Toyota 4Runner: Diagnosis System

DIAGNOSIS SYSTEM

1. 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.

(a) Vibration method: When vibration seems to be the major cause.

HINT:

Perform the simulation method only during the primary check period (for approximately 6 seconds after the ignition switch is turned to ON).

(1) Slightly vibrate the part of the sensor considered to be the cause of the problem with your fingers and check whether the malfunction occurs.

NOTICE:

Shaking the relays too strongly may result in open relays.

(2) Slightly shake the connector vertically and horizontally.

(3) Slightly shake the wire harness vertically and horizontally.

HINT:

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

2. FUNCTION OF SRS WARNING LIGHT

(a) Primary check.

(1) Turn the ignition switch off. Wait for at least 2 seconds, and then turn the ignition switch to ON. The SRS warning light comes on for approximately 6 seconds and diagnosis of the airbag system (including the seat belt pretensioners) is performed.

HINT:

If trouble is detected during the primary check, the SRS warning light remains on even after the primary check period (of approximately 6 seconds) has elapsed.

(b) Constant check.

(1) After the primary check, the center airbag sensor constantly monitors the airbag system for trouble.

HINT:

If trouble is detected during the constant check, the center airbag sensor functions as follows:

(c) Review.

(1) When the airbag system is normal:

The SRS warning light comes on only during the primary check period (for approximately 6 seconds after the ignition switch is turned to ON).

(2) When the airbag system has trouble:

HINT:

The center airbag sensor functions to keep the SRS warning light on if the airbag has been deployed.

3. CHECK SRS WARNING LIGHT

(a) Turn the ignition switch to ON and check that the SRS warning light comes on for approximately 6 seconds (primary check).

(b) Check that the SRS warning light goes off approximately 6 seconds after the ignition switch is turned to ON (constant check).

HINT:

When any of the following symptoms occur, refer to the "Problem Symptoms Table" (See page ).

4. FUNCTION OF PASSENGER AIRBAG ON/OFF INDICATOR

(a) Initial check

(1) Turn the ignition switch to ON.

(2) The passenger airbag ON/OFF indicator comes on for approximately 4 seconds, and then goes off for approximately 2 seconds.

(3) Approximately 6 seconds after the ignition switch is turned to ON, the passenger airbag ON/OFF indicator will be on or off depending on the conditions listed below.

5. CHECK PASSENGER AIRBAG ON/OFF INDICATOR

(a) Turn the ignition switch to ON.

(b) Check that the passenger airbag ON/OFF indicator ("ON" and "OFF") comes on for approximately 4 seconds, and then goes off for approximately 2 seconds.

HINT:

In order to check the operation of the passenger airbag ON/OFF indicator when approximately 6 seconds have elapsed after turning the ignition switch to ON, refer to the table in the previous step.

6. ACTIVATION PREVENTION MECHANISM

(a) FUNCTION OF ACTIVATION PREVENTION MECHANISM

(1) An activation prevention mechanism is built into the connector (on the center airbag sensor side) of the airbag system squib circuit to prevent accidental airbag activation.

(2) This mechanism closes the circuit when the connector is disconnected by bringing the short spring into contact with the terminals and cutting off external electricity to prevent accidental airbag activation.

(b) RELEASING OF ACTIVATION PREVENTION MECHANISM

(1) To release the activation prevention mechanism, insert a piece of paper with the same thickness as the male terminal (approximately 0.5 mm [0.020 in.]) between the terminals and the short spring to break the connection.

(2) Refer to the following illustrations concerning connectors utilizing the activation prevention mechanism and its release method.

CAUTION:

Never release the activation prevention mechanism on the squib connector even when inspecting with the squib disconnected.