Pontiac Fiero 1988 Service Manual page 663

6E3-C1-14 DRIVABILITY AND EMISSIONS - FUEL INJECTION (PORT)
MANIFOLD
ABSOLUTE
PRESSURE
(VACUUM)
MAP SENSOR
B C
MM)
ECM
TO TPS
416 GRY
C14
432 LT.GRN
469 BLK/RED
C11
C12
D13
TO M A T SENSOR
- A A A A A / — 5V REFERENCE
— MAP SIGNAL
THROTTLE BODY
" BACKUP SIGNAL
5-22-87
5-8-87
5 S 1 9 1 5
- CHART C-1D
MAP OUTPUT CHECK
.2.81 "P" SERIES (PORT)
Circuit Description:
The manifold absolute pressure (MAP) sensor measures manifold pressure (vacuum) and sends that signal
to the electronic control module (ECM). The MAP Sensor is mainly used for fuel calculation when the ECM is
running in the throttle body backup mode. The MAP is also used to determine the barometric pressure and to
help calculate fuel delivery.
Test Description:
Numbers below refer to circled
numbers on the diagnostic chart.
1. Checks MAP sensor output voltage to the ECM.
This voltage, without engine running, represents
a barometer reading to the ECM.
2. Applying 34 kPa (10 inches Hg) vacuum to the
MAP sensor should cause the voltage to be 1.2
volts less than the voltage at Step 1. Upon
applyng vacuum to the sensor, the change in
voltage should be instantaneous. A slow voltage
change indicates a faulty sensor.
The engine should be running in this step or the
"Scanner" may not indicate a change in voltage.
The "Service Engine Soon" light may come "ON"
and the system may set a code during this test.
Check vacuum hose to sensor for leaking or
restriction. Be sure no other vacuum devices are
connected to the MAP hose.