Engine Controls - Diagnostics: Pre-Check

Description

• When troubleshooting On-Board Diagnostic (OBD II) vehicles, the vehicle must be connected to the OBD II scan tool (in compliance with SAE J1978) or the hand-held tester. Various data output from the vehicle's ECM can then be read.
• OBD II regulations require that the vehicle's on-board computer illuminates the Malfunction Indicator Lamp (MIL) on the instrument panel when the computer detects a malfunction in: 1) the emission control system/components, or 2) the powertrain control components (which affect vehicle emissions), or 3) the computer. In addition, the applicable Diagnostic Trouble Codes (DTCs) prescribed by SAE J2012 are recorded in the ECM memory (see DIAGNOSTIC TROUBLE CODE CHART ).
  Fig 1: Identifying Malfunction Indicator Lamp

  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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

• To check the DTC, connect the hand-held tester or OBD II scan tool to the Data Link Connector 3 (DLC3) on the vehicle. The hand-held tester or OBD II scan tool also enables you to erase the DTC and check the freeze frame data and various forms of engine data (for operating instructions, see the OBD II scan tool's instruction book). The DTC includes SAE controlled codes and manufacturer controlled codes. SAE controlled codes must be set as prescribed by the SAE, while manufacturer controlled codes can be set freely by a manufacturer within the prescribed limits (see DIAGNOSTIC TROUBLE CODE CHART ).
• 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. A "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 (hand-held tester only) (see step  5).
  Fig 2: Connecting Hand Held Tester To DLC3 Connector

  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
• *2 trip detection logic:

  When a malfunction is first detected, the malfunction is temporarily stored in the ECM memory (1st trip). If the ignition switch is turned OFF and then ON again, and the same malfunction is detected again, the MIL will illuminate (2nd trip).

• Freeze frame data:

  The freeze frame data records the engine conditions (fuel system, calculated load, engine coolant temperature, fuel trim, engine speed, vehicle speed, etc.) when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.

Priorities for troubleshooting:

When multiple DTCs occur, find out the order in which the DTCs should be inspected by checking the component's DTC chart. If no instructions are written in the DTC chart, check DTCs in the following order of priority:

1. DTCs other than fuel trim malfunction (DTC P0171, P0172) and misfire (DTC P0300 - P0304).
2. Fuel trim malfunction (DTC P0171, P0172).
3. Misfire (DTC P0300 - P0304).

The vehicle's ECM uses the ISO 9141-2 for communication protocol. The terminal arrangement of the DLC3 complies with SAE J1962 and matches the ISO 9141-2 format.

Fig 3: Identifying DLC3 Connector Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

HINT:

Connect the cable of the hand-held tester or the OBD II scan tool to the DLC3, turn the ignition switch ON and attempt to use the hand-held tester or the OBD II scan tool. If the screen displays UNABLE TO CONNECT TO VEHICLE, 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 communication is still impossible when the tool is connected to another vehicle, the problem is probably in the tool itself, so consult the Service Department listed in the tool's instruction manual.

Battery voltage: 11 to 14 V 

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

1. The MIL turns on when the ignition switch is turned ON and the engine is not running.

   HINT:

   If the MIL is not illuminated, troubleshoot the MIL circuit (see MIL CIRCUIT MALFUNCTION ).

2. When the engine is started, the MIL should turn off. If the lamp remains on, it means that the diagnosis system has detected a malfunction or abnormality in the system.

1. Checking DTCs using the hand-held tester or OBD II scan tool.
   1. Connect the hand-held tester or the OBD II scan tool to DLC3.
   2. Turn the ignition switch ON.
   3. Use the hand-held tester or the OBD II scan tool to check the DTCs and freeze frame data and then write them down.

      For the hand-held tester, enter the following menus: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES. For the OBD II scan tool, see its instruction manual.

   4. See DIAGNOSTIC TROUBLE CODE CHART  to confirm the details of the DTCs.
      Fig 4: Connecting Hand-Held Tester To DLC3 Connector

      Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   NOTE: When simulating a symptom with the OBD II scan tool (excluding hand-held tester) to check for DTCs, use the normal mode. For DTCs subject to "2 trip detection logic", perform either of the following actions.

   • Turn the ignition switch OFF after the symptom is simulated once. Then repeat the simulation process again. When the problem has been simulated twice, the MIL lights up and the DTCs are recorded in the ECM.
   • Check the pending fault code using the Continuous Test Results function (Mode 7 for SAE J1979) on the OBD II scan tool.
2. Clearing the DTCs using the hand-held tester or the OBD II scan tool.
   1. Connect the hand-held tester or the OBD II scan tool to the DLC3.
   2. Turn the ignition switch ON.
   3. Erase DTCs and freeze frame data using the hand-held tester or the OBD II scan tool (complying with SAE J1978).

      For the hand-held tester: 1) enter the following menus: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CLEAR CODES; and 2) press YES. For the OBD II scan tool, see its instruction manual.

3. Clearing the DTCs without using the hand-held tester or the OBD II scan tool.
   1. Remove the EFI1 fuse from the engine room J/B and ETCS fuse from the engine room R/B for more than 60 seconds. Or, disconnect the battery terminal for more than 60 seconds.

      After disconnecting the battery terminal, perform the "INITIALIZE" procedure (see PRE-CHECK in Automatic Transaxle Diagnostics article).

      Fig 5: Locating Engine Room J/B EFI1 Fuse And Engine Room R/B ETCS Fuse

      Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

HINT:

Hand-held tester only:

Check mode has a higher sensitivity to detect malfunctions and can detect malfunctions that normal mode cannot detect.

Check mode can also detect all the malfunctions that normal mode can detect.

1. Procedure for Check Mode using the hand-held tester.
   1. Make sure that the items below are true:
      • Battery positive voltage 11 V or more.
      • Throttle valve fully closed.
      • Transmission in the P or N position.
      • A/C switched OFF.
   2. Turn the ignition switch OFF.
   3. Connect the hand-held tester to the DLC3.
   4. Turn the ignition switch ON.
      Fig 6: Connecting Hand Held Tester To DLC3 Connector

      Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   5. Change the ECM to check mode with the hand-held tester. Enter the following menus: DIAGNOSIS / ENHANCED OBD II / CHECK MODE. Make sure the MIL flashes as shown in the illustration.
      NOTE: All DTCs and freeze frame data recorded will be erased if: 1) the hand-held tester is used to change the ECM from normal mode to check mode or vice-versa; or 2) during check mode, the ignition switch is turned from ON to ACC or OFF.