Mercury V6 175 Diagnostic Manual page 43

NOTE: While monitoring in CDS G3, in some situations the display may show closed‑loop, when the engine is actually in
open‑loop. An engine is truly operating in closed‑loop when the UEGO1phi Live Data item is a value other than 0.98.
The PCM will then compare the targeted equivalency ratio (phi) to the actual ratio for the engine, and adjust fuel accordingly.
The amount being changed is shown in the O2Control_ITermPort/Port. This value is a multiplier. An ITerm of 0.02 is adding 2%
fuel.
In this CDS G3 screen capture, the engine has entered closed-loop control. It is targeting a phi (equivalency ratio) of 1.1484.
It is reading a phi of 1.14 and adjusting port fuel trim (02Control_Iterm_Port) by 1.86%.
The fuel injector pulse width times reflect that all cylinders are adjusted equally, rather than across banks of cylinders. Note
that eight cylinders are shown even for a six-cylinder engine; only the first six are relevant.
O2 Control State Diagnostic Aids
There are a number of items that could cause the fuel system monitoring diagnostic to fail. Check the following conditions if a
fuel system monitoring fault has occurred.
• Check fuel pressure in the rails.
• Check the power and ground connections.
• Check the fuel quality. Use a tank of known good fuel.
• Check the O2 sensor.
• Check the fuel injectors and connectors.
• Check the spark plug leads and coils.
• Check for leaks in the intake system.
• Check for exhaust leaks.
• Check the MAP sensor.
Recommended Course of Action
Step
Connect CDS G3, select the correct eBOM and
module, and download all available updates. Record
1
Freeze Frame data using the Print Screen function
or Record Data. Are these steps complete?
O2 sensor faults may be triggered by primary faults,
such as a failed sensor or actuator, battery or
sensor power high or low, or range high or low limits
2 (low oil pressure, high engine coolant temperature,
etc.).
Check for and resolve any primary faults. Did you
find and resolve any primary faults?
90-8M0146617 eng JULY 2018
Action
PCM 112 and Engine Control Overview
Yes
Go to step 2.
Go to step 8.
© 2018 Mercury Marine
67641
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No
An update to software may
have addressed a known
issue. Make sure you are
using the most current
software for CDS G3 and the
PCM.
Go to the next step.
Page 2B-3