IN05Y±22
± INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMSIN±29
29 Author: Date:
2001 PRIUS (RM778U)
HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS
GENERAL INFORMATION
A large number of ECU controlled systems are used in the PRIUS. In general, the ECU controlled system
is considered to be a very intricate system requiring a high level of technical knowledge and expert skill to
troubleshoot. However, the fact is that if you proceed to inspect the circuits one by one, troubleshooting of
these systems is not complex. If you have adequate understanding of the system and a basic knowledge
of electricity, accurate diagnosis and necessary repair can be performed to locate and fix the problem. This
manual is designed through emphasis of the above standpoint to help service technicians perform accurate
and effective troubleshooting, and is compiled for the following major ECU controlled systems:
The troubleshooting procedure and how to make use of it are described on the following pages.
SystemPage
6. EngineDI±1
7. Hybrid Vehicle Control SystemDI±174
8. HV Battery Control SystemDI±312
9. Anti±Lock Brake System With EBD & RBSDI±351
10.Electric Motor Power SteeringDI±452
11. Supplemental Restraint SystemDI±495
12.Cruise Control SystemDI±640
13.Combination Meter SystemDI±662
14.Body Control SystemDI±678
15.Driver Door Control SystemDI±730
16.Multiplex Communication SystemDI±750
17.Navigation SystemDI±789
18.Air Conditioning SystemDI±864
FOR USING OBD II SCAN TOOL OR TOYOTA HAND±HELD TESTER
Before using the scan tool or tester, the scan tool's instruction book or tester's operator manual should
be read thoroughly.
If the scan tool or tester cannot communicate with ECU controlled systems when you have connected
the cable of the scan tool or tester to DLC3, turned the ignition switch ON and operated the scan tool,
there is a problem on the vehicle side or tool side.
(1) If communication is normal when the tool is connected to another vehicle, inspect the diagnosis
data link line (Busline) or ECU power circuit of the vehicle.
(2) If communication is still not possible when the tool is connected to another vehicle, the problem
is probably in the tool itself, so perform the Self Test procedures outline in the Tester Operator's
Manual.
