Engine - Diagnostics: Pre-Check

1. Description

   When troubleshooting OBD II (On-Board Diagnostics) vehicles, a hand-held tester or OBD II scan tool (complying with SAE J1987) must be connected to the DLC3 (Data Link Connector 3) of the vehicle. Various data in the vehicle's ECM (Engine Control Module) can be then read. OBD II regulations require that the vehicle's on-board computer illuminates the MIL (Malfunction Indicator Lamp) on the instrument panel when the computer detects a malfunction in:

   • The emission control systems and components
   • The power train control components (which affect vehicle emissions)
   • The computer itself

   In addition, the applicable DTCs (Diagnostic Trouble Codes) prescribed by SAE J2012 are recorded in 3 consecutive trips, the MIL turns off automatically but the DTCs remain recorded in the ECM (Engine Control Module) memory.

   Fig 1: Identifying MIL (Malfunction Indicator Lamp)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   To check the DTCs, connect a hand-held tester or OBD II scan tool to the DLC3. The tester and scan tool display DTCs, freeze frame data, and a variety of engine data. The DTCs and freeze frame data can be erased with the tester and scan tool (see HOW TO PROCEED WITH TROUBLESHOOTING ).

   Fig 2: Connecting Hand-Held Tester To DLC3

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Normal mode and check mode

   The diagnosis system operates in the 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 as an option for technicians. In check mode, 1 trip detection logic is used for simulating malfunction symptoms and increasing the system's ability to detect malfunctions, including intermittent problems (hand-held tester only).

3. 2 trip detection logic

   When a malfunction is first detected, the malfunction is temporarily stored in the ECM memory (1st trip). If the same malfunction is detected during the next sequent drive cycle, the MIL is illuminated (2nd trip).

4. Freeze frame data

   The freeze frame data record the engine conditions (fuel system, calculated engine load, engine coolant temperature, fuel trim, engine speed, vehicle speed, etc.) when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, 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.

5. DLC3 (Data Link Connector 3)

   The vehicle's ECM uses the ISO 9141-2 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
   DATA LINK CONNECTOR TERMINALS REFERENCE
   
   

   Symbols	Terminal No.	Names	Reference Terminals	Results	Conditions
   SIL	7	Bus "+" line	5 - Signal ground	Pulse generation	During transmission
   CG	4	Chassis ground	Body ground	Below 1 Ω	Always
   SG	5	Signal ground	Body ground	Below 1 Ω	Always
   BAT	16	Battery positive	Body ground	9 to 14 V	Always

   HINT:

   The DLC3 is the interface prepared for reading various data from the vehicle's ECM. After connecting the cable of a hand held tester or OBD II scan tool, turn the ignition switch to ON and turn the tester or scan tool ON.

   If a communication failure message is displayed on the tester or scan tool screen (on the tester: UNABLE TO CONNECT TO VEHICLE), a problem exists in either the vehicle or tester. In order to identify the location of the problem, connect the tester to another vehicle.

   • If communication is normal: Inspect the DLC3 on the original vehicle.
   • If communication is impossible: The problem is probably with the tester itself. Consult the Service Department listed in the instruction manual.
6. Battery voltage
   1. Battery voltage: 11 to 14 V 

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

7. MIL (Malfunction Indicator Lamp)
   1. The MIL illuminates when the ignition switch is turned to ON and the engine is not running.

      HINT:

      If the MIL does not illuminate, check the MIL circuit (see MIL Circuit Malfunction ).

   2. The MIL should turn off when the engine is started.

      If the MIL remains on, the diagnosis system has detected a malfunction or abnormality in the system.

When the diagnosis system is changed from normal mode to check mode or vice versa, all DTCs and freeze frame data recorded in normal mode are erased. Before changing modes, always check and make a note of DTCs and freeze frame data. 

HINT:

• DTCs which are stored in the ECM can be displayed on a hand-held tester or OBD II scan tool. A hand-held tester can display current and pending DTCs.
• Some DTCs are not set if the ECM does not detect the same malfunction again during a second consecutive driving cycle. However, such malfunctions, detected on only one occasion, are stored as pending DTCs.
• The pending DTCs are set when the malfunction is detected once.

1. Check DTCs (using a hand-held tester or OBD II scan tool)
   1. Connect a hand-held tester or OBD II scan tool to the DLC3.
   Fig 4: Connecting Hand-Held Tester To DLC3
   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   2. Turn the ignition switch to ON.
   3. Turn the tester or scan tool ON.
   4. For the tester, select the following menu items:

      DIAGNOSIS/ENHANCED OBD II/DTC INFO/CURRENT CODES or PENDING CODES.

   5. For the scan tool, refer to the instruction manual.
   6. Check DTCs and freeze frame data, and then write them down.
   7. See DIAGNOSTIC TROUBLE CODE CHART  to check the details of DTCs.

   HINT:

   When simulating a symptom with an OBD II scan tool to check DTCs in the DIAGNOSTIC TROUBLE CODE CHART, subject to 2 trip detection logic, conduct either of the following operations. (For more information, refer to the scan tool instruction manual.)

   • Check pending DTCs using the Continuous Test Result function (Mode 07 for SAE J1979).
   • Simulate the symptom again after turning the ignition switch to OFF upon finishing the first symptom simulation, so that the MIL is illuminated and the DTC(s) is stored in the ECM.
2. Clear DTCs (using a hand-held tester or OBD II scan tool)
   1. Connect a hand-held tester or OBD II scan tool to the DLC3.
   2. Turn the ignition switch to ON.
   3. Turn the tester or scan tool on.
   4. For the tester, select the following menu items:

      DIAGNOSIS/ENHANCED OBD II/DTC INFO/CLEAR CODES.

   5. Press the YES button.
   6. For the scan tool, refer to the instruction manual.
3. Clear DTCs (without using a hand-held tester or OBD II scan tool)
   1. Perform either one of the following operations.
      • Disconnect the negative battery cable for more than 1 minute.
      • Remove the EFI and ETCS fuses from the engine room Junction Block (J/B) located inside the engine compartment for more than 1 minute.

When the diagnosis system is changed from normal mode to check mode or vice versa, all DTCs and freeze frame data recorded in normal mode are erased. Before changing modes, always check and make a note of DTCs and freeze frame data. 

HINT:

Hand-held tester only:

Compared to normal mode, check mode is more sensitive to malfunctions. Therefore, check mode can detect the malfunctions that cannot be detected by normal mode.

1. Procedure for check mode (using a hand-held tester)
   1. Make sure that the vehicle is in the following condition:
      • Battery voltage 11 V or more.
      • Throttle valve fully closed.
      • Shift lever is in the neutral position.
      • A/C switched OFF.
   2. Turn the ignition switch to OFF.
   3. Connect a hand-held tester to the DLC3.
   Fig 5: Identifying DLC3 Connector Location
   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   4. Turn the ignition switch to ON.
   5. Turn the tester ON.
   6. Select the following menu items: DIAGNOSIS/ENHANCED OBD II/CHECK MODE.
   7. Switch the ECM from normal mode to check mode.

      (Make sure the MIL flashes as shown in the illustration.)

      Fig 6: Identifying Pattern (MIL Flashes)

      Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   8. Start the engine. (Make sure the MIL turns off.)
   9. Simulate the conditions of the malfunction described by the customer.
   10. Check DTCs and freeze frame data using the tester.

HINT:

Do not turn the ignition switch to OFF, as turning it to OFF switches the diagnosis system from check mode to normal mode, which erases all the stored DTCs and freeze frame date.

If any of the following codes are recorded, the ECM enters fail-safe mode.

HINT:

Hand-held tester only:

Inspect the vehicle's ECM using check mode. Intermittent problems are easier to detect with the hand-held tester when the ECM is in check mode. In check mode, the ECM uses 1 trip detection logic, which is more sensitive to malfunctions than normal mode (default) that uses 2 trip detection logic.

1. Clear DTCs (see step  2).
2. Switch the ECM from normal mode to check mode using a hand-held tester.
3. Perform a simulation test (see HOW TO PROCEED WITH TROUBLESHOOTING ).
4. Check and wiggle the harness(es), the connector(s) and terminal(s) (see HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE ).

When a malfunction is not confirmed by the DTC check, troubleshooting should be carried out in all circuits considered to be possible causes of the problem. In many cases, by carrying out the basic engine check shown in the following flowchart, the location of the problem can be found quickly and efficiently. Therefore, using this check is essential when engine troubleshooting.

1. Is battery voltage 11 V or more when engine is stopped? 

   NO: Charge or replace battery. 

   YES: Go to next step. 

2. Is engine cranked? 

   NO: Proceed to  TEST  and  INSPECTION  , and continue to troubleshoot. 

   YES: Go to next step. 

3. Does engine start? 

   NO: Go to step   7 . 

   YES: Go to next step. 

4. Check air cleaner filter 

   PREPARATION: 

   Remove the air cleaner filter.

   OK: 

   Visual check that the air filter is not excessively dirty or oily.

   NG: Replace air cleaner filter. 

   OK: Go to next step. 

5. Check idling speed 

   PREPARATION: 

   1. Warm up the engine to the normal operating temperature.
   2. Switch off all the accessories.
   3. Switch off A/C.
   4. Shift the shift lever into the neutral position.
   5. Connect the hand-held tester or OBD II scan tool to the DLC3 of the vehicle.

   CHECK: 

   Check the idling speed.

   OK: 

   Idling speed: 650 to 750 RPM 

   NG: Proceed to problem symptoms table on  PROBLEM SYMPTOMS TABLE  . 

   OK: Go to next step. 

6. Check ignition timing. 

   PREPARATION: 

   1. Warm up the engine to the normal operating temperature.
   2. Shift the shift lever into the neutral position.
   3. Keep the engine speed at idle.
   4. Using SST, connect terminals TC and CG of the DLC3.

      SST 09843-18020

   5. Using a timing light, connect the tester to the No. 1 high-tension cord.

   CHECK: 

   Check the ignition timing.

   Fig 7: Checking Ignition Timing

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   OK: 

   Ignition timing: 6 to 1° BTDC at idle 

   NG: Proceed to  IGNITION SYSTEM  , and continue to troubleshoot. 

   OK: Proceed to problem symptoms table on  PROBLEM SYMPTOMS TABLE  . 

7. Check fuel pressure. 

   PREPARATION: 

   1. Be sure that the enough fuel is in the tank.
   2. Remove the cover from the pulsation damper.
   Fig 8: Removing Cover From Pulsation Damper
   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   3. Connect the hand-held tester to the DLC3.
   4. Turn the ignition switch ON and push the hand-held tester main switch ON.
   5. Use the ACTIVE TEST mode to operate the fuel pump.

      HINT:

      Please refer to the hand-held tester operator's manual for further details.

   6. If you have no hand-held tester, connect the positive (+) and negative (-) leads from the battery to the fuel pump connector (see FUEL PUMP ).

   CHECK: 

   Check that the pulsation damper screw rises up when the fuel pump operates.

   HINT:

   At this time, you will hear a fuel flowing noise.

   NG: Proceed to  FUEL PUMP  , and continue to troubleshoot. 

   OK: Go to next step. 

8. Check for spark. 

   PREPARATION: 

   1. Remove the ignition coil from the spark plug.
   2. Remove the spark plug.
   3. Install the spark plug to the ignition coil.
   4. Disconnect the injector connector.
   5. Ground the spark plug.

   CHECK: 

   Check if spark occurs while the engine is being cranked.

   Fig 9: Checking For Spark

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002