Mercury MerCruiser MCM 454 Mag MPI Service Manual page 649

GENERAL SYSTEM DIAGNOSTICS
On-Board Diagnostic (OBD) System Check (Scan)
Step
1
2
3
4
5
6
7
Index
Page 5E-56
Downloaded from https://needmanual.com/
Action
1. Ignition "ON," engine "OFF."
2. Install Marine
Trouble Code (MDTC) tool and
switch it to "Normal Mode."
3. Observe the Malfunction Indica-
tor Lamp (MIL).
Is the MIL "ON"?
1. Ignition "OFF."
2. Install a scan tool.
3. Ignition "ON."
4. Attempt to display ECM data
with the scan tool.
Does The Scan Tool Display ECM
Data?
Attempt to start the engine.
Did The Engine Start
Continue To Run?
Select "Display DTCs" with the scan
tool.
Are Any Trouble Codes Stored?
Compare ECM data
displayed on the scan tool to the
typical scan tool data values page.
Are The Displayed Values Normal
Or Close To The Typical Values?
1. Ignition "OFF."
2. Disconnect the ECM.
3. Check the serial data CKT 461
for an open, short to ground, or
short to voltage. Also, check the
DLC battery feed circuit for an
open or short to ground and the
DLC ground CKT 450 for an
open.
4. If a problem is found, repair as
necessary.
Was A Problem Found?
Replace the ECM.
Is Action Complete?
Value(s)
Diagnostic
-
Go to Step 2 Go to Chart A-1
-
Go to Step 3
-
And
Go to Step 4 Go to Chart A-3
-
values
-
-
Repeat OBD
Repeat OBD
-
SERVICE MANUAL NUMBER 23
Yes No
Go to Step 7
Go to
applicable
Go to Step 5
DTC Chart
Refer to
"Trouble-
Refer to
shooting"
"Diagnostic
section
Testing"
System
Go to Step 7
Check
System
-
Check
90-861326--1 MARCH 1999