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Toyota Corolla Repair Manual: Symptom simulation


: the most difficult case in troubleshooting is when no symptoms occurs. In such cases, a thorough customer problem analysis must be carried out. Then the same or similar conditions and environment in which the problem occurred in the customers vehicle should be simulated. No matter how much experience a technician has, or how skilled he may be, if he proceeds to troubleshoot without confirming the problem symptoms, he will tend to overlook something important in the repair operation and make a wrong guess somewhere, which will only lead to a standstill. For example, for a problem which only occurs when the engine is cold, or for a problem which occurs due to vibration caused by the road during driving, etc., The problem can never be determined when the engine is hot or when the vehicles is at a standstill. Since vibration, heat or water penetration (moisture) is a likely cause for the problem which is difficult to reproduce, the symptom simulation tests introduced here are effective measures in a point that the external causes are applied to the vehicle in a stationary condition.

Important points in the symptom simulation test: in the symptom simulation test, the problem symptoms should be confirmed, and the problem area or parts must also be discovered. To do so, reduce the possible problem circuits according to the symptoms before starting this type of test and have the handheld tester connected beforehand. After that, carry out the symptom simulation test, judging whether the circuit being tested is defective or normal and also confirming the problem symptoms at the same time. Refer to the problem symptoms table of each system to narrow down the possible causes of the symptom.

1. Vibration method: when vibration seems to be the major cause.

  1. Part and sensor
  1.  apply slight vibration with your finger to the part of the sensor considered to be the problem cause and check whether the malfunction occurs.


: applying strong vibration to relays may result in open relays.

  1. Connectors
  1.  slightly shake the connector vertically and horizontally.
  1.  wire harness
  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

2. Heat method: if the problem 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 object. Check if the malfunction occurs.



3. Water sprinkling method: when the malfunction seems to occur on a rainy

3. Water sprinkling method: when the malfunction seems to occur on a rainy day or in highhumidity.

  1. Sprinkle water onto the vehicle and check if the malfunction occurs.




: if a vehicle is subject to water leakage, the leaking water may contaminate the ecu. When testing a vehicle with a water leakage problem, this factor must also be considered.

4. Others: if the malfunction seems to occur when electrical load is

4. Others: if the malfunction seems to occur when electrical load is excessive.

  1. Turn on all the electrical equipment including the heater blower, headlights, rear window defogger, etc., And check if the malfunction occurs.

Diagnostic trouble code chart

Symptom confirmation and diagnostic trouble code
Hint: the diagnostic system in corolla has various functions. The first function is the diagnostic trouble code (dtc) check, in which a malfunction in the signal circuits to the ecu is sto ...

Diagnostic trouble code chart
The inspection procedures are shown in the table below. This table allows efficient and accurate troubleshooting using the diagnostic trouble codes displayed in the diagnostic trouble code chart. ...

Other materials:

Circuit description
The airbag sensor front lh circuit consists of the airbag sensor assy center and airbag sensor front lh. Dtc b1158/b1159/16 is recorded when malfunction is detected in the airbag sensor front lh circuit. Wiring diagram ...

Inspection procedure
1 Inspect park/neutral position switch assy Disconnect the park/neutral position switch connector.  measure resistance according to the value(s) in the table below when the shift lever is moved to each position. Standard: 2 Check harness and connector(park/neutral position ...

Installing the spare tire
1 Remove any dirt or foreign matter from the wheel contact surface. If foreign matter is on the wheel contact surface, the wheel nuts may loosen while the vehicle is in motion, causing the tire to come off. 2 Install the tire and loosely tighten each wheel nut by hand by approximately the sa ...

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