Pontiac Fiero 1988 Service Manual page 651

6E3-C1-2 DRIVEABSLITY A N D EMISSIONS- FUEL INJECTION (PORT)
CD
E C M
[Y]
PROM C A R R I E R
•0
PROM ( E N G I N E C A L I B R A T O R )
\T]
C A L P A K
4 S 1 2 1 7 - 6 E
Figure
CI-2
PROI V 1
(Calibrator) and CALPAK
CALPAK
A device called a CALPAK is used to allow fuel
delivery if certain parts of the ECM should fail. It has
an access
d o o r
in the ECM, and removal and
replacement procedures are the same as with a
PROM.
If the CALPAK Is missing, a Code 52 will be set.
I N F O R M A T I O N SENSORS
E n g i n e C o o l a n t T e m p e r a t u r e Sensor
The Coolant sensor (Figure Cl-3) is a thermistor
(a resistor which changes value based on temperature)
mounted in the engine coolant stream. Low coolant
temperature produces a high resistance (100,000 ohms
at -40°C/-40°F) while high temperature causes low
resistance (70 ohms at 130°C/266°F).
4-2-85
ENGINE COOLANT TEMPERATURE SENSOR
HARNESS CONNECTOR TO ECM
LOCKING TAB
*5S 164Q-6EA
Figure C1-3 Engine Coolant Temperature Sensor
The ECM supplies a 5 volt signal to the coolant
sensor thru a resistor in the ECM and measures the
voltage. The voltage will be high when the engine is
cold, and low when the engine is hot. By measuring
the voltage, the ECM knows the engine coolant
temperature. Engine coolant temperature affects most
systems the ECM controls.
A failure in the coolant sensor circuit should set
either a Code 14 or Code 15. Remember, these codes
indicate a failure in the coolant temperature circuit,
so proper use of the chart will lead to either repairing
a wiring problem or replacing the sensor to properly
repair a problem.
M a n i f o l d A i r T e m p e r a t u r e ( M A T ) Sensor
The manifold air temperature (MAT) sensor is a
thermistor (a resistor which changes value based On
temperature) mounted in the Air Cleaner Assy. Low
temperature produces a high resistance (100,000 ohms
at -40°C/-40°F) while high temperature causes low
resistance (70 ohms at 130°C/266°F).
The ECM supplies a 5 volt signal to the sensor
thru a resistor in the ECM and measures the voltage.
The voltage will be high when the incoming air is cold,
and low when the air is hot.
A failure in the MAT sensor circuit should set
either a Code 23 or Code 25.
M a n i f o l d A b s o l u t e Pressure ( M A P ) Sensor
The manifold absolute pressure (MAP) sensor (see
Figure Cl-4) measures the changes in the intake
manifold pressure which result from engine load and
speed changes, and converts this to a voltage output.
[TJ]
M A P S E N S O R
4 S 0 5 5 2 - 6 E
Figure CI-4 SV1AP Sensor
A closed throttle on engine coast down would
produce a relatively low MAP output, while a wide
open throttle would produce a high output. Manifold
absolute pressure (MAP) is the OPPOSITE of what
you would measure on a vacuum gage. When manifold
pressure is high, vacuum is low. The MAP sensor is
also used to measure barometric pressure under
certain conditions, which allows the ECM to
automatically adjust.for different altitudes.
The ECM sends a 5 volt reference signal to the
MAP sensor. As the manifold pressure changes, the
electrical resistance of the sensor also changes. By
monitoring the sensor output voltage, the ECM knows
the manifold pressure. A higher pressure, low vacuum
(high voltage) requires more fuel, while a lower
pressure, higher vacuum (low voltage) requires less
fuel.