Diagnosis System

1. When troubleshooting On-Board Diagnostic (OBD II) vehicles, the vehicle must be connected to the OBD II scan tool (complying with SAE J1987). Various data output from the vehicle's ECM can then be read.
2. OBD II regulations require that the vehicle's onboard computer illuminate the Malfunction Indicator Lamp (MIL) on the instrument panel when the computer detects a malfunction in:
   Fig 1: Identifying Malfunction Indicator Lamp (MIL)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   1. The emission control system/components
   2. The power train control components (which affect vehicle emissions)
   3. The computer

      In addition, the applicable Diagnostic Trouble Codes (DTCs) prescribed by SAE J2012 are recorded in the ECM memory.

      If the malfunction does not reoccur in 3 consecutive trips, the MIL turns off automatically but the DTCs remain recorded in the ECM memory.

3. To check DTCs, connect the intelligent tester to the Data Link Connector 3 (DLC3) of the vehicle. The intelligent tester displays DTCs, the freeze frame data and a variety of the engine data.

   The DTCs and freeze frame data can be erased with the intelligent tester (See DIAGNOSIS SYSTEM  ).

   Fig 2: Connecting Intelligent Tester To DLC3

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. The diagnosis system operates in "normal mode" during normal vehicle use. In normal mode, "2 trip detection logic" is used to ensure accurate detection of malfunctions. "Check mode" is also available to technicians as an option. In check mode, "1 trip detection logic" is used for simulating malfunction symptoms and increasing the system's ability to detect malfunctions, including intermittent malfunctions.

1. When a malfunction is first detected, the malfunction is temporarily stored in the ECM memory (1st trip). If the engine switch is turned OFF and then ON again, and the same malfunction is detected again, the MIL will illuminate.

1. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air/fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction.
2. The intelligent tester displays freeze frame data recorded at five different points: 1) 3 times before the DTC is set, 2) once when the DTC is set, and 3) once after the DTC is set. The data can be used to simulate the vehicle's condition around the time of the malfunction. The data may be helpful in determining the cause of a malfunction. It may also be helpful in determining whether a DTC is being caused by a temporary malfunction.
   Fig 3: Identifying Freeze Frame Data

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. The vehicle's ECM 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 4: Identifying DLC3 Connector

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   HINT:

   Connect the cable of the intelligent tester to the DLC3, turn the ignition switch on (IG) and attempt to use the intelligent tester. If the screen displays a communication error message, a problem exists in the vehicle side or the tester side.

   If the communication is normal when the tool is connected to another vehicle, inspect the DLC3 on the original vehicle.

   If the communication is still impossible when the tool is connected to another vehicle, the problem is probably in the tool itself. Consult the Service Department listed in the tool's instruction manual.

   DLC3 CONNECTOR TERMINALS REFERENCE
   
   

   Symbols (Terminal No.)	Terminal Description	Condition	Specified 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	9 to 14 V
   CANH (6) - CANL (14)	HIGH-level CAN bus line	Ignition switch OFF	54 to 69 Ω
   CANH (6) - Battery positive	HIGH-level CAN bus line	Ignition switch OFF	1 MΩ or higher
   CANH (6) - CG (4)	HIGH-level CAN bus line	Ignition switch OFF	1 kΩ or higher
   CANL (14) - Battery positive	LOW-level CAN bus line	Ignition switch OFF	1 MΩ or higher
   CANL (14) - CG (4)	LOW-level CAN bus line	Ignition switch OFF	1 kΩ or higher

Battery voltage: 11 to 14 V 

1. If voltage is below 11 V, replace the battery before proceeding.

1. Check that the MIL illuminates when turning the ignition switch on (IG).

   If the MIL does not illuminate, there is a problem in the MIL CIRCUIT .

2. When the engine is started, the MIL should turn off.

1. For this vehicle, using the intelligent tester allows readiness codes corresponding to all DTCs to be read. When diagnosis (normal or malfunctioning) has been complete, readiness codes are set. Enter the following menus: ENHANCED OBD II / MONITOR STATUS on the intelligent tester.