Toyota COMPUTER-CONTROLLED SYSTEM Training Manual page 171

SYMPTOM SIMULATIO N
SYMPTOM SIMULATIO N
The most difficult problems in troubleshooting
are intermittent problems : that is, problems
about which the customer has a complaint, but
which do not occur or cannot be comfirmed in
the service shop . Intermittent problems often
include complaints about the "CHECK ENGINE"
lamp going on and off erratically .
To ensure accurate diagnosis of such problems,
ask the customer to provide as much information
as possible .
To do this, question the customer closely about
the problem, using the Pre-diagnostic
Questioning Checksheet, then try to reproduce
the problem on the customer's vehicle .
The symptom simulation methods (applying
vibration, heat, or humidity) described below are
effective ways of reproducing the symptoms for
problems of this nature .
OBJECTIVE To learn how to reproduce intermi tt ent problems
PREPARATIO N
APPLICABLE ENGIN E
1
Terminals have sprea d
VIBRATION METHOD : When vibration seems to be the major cause .
CONNECTORS
Gently shake the connectors vertically and hori-
zontally and pull on them :
(a) Are they loose ?
(b) Does the wire harness have enough slack ?
Watch especially for :
• Dirty terminal s
• Loose contact due to spreading of terminals
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