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Nissan service manuals list several
checks which should be made before
reading trouble codes. Problems in the
areas listed below can cause the
computer to set false or misleading
codes. Ignoring these checks can make
you miss the real cause of a code! This
can lead to the unnecessary replace-
ment of good parts. Service manual
procedures for troubleshooting a code
assume all preliminary checks are good.
These checks vary with vehicle. Typical
checks are listed below. Refer to service
manual for your vehicle requirements.
• Visually inspect electrical wiring and
connectors.
• Visually inspect vacuum hoses and
connectors.
• Perform a compression test.
• Perform an exhaust system
backpressure test.
• Perform a fuel pressure test.
• Check curb idle speed.
• Check ignition timing.
• Check computer control of air/fuel
mixture.
• Check the idle speed switch.
• Perform a Mode 5 check, while test
driving the vehicle.
68
1) Turn the ignition
switch ON, but do
not start the
engine.
2) Turn the Diagnosis
Mode Selector ON.
3) Observe the RED
and GREEN LED's.
4) Both LED's will
flash sequentially 1 through 5 (1
flash = Mode 1, 2 flashes = Mode 2,
etc.).
5) When Mode 3 (Trouble
Codes) has been
reached, as indicated
by 3 flashes, immedi-
ately turn the Diagno-
sis Mode Selector OFF.
6) Have your pencil and paper ready.
7) Write down all displayed Trouble
Codes.
8) This completes
trouble code
retrieval on these
vehicles. Turn the
Diagnosis Mode
Selector switch
OFF, and the ignition switch to the
OFF position. (The computer will
automatically return to normal
operation.)
OFF
ON
OFF
ON
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