Engine Control System (SFI) - Diagnostics: Pre-Check: Notes

1. Description
   • When troubleshooting OBD II vehicles, the only difference from the usual troubleshooting procedure is that you need to connect the vehicle to the OBD II scan tool complying with SAE J1978 or the hand-held tester, and read the various data output from the vehicle's ECM.
   • OBD II regulations require that the vehicle's on board computer illuminates the Malfunction Indicator Light (MIL) on the instrument panel when the computer detects a malfunction in the emission control system/components or in the powertrain control components which affect vehicle emissions, or a malfunction in the computer. In addition to the MIL illuminating when a malfunction is detected, the applicable Diagnostic Trouble Codes (DTCs) prescribed by SAE J2012 are recorded in the ECM memory (See DIAGNOSTIC TROUBLE CODE TABLE  ).

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

   Fig 1: Identifying Troubleshooting Diagnosis System

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   • To check the DTC, connect the hand-held tester or OBD II scan tool to the Data Link Connector 3 (DLC3) of 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 the DTC TABLE  ).
   • The diagnosis system operates in the normal mode during normal vehicle use. It also has a check mode for technicians to simulate malfunction symptoms and troubleshoot it. Most DTCs use the 2 trip detection logic* to prevent erroneous detection, and to ensure a thorough malfunction detection. By switching the ECM to the check mode when troubleshooting, a technician can cause the MIL to illuminates for a malfunction that is only detected once or momentarily (hand-held tester only) (see step  3).
   Fig 2: Connecting Hand-Held Tester Or OBD II Scan Tool To Data Link Connector

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   • *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 again during the second drive test, this second detection causes the MIL to illuminates (2nd trip) (However, the ignition switch must be turned OFF between the 1st trip and 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, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.

   Priorities for troubleshooting:

   If troubleshooting priorities for multiple DTCs are given in the applicable DTC table, these priorities should be followed. If no instructions are given, perform troubleshooting for those DTCs according to the following priorities.

   1. DTCs other than fuel trim malfunction (DTCs P0171, P0172, P0174 and P0175) and misfire (DTCs P0300 - P0306).
   2. Fuel trim malfunction (DTCs P0171, P0172, P0174 and P0175).
   3. Misfire (DTCs P0300 - P0306).
2. Check the DLC3.

   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 Terminal

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   TERMINAL CONDITION
   
   

   Symbol	Terminal No.	Connection/Voltage or Resistance	Condition
   SIL	7	Bus + Line/Pulse generation	During transmission
   CG	4	Chassis Ground - Body Ground/1 Ω or less	Always
   SG	5	Signal Ground - Body Ground/1 Ω or less	Always
   BAT	16	Battery Positive - Body Ground/9 to 14 V	Always

   HINT:

   If the display shows UNABLE TO CONNECT TO VEHICLE when you have connected the cable of the OBD II scan tool or the hand-held tester to the DLC3, turned the ignition switch ON and operated the scan tool, there is a problem on the vehicle side or tool 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, so consult the Service Department listed in the tool's instruction manual.
3. Inspect the battery voltage.

   Battery Voltage: 11 to 14 V 

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

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

      HINT:

      If the MIL does not illuminate, troubleshoot the MIL circuit (See MIL CIRCUIT  ).

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

DTC CHECK 

1. Checking DTCs using the OBD II scan tool or hand-held tester.
   1. Connect the OBD II scan tool or hand-held tester to the DLC3.
   2. Turn the ignition switch ON.
      Fig 4: Connecting OBD II Scan Tool Or Hand-Held Tester To DLC3

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   3. Use the OBD II scan tool or the hand-held tester to check the DTCs and freeze frame data and note them down (for operating instructions, see the OBD II scan tool's instruction book).

      If there is no DTC in the normal mode, check the 1st trip DTC using the Continuous Test Results function (Mode 7 for SAE J1979) on the OBD II scan tool or the hand-held tester.

   4. See DIAGNOSTIC TROUBLE CODE TABLE  to confirm the details of the DTCs.
   NOTE:

   • When simulating a symptom with the OBD II scan tool (excluding hand-held tester) to check the DTCs, use the normal mode. For code on the DTC table 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 1st trip DTC using Mode 7 (Continuous Test Results) for SAE J1979.
2. Clearing the DTCs using the OBD II scan tool or the hand-held tester.
   1. Connect the OBD II scan tool or the hand-held tester to the DLC3.
   2. Turn the ignition switch ON.
   3. When operating an OBD II scan tool (complying with SAE J1978) or the hand-held tester to erase the codes, the DTCs and freeze frame data will be erased. (See the OBD II scan tool's instruction book for operating instructions.)
3. Clearing the DTCs not using the OBD II scan tool or the hand-held tester.
   1. Disconnect the battery terminal or remove the EFI No. 1 and ETCS fuses from the engine room J/B more than 60 seconds.

DTC CHECK 

HINT:

Hand-held tester only:

Compared to the normal mode, the check mode has more sensing ability to detect malfunctions. Furthermore, the same diagnostic items which are detected in the normal mode can also be detected in the check mode.

1. Procedure for Check Mode using the hand-held tester.
   1. Check the initial conditions.
      • 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 5: Connecting Hand-Held Tester To DLC3

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   5. Switch the hand-held tester from the normal mode to the check mode (check that the MIL flashes).
      NOTE: If the hand-held tester switches the ECM from the normal mode to the check mode or vice-versa, or if the ignition switch is turned from ON to ACC or OFF during the check mode, the DTC and freeze frame data will be erased.
   6. Start the engine (MIL goes off after the engine starts).
      Fig 6: Checking MIL Flashes

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   7. Simulate the conditions of the malfunction described by the customer.
      NOTE: Leave the ignition switch ON until you have checked the DTC, etc.
   8. After simulating the malfunction conditions, use the hand-held tester diagnosis selector to check the DTC and freeze frame data, etc.

      HINT:

      Be sure not to turn the ignition switch OFF, as turning it OFF switches the diagnosis system from the check mode to the normal mode, which erases all the DTCs, etc.

   9. After checking the DTC, inspect the applicable circuit.
2. Clearing the DTCs using the OBD II scan tool or the hand-held tester.
   1. Connect the OBD 11 scan tool or the hand-held tester to the DLC3.
   2. Turn the ignition switch ON.
   3. When operating an OBD II scan tool (complying with SAE J1978) or the hand-held tester to erase the codes, the DTCs and freeze frame data will be erased. (See the OBD II scan tool's instruction book for operating instructions.)
3. Clearing the DTCs not using the OBD II scan tool or the hand-held tester.
   1. Disconnect the battery terminal or remove the EFI No. 1 and ETCS fuses from the engine room J/B more than 60 seconds.

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

Fig 7: Fail-Safe Table

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Hand-held tester only:

By putting the vehicle's ECM in the check mode, the 1 trip detection logic is possible instead of the 2 trip detection logic, and the sensitivity to detect faults is increased. This makes it easier to detect intermittent problems.

1. Clear the DTCs (See step  2).
2. Set the check mode (See step  3).
3. Perform a simulation test (See HOW TO PROCEED WITH TROUBLESHOOTING ).
4. Check the connector and terminal (See ELECTRONIC CIRCUIT INSPECTION PROCEDURE )
5. Wiggle the harness and the connector (See ELECTRONIC CIRCUIT INSPECTION PROCEDURE ).

HINT:

According to the DATA LIST displayed by the hand-held tester or the OBD II scan tool, you can read the value of the switch, sensor, actuator and so on without parts removal. Reading the DATA LIST as a first step of troubleshooting is one of the methods to shorten the diagnostic time.

1. Warm up the engine.
2. Turn the ignition switch OFF.
3. Connect the hand-held tester or the OBD II scan tool to the DLC3.
4. Turn the ignition switch ON.
5. Push the "ON" button of the hand-held tester or the OBD II scan tool.
6. Select the item "DIAGNOSIS/ENHANCED OBD II/DATA LIST".
7. According to the display on tester, read the "DATA LIST".

Fig 8: Diagnosis/Enhanced OBD II/Data List Table (1 Of 4)

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Fig 9: Diagnosis/Enhanced OBD II/Data List Table (2 Of 4)

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Fig 10: Diagnosis/Enhanced OBD II/Data List Table (3 Of 4)

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Fig 11: Diagnosis/Enhanced OBD II/Data List Table (4 Of 4)

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HINT:

Performing the ACTIVE TEST using the hand-held tester or the OBD II scan tool allows the relay, VSV, actuator and so on to operate without parts removal. Performing the ACTIVE TEST as a first step of troubleshooting is one of the methods to shorten the diagnostic time.

It is possible to display the DATA LIST during the ACTIVE TEST.

1. Warm up the engine.
2. Turn the ignition switch OFF.
3. Connect the hand-held tester or the OBD II scan tool to the DLC3.
4. Turn the ignition switch ON.
5. Push the "ON" button of the hand-held tester or the OBD II scan tool.
6. Select the item "DIAGNOSIS/ENHANCED OBD II/ACTIVE TEST".
7. According to the display on tester, perform the "ACTIVE TEST".

Fig 12: Active Test Specification Table

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