Diagnosis System

DESCRIPTION

DIAGNOSTIC SYSTEM
When troubleshooting a vehicle with a diagnostic system, the only difference from the usual troubleshooting procedure is connecting the hand-held tester to the vehicle and reading various data output from the vehicle's steering lock ECU.

The steering lock ECU records DTCs when the computer detects a malfunction in the computer itself or in its circuits.

To check the DTCs, connect the hand-held tester to the DLC3 on the vehicle. The hand-held tester enables you to erase the DTCs, activate the several actuators and check data list.

Check the DLC3.

The steering lock ECU follows the CAN and ISO 9141-2 communication protocol. The terminal arrangement of the DLC3 complies with SAE J1962 and matches the ISO 9141-2 format.

Fig 1: Identifying DLC3 Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

DLC3 TERMINALS SPECIFIED CONDITIONS

Symbols (Terminals 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 Ω
SG (5) - Body ground	Signal ground	Always	Below 1 Ω
BAT (16) - Body ground	Battery positive	Always	11 to 14V
CANH (6) - CANL (14)	HIGH-level CAN bus line	IG switch OFF	54 to 67 Ω
CANH (6) - Battery positive	HIGH-level CAN bus line	IG switch OFF	1 MΩ or higher
CANH (6) - CG (4)	HIGH-level CAN bus line	IG switch OFF	3 kΩ or higher
CANL (14) - Battery positive	LOW-level CAN bus line	IG switch OFF	1 MΩ or higher
CANL (14)-CG (4)	LOW-level CAN bus line	IG switch OFF	3 kΩ or higher

HINT:

If the display shows "UNABLE TO CONNECT TO VEHICLE" after connecting the hand-held tester cable to the DLC3 and turning the ignition switch to the ON position, there is a problem with either the vehicle or tester.

If communication is normal when connecting the tester to another vehicle, inspect the DLC3 on the original vehicle.
If communication is still not possible when connecting the tester to another vehicle, the problem is probably on the tester itself, so consult the Service Department listed in the tester's operator's manual.