Pontiac Fiero 1988 Service Manual page 624

DRIVEABILITY AND EMISSIONS - FUEL INJECTION (PORT) 6E3-A-41
CODE 25
MANIFOLD AIR TEMPERATURE
(MAT) SENSOR CIRCUIT
(HIGH TEMPERATURE INDICATED)
2.8L " ? " SERIES (PORT)
C D
DOES " S C A N " TOOL DISPLAY MAT 145°C OR HOTTER?
NO
CODE 25 IS INTERMITTENT.
IF NO ADDITIONAL CODES WERE
STORED, REFER TO "DIAGNOSTIC
AIDS" ON FACING PAGE.
1
NO
CKT 472 SHORTED TO GROUND.
OR
CKT 472 SHORTED TO SENSOR GROUND CIRCUIT.
OR
FAULTY ECM.
YES
® DISCONNECT SENSOR.
' SCAN" SHOULD DISPLAY TEMPERATURE
BELOW-30°C.
DOES
IT?
YES
FAULTY SENSOR.
DIAGNOSTIC AID
MAT SENSOR
TEMPERATURE TO RESISTANCE VALUES
(APPROXIMATE)
°F
°C OHMS
210 100 185
160
70
450
100 38 1,800
70 20 3,400
40
4
7,500
20
-7
13,500
0 -18 25,000
-40 -40 100,700
CLEAR CODES AND CONFIRM " C L O S E D L O O P " OPERATION AND NO "SERVICE ENGINE S O O N " LIGHT.
6-17-87
©7S3190-6E