technical data TOYOTA SIENNA 2007 Service Repair Manual

IN–30INTRODUCTION – HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS
IN
HOW TO TROUBLESHOOT ECU
CONTROLLED SYSTEMS
GENERAL INFORMATION
A large number of ECU controlled systems are used in the
SIENNA. In general, ECU controlled systems are considered
to be very intricate, requiring a high level of technical
knowledge to troubleshoot. However, most problem checking
procedures only involve inspecting the ECU controlled
system's circuits one by one. An adequate understanding of
the system and a basic knowledge of electricity is enough to
perform effective troubleshooting, accurate diagnoses and
necessary repairs.
FOR USING INTELLIGENT TESTER
– Before using the intelligent tester, read the tester
operator's manual thoroughly.
– If the tester cannot communicate with the ECU controlled
systems when the tester is connected to the DLC3 with the
ignition switch on and the tester turned on, there is a
problem on the vehicle side or tester side.
(1) If communication is normal when the tester is
connected to another vehicle, inspect the diagnosis
data link line (Bus (+) line) or ECU power circuit of the
vehicle.
(2) If communication is still not possible when the tester is
connected to another vehicle, the problem is probably
in the tester itself. Perform the Self Test procedures
outlined in the tester operator's manual.