" when knock is not detected.
Battery Voltage
This displays the battery voltage detected at the
ECM ignition input.
Fan
"ON" is displayed when the cooling fan has been
commanded "ON".