Mercury 305 CID - Page 634

ELECTRONIC FUEL INJECTION (MULTI-PORT AND THROTTLE BODY) - 5E-9390-823225--1 1096
Code 33: MAP Circuit (Non-Scan)
(2 of 2)
CONNECT DVM
BETWEEN HARNESS
TERMINAL “B” AND
ENGINE GROUND.
IS VOLTAGE OVER 4
VOLTS?
YES
YES NO
NO
FAULTY CONNECTION AT ECM
OR
CKT 416 OPEN
OR
SHORTED TO GROUND
OR
FAULTY ECM.
YES
CKT 432
SHORTED
TO VOLTAGE.
OPEN CKT 432
OR
FAULTY
CONNECTION
AT ECM
OR
FAULTY ECM.
1
3
• IGNITION “OFF.”
• CONNECT A TEST LIGHT TO
BATTERY POSITIVE B+.
• TOUCH TEST LIGHT TO HARNESS
TERMINAL “B” (MAP SENSOR
SIGNAL). IS TEST LIGHT “ON”?
• IGNITION “OFF.”
• DISCONNECT VACUUM PLUG LOCATED UNDER
PLENUM AT FRONT AND INSTALL A VACUUM
GAUGE IN THE VACUUM PORT.
• START ENGINE AND RAISE RPM TO ABOUT 1000
RPM. VACUUM GAUGE READING SHOULD BE 14in.
Hg (45.5 kPa) OR MORE AND STEADY. IS IT?
REPAIR LOW OR UNSTEADY
VACUUM PROBLEM.
2
NOYES NO
• DISCONNECT ECM.
• TOUCH TEST LIGHT
CONNECTED TO
BATTERY POSITIVE
B+ TO HARNESS
TERMINAL “B”.
IS TEST LIGHT
“ON”? SEE NOTE
MAP
SENSOR
FAULTY.
NO
CKT 432 SHORTED
TO GROUND.
FAULTY ECM.
• IGNITION “OFF.”
• REMOVE VACUUM GAUGE AND REINSTALL VACUUM
PLUG IN VACUUM PORT.
• DISCONNECT MAP SENSOR ELECTRICAL CONNECTOR.
• IGNITION “ON.”
• CONNECT A DVM FROM HARNESS TERMINAL “C” (CKT
416, 5 VOLT REFERENCE) TO HARNESS TERMINAL “A”
(CKT 814, SENSOR GROUND).
IS VOLTAGE READING OVER 4 VOLTS?
YES NO
• CONNECT DVM FROM MAP SENSOR HARNESS
TERMINAL “C” TO A GOOD GROUND ON ENGINE.
IS VOLTAGE OVER 4 VOLTS?
• CONNECT DVM FROM HARNESS TERMINAL “C”
(CKT 416) TO HARNESS TERMINAL “B” (MAP
SENSOR SIGNAL, CKT 432).
IS VOLTAGE READING OVER 4 VOLTS?
FAULTY CONNECTION
AT ECM
OR
CKT 814 OPEN
OR
FAULTY ECM.
YES
NO
45
6
NOTE: USING A TEST LIGHT WITH 100 mA OR LESS RATING MAY
SHOW A FAINT GLOW WHEN TEST ACTUALLY STATES NO LIGHT.