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Toyota Corolla Repair Manual: Diagnosis system

  1. Description
  1.  when troubleshooting obd ii vehicles, the only difference from the usual troubleshooting procedure is that you need to connect an obd ii scan tool complying with sae j1987 or a handheld tester to the vehicle, and read off various data output from the vehicles ecm.

  1. Obd ii regulations require that the vehicles on board computer illuminate the malfunction indicator lamp (mil) on the instrument panel when the computer detects a malfunction in the computer itself or in the drive system components which affect the vehicle emissions. In addition to the mil illuminating when a malfunction is detected, the applicable dtcs prescribed by sae j2012 are recorded in the ecm memory .

    If the malfunction does not occur in 3 consecutive trips, the mil goes off but the dtcs remain in the ecm memory.

  2.  To check the dtcs, connect the obd ii scan tool or handheld tester to the dlc3 of the vehicle. The obd ii scan tool or handheld tester also enables you to erase the dtcs and check freeze frame data and various forms of engine data (for instruction book).
  3.  The dtcs include 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 chart on page 05372).
  4. The diagnosis system operates in the normal mode during the normal vehicle use, and also has a check mode for technicians to simulate malfunction symptoms and perform troubleshooting. Most dtcs use 2 trip detection logic(*) to prevent erroneous detection.

    By switching the ecm to the check mode when troubleshooting, the technician can cause the mil to illuminate for a malfunction that is only detected once or momentarily. (Handheld tester).

  5.  *2 Trip detection logic: when a malfunction is first detected, the malfunction is temporarily stored in the ecm memory. If the same malfunction is detected again during the second test drive, this second detection causes the mil to illuminate.

  1. Inspect the dlc3.

    The vehicles ecm uses iso 91412 for communication.

    The terminal arrangement of dlc3 complies with sae j1962 and matches the iso 91412 format.

Hint:

Hint

: if your display shows unable to connect to vehicle when you have connected the cable of the obd ii scan tool or handheld tester to the dlc3, turned the ignition switch to the on position and operated the scan tool, there is a problem on the vehicle side or tool side.

  1.  measure the battery voltage.

    Battery voltage: 11 to 14 v if voltage is below 11 v, recharge the battery before proceeding.

  2.  check the mil.
  1.  The mil comes on when the ignition switch is turned to the on position and the engine is not running.

    Hint

    : if the mil does not light up, troubleshoot the combination meter.

  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.

Customer problem analysis check
Location ...

Dtc check/clear
1. Dtc check (normal mode) Notice: handheld tester only: when the diagnostic system is switched from the normal mode to the check mode, all the dtcs and freeze frame data recorded in the normal ...

Other materials:

Malfunction in water temperature receiver gauge
Wiring diagram Inspection procedure 1 Read value of handheld tester Check output value of ecm.  Connect the handheld tester to dlc3.  Turn the ignition switch to on and push the handheld tester main switch on.  Select the data list mode on the handheld teste ...

Onvehicle inspection
1. Inspection throttle body idle speed control valve assy Notice: it is impossible to check the resister value and the operation of isc valve by itself, because the isc valve has an ic circuit inside it, which transforms the duty signal from the ecm to the derive signal. After check ...

Ecm/pcm processor
Dtc p0606 ecm/pcm processor Monitor description The ecm continuously monitors its internal circuits. This selfcheck insures that the ecm is functioning properly. If a malfunction is detected, the ecm will set the appropriate dtc and illuminate the mil. The two cpus, main and sub cpu ins ...

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