Toyota Highlander manuals

Toyota Highlander Service Manual: Symptom simulation

HINT: The most difficult case in troubleshooting is when no problem symptoms occur. In such cases, a thorough customer 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 occurs 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.

1. VIBRATION METHOD: When vibration seems to be the major cause.



  1.  Apply slight vibration with a finger to the part of the sensor considered to be the cause of the problem and check whether or not the malfunction occurs.

HINT: Applying strong vibration to relays may open relays.


  1.  Slightly shake the connector vertically and horizontally.


  1.  Slightly shake the wire harness vertically and horizontally.

    The connector joint and fulcrum of the vibration are the major areas that should be checked thoroughly.

2. HEAT METHOD: If the problem seems to occur when the area in question is heated.


(a) Heat the component that is the possible cause of the malfunction with a hair dryer or similar device. Check if the malfunction occurs.


3. WATER SPRINKLING METHOD: When the malfunction seems to occur on a rainy day or in highhumidity.


(a) Sprinkle water onto the vehicle and check if the malfunction occurs.


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 shorts. Proceed with caution during water tests.

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


(a) Turn on all the electrical loads including the heater blower, headlights, rear window defogger, etc., and check if the malfunction occurs.

Symptom confirmation and diagnostic trouble code
HINT: The diagnostic system in the HIGHLANDER 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 malfun ...

Diagnostic trouble code chart
Use Diagnostic Trouble Codes (DTCs) (from the DTC checks) in the table below to determine the trouble area and proper inspection procedure. The Supplemental Restraint System (SRS) diagnostic trou ...

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