Toyota AVENSIS 1999 Supplement Manual page 34

– HOW TO TROUBLESHOOT ECU CONTROLLED
INTRODUCTION
SYSTEMS
HOW TO USE THE DIAGNOSTIC
CHART AND INSPECTION
PROCEDURE
1. CONNECTOR CONNECTION AND TERMINAL IN-
SPECTION
For troubleshooting, diagnostic trouble code charts or
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problem symptom charts are provided for each circuit with
detailed inspection procedures on the following pages.
FI0046
When all the component parts, wire harnesses and con-
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nectors of each circuit except the ECU are found to be
normal in troubleshooting, then it is determined that the
problem is in the ECU. Accordingly, if diagnosis is per-
formed without the problem symptoms occurring, refer to
Step 8 to replace the ECU. So always confirm that the
problem symptoms are occurring, or proceed with inspec-
tion while using the symptom simulation method.
The instructions "Check wire harness and connector" and
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"Check and replace ECU" which appear in the inspection
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procedure, are common and applicable to all diagnostic
trouble codes. Follow the procedure outlined below
whenever these instructions appear.
OPEN CIRCUIT:
This could be due to a disconnected wire harness, faulty con-
tact in the connector, and a connector terminal pulled out, etc.
HINT:
It is rarely the case that a wire is broken in the middle of
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it. Most cases occur at the connector. In particular, care-
fully check the connectors of sensors and actuators
FI0048
Faulty contact could be due to rusting of the connector
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terminals, to foreign materials entering terminals or a de-
formation of connector terminals. Simply disconnecting
and reconnecting the connectors once changes the
condition of the connection and may result in a return to
normal operation. Therefore, in troubleshooting, if no ab-
normality is found in the wire harness and connector
check, but the problem disappears after the check, then
the cause is considered to be in the wire harness or con-
nectors.
SHORT CIRCUIT:
This could be due to a contact between wire harness and the
body ground or to a short circuit occurred inside the switch, etc.
HINT:
When there is a short between the wire harness and body
ground, check thoroughly whether the wire harness is caught
in the body or is clamped properly.
IN–29
IN011–03