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INTRODUCTION – HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMSIN–35
IN
(a) First, check the ECU ground circuit. If it is faulty,
repair it. If it is normal, the ECU could be faulty.
Temporarily replace the ECU with a normally
functioning one and check if the symptoms occur. If
the trouble symptoms disappear, replace the
original ECU.
(1) Measure the resistance between the ECU
ground terminal and body ground.
Standard resistance:
Below 1
(2) Disconnect the ECU connector. Check the
ground terminal on the ECU side and wire
harness side for bending, corrosion or foreign
matter. Lastly, check the contact pressure of the
female terminals.
IN00383E02
IN00384E03
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IN–36INTRODUCTION – HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS
IN
HOW TO PROCEED WITH
TROUBLESHOOTING
1. OPERATION FLOW
HINT:
Perform troubleshooting in accordance with the
procedures below. The following is an outline of basic
troubleshooting procedures. Confirm the troubleshooting
procedures for the circuit you are working on before
beginning troubleshooting.
NEXT
(a) Ask the customer about the conditions and environment
when the problem occurred.
NEXT
Standard voltage:
11 to 14 V
If the voltage is below 11 V, recharge or replace the
battery before proceeding.
NEXT
(a) Visually check the wire harnesses, connectors and fuses
for open and short circuits.
(b) Warm up the engine to the normal operating
temperature.
(c) Confirm the problem symptoms and conditions, and
check for DTCs
Result
B
A
1VEHICLE BROUGHT TO WORKSHOP
2CUSTOMER PROBLEM ANALYSIS
3INSPECT BATTERY VOLTAGE
4SYMPTOM CONFIRMATION AND DTC (AND FREEZE FRAME DATA) CHECK
Result Proceed to
DTC is output A
DTC is not output B
Go to step 6
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INTRODUCTION – HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMSIN–37
IN
(a) Check the results obtained in step 4. Then find the
output DTC in the DTC chart. Look at the "Trouble Area"
column for a list of potentially malfunctioning circuits and
/ or parts.
NEXT
(a) Check the results obtained in step 4. Then find the
problem symptoms in the problem symptoms table. Look
at the "Suspected Area" column for a list of potentially
malfunctioning circuits and / or parts.
NEXT
(a) Identify the malfunctioning circuit or part.
NEXT
(a) Adjust, repair or replace the malfunctioning circuit or
parts.
NEXT
(a) After the adjustment, repairs or replacement, confirm
that the malfunction no longer exists. If the malfunction
does not reoccur, perform a confirmation test under the
same conditions and in the same environment as when
the malfunction occurred the first time.
NEXT
2. CUSTOMER PROBLEM ANALYSIS
5DTC CHART
Go to step 7
6PROBLEM SYMPTOMS CHART
7CIRCUIT INSPECTION OR PARTS INSPECTION
8ADJUST, REPAIR OR REPLACE
9CONFIRMATION TEST
END
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IN–38INTRODUCTION – HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS
IN
HINT:
• In troubleshooting, confirm that the problem symptoms
have been accurately identified. Preconceptions should be
discarded in order to make an accurate judgment. To
clearly understand what the problem symptoms are, it is
extremely important to ask the customer about the
problem and the conditions at the time the malfunction
occurred.
• Gather as much information as possible for reference.
Past problems that seem unrelated may also help in some
cases.
• The following 5 items are important points in the problem
analysis:
3. SYMPTOM CONFIRMATION AND DIAGNOSTIC
TROUBLE CODE
HINT:
The diagnostic system in the SIENNA has various
functions.
• The first function is the Diagnostic Trouble Code
(DTC) check. A DTC is a code stored in the ECU
memory whenever a malfunction in the signal circuits
to the ECU occurs. In a DTC check, a previous
malfunction's DTC can be checked by a technician
during troubleshooting.
• Another function is the Input Signal Check, which
checks if the signals from various switches are sent to
the ECU correctly.
By using these functions, the problem areas can be
narrowed down and troubleshooting is more effective.
Diagnostic functions are incorporated in the following
system in the SIENNA.
What Vehicle model, system name
When Date, time, occurrence frequency
Where Road conditions
Under what conditions? Running conditions, driving conditions, weather conditions
How did it happen? Problem symptoms
SystemSYMPTOM CONFIRMATION AND DIAGNOSTIC TROUBLE CODE
DTC Check
(Normal Mode)DTC Check
(Check Mode)Sensor Check/
Test Mode
(Input Signal
Check)Data List Active Test
2GR-FE SFI System
X
U151E Automatic Transaxle SystemX
U151F Automatic Transaxle SystemX
Tire pressure warning systemXX
Anti-lock Brake System
X
Vehicle Stability Control SystemX
Air Conditioning System (for Manual Air
Conditioning System)XXXXX
Air Conditioning System (for Automatic Air
Conditioning System)
XX
Airbag SystemXX
Occupant Classification System
XXX
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INTRODUCTION – HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMSIN–39
IN
• In the DTC check, it is very important to determine
whether the problem indicated by the DTC either: 1)
still occurs, or 2) occurred in the past but has returned
to normal. In addition, the DTC should be compared
to the problem symptom to see if they are related. For
this reason, DTCs should be checked before and after
confirmation of symptoms (i.e., whether or not
problem symptoms exist) to determine current system
conditions, as shown in the flowchart below.
• Never skip the DTC check. Failing to check DTCs
may, depending on the case, result in unnecessary
troubleshooting for systems operating normally or
lead to repairs not related to the problem. Follow the
procedures listed in the flowchart in the correct order.
Theft Deterrent System XXXXX
Engine Immobiliser System
XX
Cruise Control SystemXXX
Dynamic Laser Cruise Control System
XXX
Lighting System
XX
Wiper and Washer SystemXXXXX
Power Door Lock Control System X X X
Wireless Door Lock Control SystemXX
Key Reminder Warning System X X XX
Meter / Gauge System X X X
Audio and Visual SystemXXXX
Rear Seat Entertainment System XXXXX
Navigation System
XXXX
Clearance Sonar SystemXXXXX
Rear View Monitor System XXXXX
Power Window Control System (with Jam
Protection Function)XXX
Power Window Control System (without Jam
Protection Function)XXXXX
Power Mirror Control System (with Memory) X X X
Power Mirror Control System (without Memory)XXXXX
Front Power Seat Control System X X X
Rear No. 2 Seat Assembly (with Power Stowing
Function)XXXXX
Window Deogger SystemXXXXX
Power Slide Door System
XX
Slide Door Closer System X X X
Back Door Closer SystemXX
Power Back Door SystemXX
Sliding Roof System XXXXX
Multiplex Communication System XXXXX
CAN Communication System XXXXXSystemSYMPTOM CONFIRMATION AND DIAGNOSTIC TROUBLE CODE
DTC Check
(Normal Mode)DTC Check
(Check Mode)Sensor Check/
Test Mode
(Input Signal
Check)Data List Active Test
Page 70 of 3000
IN–40INTRODUCTION – HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS
IN
• The following flowchart shows how to proceed with
troubleshooting using the DTC check. Directions from
the flowchart will indicate how to proceed either to
DTC troubleshooting or to the troubleshooting of each
problem symptom.
NEXT
NEXT
Result
B
A
NEXT
Result
B
A
Result
1DTC CHECK
2MAKE A NOTE OF DTCS DISPLAYED AND THEN CLEAR MEMORY
3SYMPTOM CONFIRMATION
Result Proceed to
No symptoms exist A
Symptoms exist B
Go to step 5
4SIMULATION TEST USING SYMPTOM SIMULATION METHODS
5DTC CHECK
Result Proceed to
DTC is not output A
DTC is output B
TROUBLESHOOTING OF PROBLEM
INDICATED BY DTC
6SYMPTOM CONFIRMATION
Result Proceed to
No symptoms exist A
Symptoms exist B
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INTRODUCTION – HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMSIN–41
IN
If a DTC was displayed in the initial DTC check, the
problem may have occurred in a wire harness or
connector in that circuit in the past. Check the wire
harness and connectors.
B
A
The problem still occurs in a place other than the diagnostic
circuit (the DTC displayed first is either for a past problem or
a secondary problem).
4. SYMPTOM SIMULATION
HINT:
The most difficult case in troubleshooting is when no
problem symptoms occur. In such a case, a thorough
problem analysis must be carried out. A simulation of the
same or similar conditions and environment in which the
problem occurred in the customer's vehicle should be
carried out. No matter how much skill or experience a
technician has, troubleshooting without confirming the
problem symptoms will lead to important repairs being
overlooked and mistakes or delays.
For example:
With a problem that only occurs when the engine is
cold or as a result of vibration caused by the road
during driving, the problem can never be
determined if the symptoms are being checked on
a stationary vehicle or a vehicle with a warmed-up
engine. Vibration, heat or water penetration
(moisture) is difficult to reproduce. The symptom
simulation tests below are effective substitutes for
the conditions and can be applied on a stationary
vehicle. Important points in the symptom
simulation test:
In the symptom simulation test, the problem
symptoms as well as the problem area or parts
must be confirmed. First, narrow down the
possible problem circuits according to the
symptoms. Then, connect the tester and carry out
the symptom simulation test, judging whether the
circuit being tested is defective or normal. Also,
confirm the problem symptoms at the same time.
Refer to the problem symptoms table for each
system to narrow down the possible causes.SYSTEM NORMAL
TROUBLESHOOTING OF EACH PROBLEM SYMPTOM
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IN–42INTRODUCTION – HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS
IN
(a) VIBRATION METHOD: When a malfunction seems
to occur as a result of vibration.
(1) PART AND SENSOR
Apply slight vibration with a finger to the part of
the sensor suspected to be the cause of the
problem, and check whether or not the
malfunction occurs.
NOTICE:
Applying strong vibration to relays may open
relays.
(2) CONNECTORS
Slightly shake the connector vertically and
horizontally.
(3) WIRE HARNESS
Slightly shake the wire harness vertically and
horizontally.
HINT:
The connector joint and fulcrum of the vibration
are the major areas that should be checked
thoroughly.
(b) HEAT METHOD: When a malfunction seems to
occur when the area in question is heated.
(1) Heat the component that is the possible cause of
the malfunction with a hair dryer or similar
device. Check if the malfunction occurs.
NOTICE:
• Do not heat to more than 60
C (140F).
Exceeding this temperature may damage
the components.
• Do not apply heat directly to the parts in
the ECU.
(c) WATER SPRINKLING METHOD: When a
malfunction seems to occur on a rainy day or in
high-humidity.
(1) Sprinkle water onto the vehicle and check if the
malfunction occurs.
NOTICE:
• Never sprinkle water directly into the
engine compartment. Indirectly change
the temperature and humidity by spraying
water onto the front of the radiator.
• Never apply water directly onto the
electronic components.
HINT:
If the vehicle has or had a water leakage
problem, the leakage may have damaged the
ECU or connections. Look for evidence of
corrosion or short circuits. Proceed with caution
during water tests.B071602E03
D025085E02