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Troubleshooting
CODE READER TROUBLESHOOTING GUIDE
75 Chapter 5
CODE READER TROUBLESHOOTING GUIDE
If all procedures are followed and the Code Reader will not
retrieve codes when performing the Key On Engine Off
(KOEO) Self Test, check the following:
1. Code Reader's batteries, change batteries as required.
2. Check the vehicles Test Connector pins for corrosion and
clean as necessary.
NOTE:
The Code Reader receives a ground signal from one of
the pins of the vehicle's Test Connectors and uses it to signal
the computer to initiate the Self-Tests. A problem in the
vehicle's Test Connector ground pin or circuit will result in an
improper ground being supplied to the code reader which will
effect the code reader's ability to signal the computer to initiate
the Self Test. If after performing the procedures in step one and
two, the code reader still does not work proceed to EEC-IV
Systems/ MCU Systems bellow (as applicable).
EEC-IV Systems (most 1985-95 vehicles)
On some vehicles equipped with the EEC-IV Computer
Systems the vehicle's Test Connector ground circuit may have
a poor ground due to bad ground point connections, old and
corroded wiring, poor connector to wire contacts etc. that will
prevent the Code Reader from initiating the Self-Test. To
alleviate this problem and allow the Code Reader to initiate
the Self-Test, perform the following steps.
1. Disconnect the single pin
Vehicle's Test Connector from
the code reader (leave the six
pin Test Connector connected
to code reader).
2. Route a jumper wire from the
vehicle's harness single pin
Test Connector to the
vehicle's battery negative post
or to a clean spot in the
vehicle's metal frame. See
drawing.
3. Proceed with KOEO Self Test as per KOEO instructions.
MEMORY
ON / OFF
TEST / HOLD
+
-
5
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