INTRODUCTION: HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS: HOW TO PROCEED WITH TROUBLESHOOTING; 2018 - 2020 MY Sienna [11/2017

Perform troubleshooting in accordance with the procedure below. The following is an outline of basic troubleshooting procedure. Confirm the troubleshooting procedure for the circuit you are working on before beginning troubleshooting.

(a) Ask the customer about the conditions and environment when the problem occurred.

If the voltage is below 11 V, recharge or replace the battery before proceeding to the next step.

(a) Visually check the wire harnesses, connectors and fuses for open and short circuits.

Result

(a) Find the output DTC in the DTC chart. Look at the Trouble Area column for a list of potentially malfunctioning circuits and/or parts.

Result

(a) 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.

(a) After the adjustment, repairs or replacement of components, confirm that the malfunction no longer exists. If the malfunction does not recur, perform a confirmation test under the same conditions and in the same environment as when the malfunction first occurred.

HINT:

When 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 for problem analysis:

What	Vehicle model, system name
When	Date, time, occurrence frequency
Where	Road conditions
Under what conditions?	Driving conditions, weather conditions
How did it happen?	Problem symptoms

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 can be more effective. Diagnostic functions are incorporated in the following systems of this vehicle.

System	DTC Check (Normal Mode)	DTC Check (Check Mode)	Freeze-frame Data	Sensor Check/Test Mode (Input Signal Check)	Data List	Active Test	Customize Parameter
2GR-FKS SFI SYSTEM	○	○	○	-	○	○	-
CRUISE CONTROL SYSTEM	○	-	○	-	○	○	-
DYNAMIC RADAR CRUISE CONTROL SYSTEM	○	-	○	-	○	○	-
FORWARD RECOGNITION CAMERA SYSTEM	○	-	○	-	○	○	-
LANE DEPARTURE ALERT SYSTEM (w/ Steering Control)	○	-	○	-	○	○	○
UA80E AUTOMATIC TRANSAXLE SYSTEM	○	○	○	-	○	○	-
UA80F AUTOMATIC TRANSAXLE SYSTEM	○	○	○	-	○	○	-
ACTIVE TORQUE CONTROL 4WD SYSTEM	○	-	-	○	○	○	-
TIRE PRESSURE WARNING SYSTEM	○	-	-	○	○	○	-
VEHICLE STABILITY CONTROL SYSTEM	○	-	○	○	○	○	-
POWER STEERING SYSTEM	○	-	○	-	○	-	-
STEERING LOCK SYSTEM	○	-	-	-	○	○	-
HEATED STEERING WHEEL SYSTEM	-	-	-	-	-	-	-
AUDIO AND VISUAL SYSTEM	○	-	-	-	○	○	-
REAR SEAT ENTERTAINMENT SYSTEM	○	-	-	-	-	-	-
NAVIGATION SYSTEM	○	-	-	-	○	○	-
INTUITIVE PARKING ASSIST SYSTEM	○	-	-	-	○	○	○
PARKING ASSIST MONITOR SYSTEM	○	-	-	-	○	-	-
REAR VIEW MONITOR SYSTEM	○	-	-	-	-	-	-
BLIND SPOT MONITOR SYSTEM	○	-	○	-	○	-	-
PANORAMIC VIEW MONITOR SYSTEM	○	-	-	-	○	-	-
SAFETY CONNECT SYSTEM	○	-	-	-	○	-	-
TOYOTA ENTUNE SYSTEM	○	-	-	-	-	-	-
2GR-FKS CHARGING SYSTEM	○	-	○	-	○	○	-
LIN COMMUNICATION SYSTEM	○	-	-	-	○	-	-
CAN COMMUNICATION SYSTEM	○	-	-	-	-	-	-
POWER DOOR LOCK CONTROL SYSTEM	-	-	-	-	○	○	○
WIRELESS DOOR LOCK CONTROL SYSTEM (w/ Smart Key System)	○	-	-	-	○	○	○
WIRELESS DOOR LOCK CONTROL SYSTEM (w/o Smart Key System)	○	-	-	-	○	○	○
KEY REMINDER WARNING SYSTEM	-	-	-	-	○	-	-
SMART KEY SYSTEM (for Entry Function)	○	-	-	-	○	○	○
SMART KEY SYSTEM (for Start Function)	○	-	-	-	○	○	○
ENGINE IMMOBILISER SYSTEM (w/ Smart Key System)	○	-	-	-	○	○	-
ENGINE IMMOBILISER SYSTEM (w/o Smart Key System)	○	-	-	-	○	○	-
THEFT DETERRENT SYSTEM	-	-	-	-	○	○	○
LIGHTING SYSTEM (INT)	-	-	-	-	○	○	○
METER / GAUGE SYSTEM	○	-	-	-	○	○	○
AIRBAG SYSTEM	○	○	-	-	○	-	-
OCCUPANT CLASSIFICATION SYSTEM	○	-	-	-	○	-	-
PRE-COLLISION SYSTEM	○	-	○	-	○	○	○
FRONT POWER SEAT CONTROL SYSTEM (w/ Memory)	○	-	-	-	○	○	○
AUTO ACCESS SEAT SYSTEM	○	-	-	-	-	-	-
SEAT BELT WARNING SYSTEM	-	-	-	-	○	○	○
AIR CONDITIONING SYSTEM	○	-	-	-	○	○	○
POWER WINDOW CONTROL SYSTEM	○	-	-	-	○	○	○
WINDOW DEFOGGER SYSTEM	-	-	-	-	-	○	-
POWER SLIDE DOOR SYSTEM	○	-	-	-	○	○	○
SLIDE DOOR CLOSER SYSTEM	○	-	-	-	○	-	-
BACK DOOR CLOSER SYSTEM	○	-	-	-	○	○	-
POWER BACK DOOR SYSTEM	○	-	-	-	○	○	○
POWER MIRROR CONTROL SYSTEM (w/ Memory)	○	-	-	-	○	○	-
POWER MIRROR CONTROL SYSTEM (w/o Memory)	-	-	-	-	-	○	-
LIGHTING SYSTEM (EXT)	○	-	-	-	○	○	○

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 for DTCs, depending on the case, may result in unnecessary troubleshooting for systems operating normally or lead to repairs not related to the problem. Follow the procedure listed in the flowchart in the correct order.

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.

Result

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).

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.

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 following symptom simulation tests are effective substitutes for the conditions and can be applied to 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 Problem Symptoms Table for each system to narrow down the possible causes.

To reproduce DTCs, it is necessary to satisfy the respective DTC detection conditions.

(a) VIBRATION METHOD: When a malfunction seems to occur as a result of vibration.

Apply slight vibration with a finger to the part of the sensor suspected to be the cause of the problem, and check whether the malfunction occurs.

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.

If the vehicle has or had a water leak problem, the leak may have damaged the ECU or connections. Look for evidence of corrosion or short circuits. Proceed with caution during water tests.

(d) HIGH ELECTRICAL LOAD METHOD: When a malfunction seems to occur when the electrical load is high.

(1) Turn on the heater blower, headlights, rear window defogger and all other electrical loads. Check if the malfunction recurs.

Look for output Diagnostic Trouble Codes (DTCs) (from the DTC checks) in the appropriate section's Diagnostic Trouble Code Chart. Use the chart to determine the trouble area and the proper inspection procedure. A description of each of the chart's columns is shown in the table below.

When no DTC is output but the problem still occurs, use the Problem Symptoms Table. The suspected areas (circuits or parts) for each problem symptom are shown in the table. The suspected areas are listed in order of probability. A description of each of the table columns is shown in the following table.

In some cases, the problem is not detected by the diagnostic system even though a problem symptom occurs. It is possible that the problem occurs outside the detection range of the diagnostic system, or that the problem occurs in a completely different system.

A description of the main points for inspection of suspected areas is shown in the following table.