Mercury MerCruiser MCM 454 Mag MPI Service Manual page 695

GENERAL SYSTEM DIAGNOSTICS
Discrete Input Circuit Check - Non-Scan 7.4L MPI Only (5 of 5)
TESTING FOR OPEN CIRCUITS
STEP
1
2
3
4
NOTE: The ECM should only be replaced after all switches and circuits have been tested
and found to be functioning properly.
Index
Page 5E-102
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ACTION
1. Disconnect PUR wire from oil pressure
switch.
2. Disconnect TAN/WHT wire from gear
lube monitor.
3. Disconnect BLU/TAN wire from transmis-
sion temperature switch (if equipped).
4. Key "ON", engine "OFF".
5. One at a time, touch each wire to ground
(–) that was disconnected.
Does audio warning buzzer sound when
grounding PUR wire?
Does audio warning buzzer sound when
grounding TAN/WHT wire?
Does audio warning buzzer sound when
grounding BLU/TAN wire?
1. Key "OFF".
2. Disconnect ECM J1 connector.
3. Check for continuity between all wires
disconnected in "Step 1" and terminal J1-4
(J1-6 on Later Models).
Is there continuity on PUR wire?
Is there continuity on TAN/WHT wire?
Is there continuity on BLU/TAN wire?
Circuit(s) is not open.
Repair open circuit.
SERVICE MANUAL NUMBER 23
VALUE YES NO
PROCEED TO
Step 3 Step 2
Step 3 Step 2
Step 3 Step 2
0 Ohms Step 3 Step 4
0 Ohms Step 3 Step 4
0 Ohms Step 3 Step 4
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–
90-861326--1 MARCH 1999
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