Diagnosis System

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CHECK DLC3

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.

Fig 1: Identifying DLC3 Connector Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

CONNECTOR TERMINALS REFERENCE TABLE

Symbols (Terminal No.)

Terminal Description

Condition

Pulse condition

SIL (7) - SG (5)

Bus "+" Line

During transmission

Pulse generation

CG (4) - Body ground

Chassis Ground

Always

Below 1 Ω

SG (5) - Body ground

Signal ground

Always

Below 1 Ω

BAT (16) - Body ground

Battery positive

Always

10 to 14 V

CANH (6)-CANL (14)

CAN bus line

Power switch off (⁽¹⁾)

54 to 69 Ω

CANH (6)-BAT (16)

HIGH-level CAN bus line

Power switch off (⁽¹⁾)

6 kΩ or higher

CANH (6) - CG (4)

HIGH-level CAN bus line

Power switch off (⁽¹⁾)

200 Ω or higher

CANL (14)-BAT (16)

LOW-level CAN bus line

Power switch off (⁽¹⁾)

6 kΩ or higher

CANL (14)-CG (4)

LOW-level CAN bus line

Power switch off (⁽¹⁾)

200 Ω or higher

NOTE:

⁽¹⁾	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 door.

If the result is not as specified, the DLC3 may have a malfunction. Repair or replace the harness and connector.

HINT:

If the display shows a communication error message when connecting the cable of the intelligent tester to the DLC3, turning the power switch on (IG) and operating the intelligent tester, there is a problem on the vehicle side or tester side.

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 tester is connected to another vehicle, the problem is probably in the tester itself. Consult the Service Department listed in the tester's instruction manual.

SYMPTOM SIMULATION
HINT:

The most difficult case in troubleshooting is when no symptoms occur. 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 customer's vehicle should be simulated. No matter how experienced or skilled a technician may be, if he proceeds to troubleshoot without confirming the problem symptoms, he will likely overlook something important and make a wrong guess at some points in the repair operation. This leads to a standstill in troubleshooting.
1. 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 is turned 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.
    
    Fig 2: Identifying Connectors & Sensors Vibration
    Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    
    The connector joint and fulcrum of the vibration are the major areas to be checked thoroughly.
2. Simulation method for DTC B1794:
  Turn the power switch from the off to on (IG), hold it for 10 seconds, and back to off again 50 times in a row.
  
  HINT:
  
  DTC B1794 is output if the occupant classification ECU receives the power switch off-on (IG)-off signal 50 times in a row when a malfunction occurs in the power circuit for the occupant classification system.

FUNCTION OF PASSENGER AIRBAG ON/OFF INDICATOR

Initial check.

Turn the power switch on (IG).
The passenger airbag ON/OFF indicator ("ON" and "OFF") comes on for approximately 4 seconds, then goes off for approximately 2 seconds.

Approximately 6 seconds after the power switch is turned to on (IG), the passenger airbag ON/ OFF indicator will show ON or OFF depending on the conditions listed below.

CONDITION TABLE

Condition

ON Indicator

OFF Indicator

Vacant

OFF

Adult is seated. (Above 36 kg (79.37 lb))

OFF

Child is seated. (Less than 36 kg (79.37 lb))

OFF

Child restraint system is set. (⁽¹⁾)

OFF

Front passenger occupant classification system failure

OFF

⁽¹⁾	Child restraint system less than 7 kg (15.43 lb) and passenger side buckle switch is ON, then 7 to 36 kg (15.43 to 79.37 lb) is set.

HINT:

The passenger airbag ON/OFF indicator is based on Fig 3 below in order to check the indicator light circuit.
When the occupant classification system has trouble, both the SRS warning light and the passenger airbag ON/OFF indicator ("OFF") come on. In this case, check the DTCs in "AIRBAG SYSTEM" first.

Fig 3: Identifying Timing Diagram Of Passenger Airbag ON/OFF Indicator
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

CHECK PASSENGER AIRBAG ON/OFF INDICATOR
1. Turn the power switch on (IG).
2. Check that the passenger airbag ON/OFF indicator ("ON" and "OFF") come on for approximately 4 seconds, then goes off for approximately 2 seconds.
  HINT:
  
  Refer to the table in step 3 regarding the passenger airbag ON/OFF indicator when the power switch is turned on (IG) and approximately 6 seconds pass.
  
  Fig 4: Identifying Passenger Airbag ON/OFF Indicator
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002