Toyota COMPUTER-CONTROLLED SYSTEM Training Manual page 160

TROUBLESHOOTING - Pre-diagnostic Questionin g
PRE-DIAGNOSTIC QUESTIONING (PDQ )
When carrying out troubleshooting, it is impor- • Who noticed the problem ?
tant that the technician remember to confirm the - With whom the problem most commonly
symptoms of the problem accurately and objec- occur s
tively, without preconceptions . (This means, for
• What?
example, not to just guess about the cause o f
the problem, no matter how much experience - Vehicle mode
l
- System in which problem has occurred
the technician is basing his judgement on, but t o
carry out the troubleshooting step by step, ac- • When?
cording to the directions given here .)
- Date(s)
No matter how experienced the technician, if -Time(s)
troubleshooting is attempted before the - Frequency of occurrence
symptoms have been confirmed, repairs will fai l
or a mistaken judgment will lead to the wrong
• Where 7
repairs being performed
. - Type of road/terrai n
As long as the symptoms of the problem are • How? Under what conditions?
manifesting themselves at the time the vehicle - Engine running conditions
is brought into the service shop, they can be - Driving conditions
confirmed right away . However, when the - Weathe r
symptoms fail to manifest themselves, the • Why
did customer bring vehicle in?
technician must deliberately try to reproduce
- Symptoms
them . For example, a problem that occurs onl y
when the vehicle is cold or the occurrence of A sample of a PDQ Checksheet is shown on the
vibration from the road surface during driving following page .
cannot be confirmed when the engine is warmed
up or while the vehicle is sitting still, because
the conditions under which the trouble occurred
cannot be reproduced under such circumstances .
Therefore, when attempting to ascertain what
the symptoms are, it is extremely important to
ask the customer about the problem and the
conditions under which they occurred .
IMPORTANT POINTS IN PD Q
The six items shown below are especially impor-
tant points to remember when carrying out Pre-
diagnostic Questioning .
Information on past problems (even if they are
thought to be unrelated to the present problem)
and the repair history of the vehicle will also
help in many cases, so as much information as
possible should be gathered and its relationship
with the symptoms should be correctly
asce rt ained for reference in troubleshooting .
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