Toyota AVENSIS 2000 Supplement Manual page 29

IN–24
3. SYMPTOM SIMULATION
The most difficult case in troubleshooting is when there are no problem symptoms occurring. In such cases,
a thorough customer problem analysis must be carried out, then simulate the same or similar conditions and
environment in which the problem occurred in the customer's vehicle. No matter how much experience a
technician has, or how skilled he or she may be, if he or she proceeds to troubleshoot without confirming
the problem symptoms he or she will tend to overlook something important in the repair operation and make
a wrong guess somewhere, which will only lead to a standstill. For example, for a problem which only occurs
when the engine is cold, or for a problem which occurs due to vibration caused by the road during driving,
etc., the problem can never be determined so long as the symptoms are confirmed with the engine hot condi-
tion or the vehicle at a standstill. Since vibration, heat or water penetration (moisture) is likely cause for prob-
lem which is difficult to reproduce, the symptom simulation tests introduced here are effective measures in
that the external causes are applied to the vehicle in a stopped condition.
Important Points in the Symptom Simulation Test:
In the symptom simulation test, the problem symptoms should of course be confirmed, but the problem area
or parts must also be found out. To do this, narrow down the possible problem circuits according to the symp-
toms before starting this test and connect a tester beforehand. After that, carry out the symptom simulation
test, judging whether the circuit being tested is defective or normal and also confirming the problem symp-
toms at the same time. Refer to the problem symptoms table for each system to narrow down the possible
causes of the symptom.
1 VIBRATION METHOD: When vibration seems to be the major cause.
CONNECTORS
Slightly shake the connector vertically and horizontally.
WIRE HARNESS
Slightly shake the wire harness vertically and horizontally.
The connector joint, fulcrum of the vibration, and body
through portion are the major areas to be checked thorough-
ly.
PARTS AND SENSOR
Apply slight vibration with a finger to the part of the sensor
considered to be the problem cause and check that the mal-
function occurs.
HINT:
Applying strong vibration to relays may result in open relays.
AVENSIS/CORONA SUP (RM781E)
INTRODUCTION – HOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS
Shake Slightly
Swing Slightly
Vibrate Slightly
V07268