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Honda 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 &
connectors.
• Visually inspect vacuum hoses &
connectors.
• Perform a compression test.
• Perform an exhaust system
backpressure test.
• Perform a fuel pressure test.
• Check curb idle speed.
• Check ignition timing.
1) Make sure the engine computer
LED display is easily viewable.
2) Have your pencil and paper ready.
3) Turn the
ignition
switch ON,
but DO NOT
START THE
ENGINE.
4) Get code numbers from the LED
display.
8
4
2
32
= ON
1
= OFF
Example of code zero:
No LED's are lit,
indicating a code
zero ("0").
Example of code 2:
LED 2 is lit,
indicating a code 2.
Example of code 10:
LED's 8 and 2 are lit,
indicating a code 10.
(8 + 2 = 10)
Each LED has a
numeric value.
• The left LED has a
value of 8.
• The next LED in line
has a value of 4.
• The next LED in line
has a value of 2.
• The right LED has a
value of 1.
Add values of the
lighted LED's to get
the Trouble Code.
(Off LED's have a
value of zero.)
8
4
2
8
4
2
8
4
2
1
1
1
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