Toyota RAV4 manuals

Toyota Sienna Service Manual: 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.

Symptom simulation

(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 (140°F).

    Exceeding this temperature may damage the components.

  • Do not apply heat directly to the parts in the ECU.

Symptom simulation

(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.

Symptom simulation

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

(1) Turn on the heater blower, headlight, rear window defogger and all other electrical loads.

Check if the malfunction reoccurs.

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 malfunctio ...

Diagnostic trouble code chart
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 inspecti ...

Other materials:

Terminals of ECU
1. COMBINATION METER ASSEMBLY *1: with Power Rear No. 2 Seat with Stowing Function *2: with Theft Deterrent System  Waveform 1 (Reference) : Using an oscilloscope: OK: HINT: As vehicle speed increases, the cycle of the signal waveform narrows. Wavefor ...

Check mode procedure
HINT: Intelligent tester only: Compared to normal mode, check mode is more sensitive to malfunctions. Therefore, check mode can detect the malfunctions that cannot be detected by normal mode. NOTICE:All the stored DTCs and freeze frame data are erased if: 1) the ECM is changed fro ...

On-vehicle inspection
1. INSPECT CURTAIN SHIELD AIRBAG ASSEMBLY (VEHICLE NOT INVOLVED IN COLLISION)  Perform a diagnostic system check. With the curtain shield airbag assembly installed on the vehicle, perform a visual check. If there are any defects as mentioned below, replace the front pillar garn ...

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