Mercury MERCRUISER, Service Manual, Page: 80 / 566

Step Diagnostic Process Details Yes No
9
Using the scan tool, display the ECT
sensor temperature and record the
value.
Check the resistance of the ECT
sensor.
Compare the approximate temperature
of the ECT sensor to an accurate
reading of ambient air temperature.
Is the ECT sensor temperature near
the resistance temperature?
Refer to
PCM 112–Section 3A
‑
Component testing
..
Go to step 10.
Retest the system.
Locate and repair
high‑resistance or poor
connection in the ECT
signal circuit or the ECT
sensor ground.
10
Check for intermittent opens or shorts
to ground in the MAP sensor circuit.
Was a problem found?
Wiggle the MAP sensor
harness while monitoring data
on the CDS G3.
Locate and repair the
open in the harness.
Go to step 11.
11
Using the scan tool, check for proper
operation of the TPS.
Was a problem
found?
–
Locate and repair the
problem with the TPS.
Retest the system.
Go to step 12.
12
Check for engine mechanical
problems.
Was a problem found?
Check for the following:
• Low compression
• Leaking cylinder head
gaskets
• Worn camshaft
• Improper valve timing or
valve train problem
• Restricted exhaust system
Refer to
Section 3
‑
Engine Mechanical
.
Go to step 13.
13
Review all of the procedures in this table. If all procedures have been completed and no problem found, inspect the
following:
• CDS G3 scan tool data
• All of the electrical connections within a suspect circuit or system
NOTE: The crankshaft position sensor (CPS) is an exception. It will
not
set a fault if it fails completely.
Chart R6: Engine Stalls
This procedure is intended to diagnose a PCM 112 mechanical shift engine that starts without difficulty, but stalls while
attempting to idle or runs so poorly as to be unusable. You are here because you answered yes to step 6 of the diagnostic
roadmap.
Step Diagnostic Process Details Yes No
1
Connect a known good fuel source in
place of the boat's fuel tank.
Does the engine still stall?
– Go to step 2.
The problem is with
the boat fuel supply.
2
Inspect the fuel filter.
Is the fuel filter obstructed?
–
Clean or replace the fuel filter.
Test the fuel for contaminants.
Go to step 3.
3
Check the fuel pressure.
Is the fuel pressure steady?
– Go to step 4. Go to
Chart T3
.
4
Check the ground wires for loose
connections or corrosion.
Were problems found?
–
Correct the problems and
retest the engine.
Go to step 5.
5
Check for mechanical engine problems.
Were problems found?
Check for the following:
• Low compression
• Worn camshaft
• Restricted intake or
exhaust system
Correct the problems and
retest the engine.
Contact Mercury
Product Support.
Troubleshooting
Page 1D-10 © 2016 Mercury Marine 90-8M0099748 eng DECEMBER 2015