Pontiac Fiero 1988 Service Manual page 529

6 E 2 - C M 2 DRIVEABILITY AND EMISSIONS - FUEL INJECTION (TBI)
MANIFOLD
ABSOLUTE
PRESSURE
(VACUUM)
5-1-87
M A P SENSOR
A B C
ECM
TO TPS
SENSOR
416 GRY W11 —AJ\J\f\ 5 V REF
432 LT. GRN
469 BLK
B20
W14
TO MAT
SENSOR
MAP SIGNAL
"1
SENSOR
— GROUND
" THIS WIRE MAY ALSO HAVE A TRACER COLOR
4-21-87
: 7S 3208-6E
C H A I T C-1D
MAP OUTPUT CHECK
2.5L "P" SERIES (TBI)
Circuit Description:
The manifold absolute pressure (MAP) sensor measures manifold pressure (vacuum) and sends that signal
to the ECM. The MAP sensor is mainly used to calculate engine load, which is a fundamental input for spark
and fuel calculations. The MAP sensor is also used to determine barometric pressure.
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. Comparison of
this BARO reading with a known good vehicle
with the same sensor is a good way to check
accuracy of a "suspect" sensor. Readings should be
the same ± .4 volt.
2. Applying 34 kPa (10" Hg) vacuum to the MAP
sensor should cause the voltage to be 1.2 volts less
than the voltage at Step 1. Upon applying vacuum
to the sensor, the change in voltage should be
instantaneous. A slow voltage change indicates a
faulty sensor.
3. Check vacuum hose to sensor for leaking or
restriction. Be sure no other vacuum devices are
connected to the MAP hose.