ECD SYSTEM DIAGNOSIS SYSTEM


  1. DIAGNOSIS SYSTEM


    1. Description


      • When troubleshooting Multiplex OBD (M-OBD) vehicles, the only difference from the usual troubleshooting procedure is that you connect the vehicle to the intelligent tester, and read off various data output from the vehicle's ECM.

      • The vehicle's on-board computer lights up the check engine warning light on the instrument panel when the computer detects a malfunction in the computer itself or in drive system components. In addition to the check engine warning light lighting up when a malfunction is detected, the applicable diagnostic trouble codes are recorded in the ECM memory Click here.

      If the malfunction has been repaired, the check engine warning light goes off automatically but the diagnostic trouble codes remain recorded in the ECM memory.


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        To check the diagnostic trouble codes, connect the intelligent tester to Data Link Connector 3 (DLC3) on the vehicle or read the number of blinks of the check engine warning light when TC and CG terminals on the DLC3 are connected. The intelligent tester also enables you to erase the diagnostic trouble codes and activate the several actuators and check freeze frame date and various forms of engine data. (For operating instructions, see the intelligent tester instruction book.)

      • The diagnosis system operates in normal mode during normal vehicle use. It also has a check (test) mode for technicians to simulate malfunction symptoms and troubleshoot. Some diagnostic trouble codes use 2 trip detection logic* to prevent erroneous detection and ensure thorough malfunction detection. By switching the ECM to check (test) mode using intelligent tester when troubleshooting, the technician can cause the check engine warning light to light up for a malfunction that is only detected once or momentarily (intelligent tester only) Click here.

      • *2 trip detection logic:

        When a logic malfunction is first detected, the malfunction is temporarily stored in the ECM memory.

      If the same malfunction is detected again during the second drive test, this second detection causes the check engine warning light to light up. The 2 trip repeats the same mode a 2nd time. (However, the ignition switch must be turned OFF between the 1st trip and 2nd trip).


      • Freeze frame data:

        Freeze frame data records the engine condition when malfunction is detected. Because freeze frame data records the engine conditions (fuel system, calculator load, engine coolant temperature, fuel trim, engine speed, vehicle speed, etc.) when the 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.

        Text in Illustration
        *1 DLC3
        *2 intelligent tester