Diagnosis System

SUPPLEMENTAL RESTRAINT SYSTEM: AIRBAG SYSTEM: DIAGNOSIS SYSTEM

DIAGNOSIS SYSTEM

1. DESCRIPTION
The center airbag sensor controls the functions of the Supplemental Restraint System (SRS) on the vehicle. Data of the SRS can be read in the Data Link Connector 3 (DLC3) of the vehicle. When the system seems to be malfunctioning, use the Techstream to check for a malfunction and perform repairs.
2. CHECK DLC3





(a) The ECU uses ISO 15765-4 for communication. The terminal arrangement of the DLC3 complies with SAE J1962 and matches the ISO 15765-4 format.





NOTE: *: Before measuring the resistance, leave the vehicle as is for at least 1 minute and do not operate the power switch, any other switches or the doors.
If the result is not as specified, the DLC3 may have a malfunction. Repair or replace the harness and connector.
HINT: Connect the cable of the Techstream to the DLC3, turn the power switch ON (IG) and attempt to use the tester. If the display indicates that a communication error has occurred, there is a problem either with the vehicle or with the Techstream.
- If communication is normal when the tester is connected to another vehicle, inspect the DLC3 on the original vehicle.
- If communication is still not possible when the tool is connected to another vehicle, the problem is probably in the tester itself. Consult the Service Department listed in the tester's instruction manual.

3. 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 power switch ON (IG)).
(1) Slightly vibrate the part of the sensor considered to be the problem cause with your fingers and check whether the malfunction occurs.
HINT: 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.
The connector joint and fulcrum of the vibration are the major areas to be checked thoroughly.

4. FUNCTION OF SRS WARNING LIGHT
(a) Primary check.
(1) Turn the power switch OFF. Wait for at least 2 seconds, then turn the power switch ON (IG). The SRS warning light comes on for approximately 6 seconds and the 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 (for 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:
- The SRS warning light comes on.
- The SRS warning light goes off, and then comes on. This blinking pattern indicates a source voltage drop. The SRS warning light goes off 10 seconds after the source voltage returns to normal.

(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 power switch is turned ON (IG)).
(2) When the airbag system has trouble:

- The SRS warning light remains on even after the primary check period has elapsed.
- The SRS warning light goes off after the primary check, but comes on again during the constant check.
- The SRS warning light does not come on when turning the power switch from OFF to ON (IG).
HINT: The center airbag sensor keeps the SRS warning light on if the airbag has been deployed.

5. SRS WARNING LIGHT CHECK





(a) Turn the power switch ON (IG), 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 power switch is turned ON (IG) (constant check).
HINT: When any of the following symptoms occur, refer to the "Problem Symptoms Table" Problem Symptoms Table.
- The SRS warning light comes on occasionally after the primary check period has elapsed.
- The SRS warning light comes on, but a DTC is not output.
- The power switch is turned from OFF to ON (IG), but the SRS warning light does not come on.

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 shutting off external electricity to prevent accidental airbag activation.
(b) RELEASE METHOD 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 illustrations below 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.
NOTICE:
- Do not release the activation prevention mechanism unless specially directed by the troubleshooting procedure.
- To prevent the terminal and the short spring from being damaged, always use a piece of paper of the same thickness as the male terminal.