Pontiac Fiero 1988 Service Manual page 650

DRIVEABILITY A N D EMISSIONS - FUEL cftJECTIOft (PORT) 6E3-C1-1
SECTION CI
ELECTRONIC CONTROL MODULE (ECM) AMD SENSORS
GENERAL DESCRIPTION . . . . . . . . . . . .
ELECTRONIC CONTROL MODULE (ECM) . . C1-1
ECM Function
...................
C1-1
PROM • • . • • • a o o o « > o o . 0 0 » » e » o o o < > o
C1 " 1
C^\ L P^\ K . . . . . . . . . . . . 9. ..OO. .CO..
CI "2
INFORMATION SENSORS
. . . . . . . . . . . . . C I - 2
Engine Coolant Temperature Sensor . * CI-2
MAT Sensor
. . . . . . . . a . . . . . . * . . . . .
C3-2
IVI^VPSensor #««@©®0©©©©®®s©©e«@0© CI
Oxygen (0
2
) Sensor . . . . . . . . . . . . . . . .
a - 3
Throttle Position Sensor (TPS) . . . . . . . . CI-3
Park/Neutral Switch (Auto Trans. Only) . CI-3
A/C " O n " Signal o » . . . . . .
CI-3
Vehicle Speed Sensor (VSS) C1-3
Distributor Reference Signal . . . . . . . . . C1-3
DIAGNOSIS . .
a o . . . . . . . . . . . . . . . . . • . . .
CI«4
E CIVI
« * e . e . « e e » 9 0 » e > 9 o « e e o . . o . o e < 3 o o
C I
PROM C I - 4
ECM INPUTS
o
o . . . . . . . . . . . . . o . CI "4
GENERAL DESCRIPTION
ELECTRONIC CONTROL MODULE (ECM)
The Electronic Control Module (ECM) (Figure Cl-
1), is the control center of the fuel injection system. It
constantly looks at the information from various
sensors, and controls the various systems that affect
vehicle performance. For service, the ECM has three
parts: a separate Controller (the ECM without the
PROM), a separate calibrator (PROM), and a
CALPAK.
CONTENTS
C1-1
P H
ECM
PH ECM HARNESS
CONNECTORS TO ECM
[ 3 1 PROM ACCESS COVER
4S 1196-6E
Figure C1-1 Electronic Control M o d u l e (ECM)
Coolant T e m p e i a t u r e Sensor . . * c . , . .
C1-4
MAT S e n s o r . . . . . . * . . . . . . . . . « C1-4
O2 Sensor * . . . . . . * . C1-4
TPS . . . . . . . . . . .
. . . . . . - . . . . O . . . .
C1-5
MAP S e n s o r e . . . * o . . , o . . . , « . c • . C I - 5
VSS . . . . . . . 9 » o * e . . « . o . e . . » » . . . . C1 "5
P/N Switch C l - 5
A/C Request Signal
o . . . . . . . . . < > , . . . .
C1-5
Reference
Signal
. .
o . . * « . . « » o . . . . .
C1-5
ON-CAR SE1¥;€E
c « . . c .
C1-5
ELECTRONIC CON TvOL [MODULE (ECM) . . C1-5
PROM/CALPAK , . . . . , . . . . . . . C I - 6
Functional
Check
- c o * . . . . . C1-7
COOLANT S E N S O R . * . . « . . . . . . . . . . . . . . C I - 7
MAP SENSOR . . . . . . . . . . . . . . . . . . . . . . .
CI-7
MATSENSCR , . . . . . - . . . . . . . . . . . . . . . €1-7
OXYGEN
SENSOR . . . , . . . . . . . . . . . . . . . C l - 8
THROTTLE POSITION SEMSOR (TPS) C1-B
PARK/NEUTRAL
SWITCH
e
« . . , , , c
„ . . . . C1-9
PARTS INFORMATION . . . - . . C I - 9
ECM Function
The ECM supplies either 5 or 12 volts to power-
various sensors or switches. This is done through
resistances in the ECM which are so high in value
that a test light will not light when connected to the
circuit. In some cases, even an ordinary shop
voltmeter will not give an accurate reading because
its resistance is too low. Therefore, a 10 meg ohm
input impedance digital voltmeter is required to
assure accurate voltage readings.
The ECM controls output circuits such as the
Injectors, idle air control (IAC), A/C Control Relay,
etc., by controlling the ground circuit through
transistors in the ECM.
PROM
To allow one model of ECM to be used for many
different cars, a device called a Calibrator (or
programmable read only memory PROM) is used (see
Figure
Cl-2).
The PROM is located inside the ECM,
and has information on the vehicle's weight, engine,
transmission, axle ratio, and other components. While
one ECM part number can be used by many car lines,
a PROM is very specific and must be used for the right
car. For this reason, it is very important to
check
the
latest parts book and Service Bulletin information for
the correct part number when replacing a PROM.
An ECM used for service (called a controller)
comes without a PROM. The PROM from the old ECM
must be carefully removed and installed in the new
ECM (see On-Car Service).