Emission Control Fault Indicators; Diagnostic Roadmap - Mercury MerCruiser Service Manual

Troubleshooting
11. Unplug and inspect as many of the sensors and actuators as possible. Look for signs of tampering, corrosion, damage to
the pin locking mechanisms, melted insulation, and any other evidence of shorts or other damage. Based on the results of
this inspection, further inspection of the harness may be necessary. Remember that there are many internal splices in the
harness that may be damaged or defective. If there is damage at the external connections, you will have to inspect several
of the internal splices to verify that the damage is not also present at these locations.
12. Check for adequate secondary spark. If an air gap tester is used, ensure it will not ignite any fuel vapors that may be
present in the bilge. A KV meter can also be used to check for adequate secondary voltage. Ensure that the secondary
wires are in good condition (correctly routed and that the boots are not split at either end).
IMPORTANT: The pins in the PCM connectors are delicate. Disconnect the PCM to inspect the pins only if there is reason
to suspect that the pins may be damaged.
13. Unplug and inspect the PCM connectors. Ensure that there are no bent PCM pins and that all of the correct pins are
present. Look for signs of tampering, corrosion, damage to the pin locking mechanisms, melted insulation, and any other
evidence of shorts or other damage.

Emission Control Fault Indicators

Depending on the application, engines with emissions control can inform the operator of a fault with the system in one of
several ways:
• A warning horn that will sound for five seconds and repeat at one‑half‑second intervals for 60 seconds.
• An OBD‑M malfunction indicator lamp (MIL), a stand‑alone indicator that illuminates while the OBD‑M fault is active.
• An engine icon incorporated into another display, such as VesselView or SmartCraft, which may be accompanied by an
audible alarm.
Early engines were not equipped with OBD‑M MILs. Update kits are available for those who wish to purchase this feature.

Diagnostic Roadmap

This is your starting point for diagnosing an emissions controlled engine. Start with step 1, answer the question and proceed
accordingly. Do not skip any step, as each step depends on the results of previous steps to ensure success. You may be
directed to other sections in this manual or to a different manual entirely.
Step Question
Does the engine system power up
1 when the key switch is turned to the
run position?
Does the CDS G3 service tool
2
communicate with the PCM?
Does the engine crankshaft rotate
3 when you attempt to start the
engine?
Does the engine start and continue
4
to run?
5 Does the engine start hard?
Does the engine stall when
6 attempting to idle, or run so poorly
it is unusable?
Does the engine start and continue
to run with the warning horn or
7
engine gauges indicating an active
diagnostic fault?
Can you tell that the engine is not
running properly by sight, sound,
8 smell, or touch? Do you observe a
symptom, yet there are no
diagnostic faults?
Page 1D-4
Technical Details
The warning horn completes a self‑test. The
engine gauges power up. If present, the
OBD‑M system completes a self‑test.
CDS G3 must display PCM data on the
module data screen.
The engine must rotate at least 50 RPM
before a crankshaft sensor signal will be
seen.
If the engine starts and immediately dies,
your answer must be no.
The engine starts, but not readily. It may or
may not stall.
It is difficult or impossible to use the engine
to maneuver the boat. The engine does not
respond to shift and throttle commands as
expected.
The engine may or may not run normally,
but it keeps running without difficulty. There
is at least one diagnostic fault. The OBD‑M
lamp or engine icon may be on or off.
The engine gauges do not indicate any
diagnostic faults. The warning horn is silent.
The OBD‑M lamp or engine icon may be on
or off. The PCM does not detect any
problems, yet the engine has a problem.
© 2016 Mercury Marine
Yes
Go to step 2. Go to Chart R1.
Refer to CDS G3
Go to step 3.
Service Tool.
Go to step 4. Go to Chart R3.
Go to step 5. Go to Chart R4.
Go to Chart R5. Go to step 6.
Go to step 7.
Go to Chart R6.
Refer to the PCM
Go to step 8.
112 Service
Manual.
The problem has
been resolved or is
Refer to
not presenting itself
Diagnosis by
at this time.
Symptom.
Diagnosis is
complete.
90-8M0099748 eng DECEMBER 2015
No