Cds G3 And Diagnostic Fault Resolution; How To Begin - Mercury V6 175 Diagnostic Manual

Maintenance Screen
The Maintenance screen displays the percentage of engine run time remaining before the next service is due. Clicking the
reset icon will return it to 100%. All PCM 112 engines are compatible with this maintenance indicator.

CDS G3 and Diagnostic Fault Resolution

How to Begin

Diagnostics is as much an art as it is a science. Diagnostic approaches vary, but a methodical approach that combines your
experience and resources will likely serve you well. Here is one possible approach.
CDS G3 is a powerful tool. Take some time to become acquainted with its operation, features, and capabilities. It will not
diagnose all problems, but will provide clues as to what is happening with a Mercury engine.
1. Talk to the customer to get as much information as possible about the complaint. There's a reason the boat was brought in.
Did a fault message appear or an alarm sound? When did the problem first start? At what speeds or power ranges does it
occur? Were there any recent changes made to the boat, its electrical system, or its use? (A new propeller or sound
system can impact the operation of a boat.) Was fuel recently added? (Stale fuel or fuel with alcohol separation can cause
problems that are difficult to pick up with a diagnostic tool.)
2. If possible, verify the symptom while the customer is present.
3. Take note of any faults that were reported by the customer.
4.
Perform a brief visual inspection. Refer to Visual/Physical Check.
5. Connect the CDS G3 tool, choose the right eBOM, and download all updates.
6. Scan the PCM and other modules for faults.
7. If no active faults are present and none are shown in Freeze Frame, CDS G3 still has various diagnostic tests available,
and examining Live Data can provide important clues. Refer to the Live Data screen while the engine is running to ensure
that sensors and actuators are behaving as expected. Refer to the Diagnostics screen for available interactive tests.
8. It is important to note that CDS G3:
a.
Does not indicate low fuel pressure. (Refer to Section 1B for an explanation of system theory.) The PCM assumes
that the pressure in the fuel rail is held at the specified pressure. If CDS G3 indicates a lean running engine, and the
fuel injectors appear to be working, verify that the pressure in the fuel rail is within specifications.
b. Does not detect poor fuel. As blended fuel ages, the alcohol and gasoline may separate and allow water to be
introduced. The PCM will try to compensate for poor fuel by keeping the fuel injectors open longer. If it tries to add too
much fuel, it will trigger a fault. Even if it does not trigger a fault, bad fuel can result in a poor‑running engine. A small
tank of known good fuel can be an important diagnostic tool.
c. Cannot determine the mechanical health of the engine. Always confirm the health of the cylinders by performing a
leakdown test after confirming that all cylinders are receiving fuel and spark. Refer to the appropriate engine service
manual.
9. If faults are present:
• Fix any active faults first. Start where the air enters the engine and work toward the exhaust. Addressing faults in this
order can save time, since a problem early in the process can lead to faults further in the process.
• Fix inactive faults second.
90-8M0146617 eng JULY 2018
Troubleshooting with the Computer Diagnostic System (CDS G3)
Maintenance screen
© 2018 Mercury Marine
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