Troubleshooting Without A Computer Diagnostic System (Cds); Troubleshooting With The Computer Diagnostic System (Cds); Accessing Ecm Information With The Cds - Mercury 25 EFI Service Manual

Ignition

Troubleshooting without a Computer Diagnostic System (CDS)

Troubleshooting without the computer diagnostic system (CDS) is limited to checking resistance on some of the sensors.
Typical failures usually do not involve the PCM. Connectors, set‑up, and mechanical wear are most likely at fault.
• Verify the ignition coils are securely installed (pushed in) into the spark plugs.
• The engine may not run or may not run above idle with the wrong spark plugs installed.
• Swap ignition coils to see if the problem follows the coil or stays with the particular cylinder.
IMPORTANT: Disconnecting a sensor while the engine is running may result in a fault recording in the PCM Fault History. Use
the CDS to view the PCM fault history when troubleshooting/repair is completed.
• If all cylinders exhibit similar symptoms, the problem is with a sensor or harness input to the PCM.
• If problem is speed related or intermittent, it is probably connector or contact related. Inspect connectors for corrosion,
loose wires, or pins pushed back into connector. Verify the connectors are properly seated.
• Inspect the harness for damage: pinched or cut wires and chafing.
• Secure the grounds and all connections involving ring terminals. Apply Liquid Neoprene to all ring terminal connections.
Tube Ref No.
Liquid Neoprene
25
• Inspect the fuel pump harness connector for corrosion, loose wires, or pins pushed back into connector.
• Check the fuel pump pressure.

Troubleshooting with the Computer Diagnostic System (CDS)

The ECM is designed that if a sensor fails, the ECM will compensate so that the engine does not go into an over‑rich condition.
Because of this, disconnecting a sensor for troubleshooting purposes may have no noticeable effect.
The CDS has been developed specifically to help technicians diagnose and repair Mercury Marine 2 and 4 cycle engines.
CDS G3 Diagnostic Tool Kit
Attach the 84‑899150T01 diagnostic cable to the ECM diagnostic port and attach the 84‑822560A7 adapter to the
84‑899150T01 diagnostic cable. The CDS will monitor sensors and ECM data values including status switches. The ECM
program can help diagnose intermittent engine problems. It can record the state of the engine sensors and switches for a
period of up to 10 minutes, which then can be played back and analyzed.
a
Adapter Harness
Adapter Harness
When using the CDS for troubleshooting, follow the CDS driven troubleshooting menu for the complete diagnostic
troubleshooting procedures.

Accessing ECM Information with the CDS

The CDS allows the technician to specifically identify the engine to be tested. It is important to accurately identify the engine
because in many cases, the available testing options depend on the engine identified. It is also capable of storing customer
contact information and will identify the required diagnostic cables for the engine selected.
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Description
© 2016 Mercury Marine
Where Used
All ring terminal connections
8M0114141
a - Diagnostic port
b
b - ECM
23249
84‑899150T01
84‑822560A7
Part No.
92- 25711 3
90-8M0105568 eng MARCH 2016