Diagnosis System

DESCRIPTION

DIAGNOSTIC SYSTEM
When troubleshooting a vehicle with the diagnosis system, the only difference from the usual troubleshooting procedure is connecting the intelligent tester to the vehicle and reading various data output from the vehicle's clearance warning ECU.

The clearance warning ECU records DTCs when the ECU detects a malfunction in the ECU itself or in its circuits.

To check the DTCs, connect the intelligent tester to the DLC3 on the vehicle. The intelligent tester enables you to erase the DTCs, activate the various actuators, and check the freeze frame data and Data List.
Check the DLC3.
The clearance warning ECU uses the ISO 15765-4 for communication protocol. The terminal arrangement of the DLC3 complies with SAE J1962 and matches the ISO 15765-4 format.

Fig 1: Identifying DLC3 Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

TERMINAL DESCRIPTION AND SPECIFIED CONDITION

Symbols (Terminal No.)	Terminal Description	Condition	Specified Condition
SIL (7) - SG (5)	Bus "+" line	During communication	Pulse generation
CG (4) - Body ground	Chassis ground	Always	Below 1 ohms
SG (5) - Body ground	Signal ground	Always	Below 1 ohms
BAT (16) - Body ground	Battery positive	Always	11 to 14 V
CANH (6) - CANL (14)	HIGH-level CAN bus line	Engine switch off	54 to 67 ohms
CANH (6) - Battery positive	HIGH-level CAN bus line	Engine switch off	1 M ohms or higher
CANH (6) - CG (4)	HIGH-level CAN bus line	Engine switch off	3 k ohms or higher
CANL (14) - Battery positive	LOW-level CAN bus line	Engine switch off	1 M ohms or higher
CANL (14) - CG (4)	LOW-level CAN bus line	Engine switch off	3 k ohms or higher

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 intelligent tester to the DLC3, turn the engine 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 tester.

If communication is normal when the tester is connected to another vehicle, inspect the DLC3 of the original vehicle.
If communication is still not possible when the tester is connected to another vehicle, the problem may be in the tester itself. Consult the Service Department listed in the tester's instruction manual.