Pontiac Fiero 1988 Service Manual page 518

DRIVEABILITY AND EMISSIONS - FUEL INJECTION (TBI) 6E2-C1 1
SECTION C1
ELECTRONIC CONTROL MODULE (ECM) AND SENSORS
CONTENTS
GENERAL DESCRIPTION . .
ELECTRONIC CONTROL MODULE (ECM) ,
PROM .
ECM FUNCTION *
INFORMATION SENSORS . . . .
Engine Coolant Temperature Sensor
MAP Sensor . . . ,
MAT Sensor . . •
Oxygen (O2) Sensor • . 0 . . . .
Throttle Position Sensor (TPS)
Park/Neutral Switch . . .
A/C Request Signal
Vehicle Speed Sensor . .
Crankshaft Sensor
DIAGNOSIS . . . . . . . . . . . . . . . . . . .
ECM ,
PROM
ECM INPUTS
Coolant Temp. Sensor
MAP Sensor . ,
C1-1
C1-1
C M
C I -
C l -
C l -
C1-
C l -
C1-
C l -
C1-
ci - 4
ci-4
ci-4
C1-4
C I - 5
C1-5
C1-5
CI-5
C1-5
-2
-2
-2
•2
~3
-3
-3
-3
GENERAL DESCRIPTION
ELECTRONIC CONTROL MODULE (ECM)
The electronic control module (ECM) (Figure Cl-
1), located under the instrument panel, is the control
center of the fuel injection system. It constantly
monitors the information from various sensors, and
controls the systems that affect vehicle performance.
The ECM performs the diagnostic function of the
system. It can recognize operational problems, alert
the driver through the "Service Engine Soon" light,
and store a code or codes which identify the problem
areas to aid the technician in making repairs. See
"Introduction" for more Information on using the
diagnostic function of the ECM.
For 1988, the ECM used in 2.5L equipped vehicles
will be a type, called GMP4. For service, this ECM
consists of only two parts; a controller (the ECM
without a PROM), and a calibrator, called a PROM
(Programmable Read Only Memory).
PROM
The PROM is programmed with information
relative to a certain vehicle (vehicle weight, engine
type, transmission type, axle ratio, etc.) This allows
the PROM to calibrate the ECM control for most
efficient vehicle operation.
MAT Sensor C1-5
Oxygen Sensor . . . . . . . . C1-5
TPS . « « * « . « « » . . « « . « . * . * . . . . « . . » C1 "5
VSS * C1-5
P/N Switch C1-5
A/C Request Signal • • • C1-5
DIS Reference Signal . C1-5
ON-CAR SERVICE C I - 6
ELECTRONIC CONTROL MODULE (ECM) . . C1-6
ECM AND COMPONENT REPLACEMENT . . CI-6
PROIVI « . » o . « . o o » e o * o < > c o o . . . . . . . 00 C1 "7
Functional Check *
« . o . . « < > . . .
C1-7
COOLANT SENSOR C1-7
MAP SENSOR C1-8
MAT SENSOR C1-8
OXYGEN SENSOR . C1-8
THROTTLE POSITION SENSOR (TPS) . . . . . C1-9
PARK/NEUTRAL SWITCH . . . . . . . . . C1-9
PARTS INFORMATION C1-9
m
E C M
[T]
P R O M
[T1
A C C E S S C O V E R 7S 3327-6E
Figure C M - Electronic Control Module (ECM)
While one ECM part number may 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 comes without a PROM.
The PROM from the old ECM must be carefully
removed and installed in the new ECM. (See On-Car
Service.)