Toyota Corolla Repair Manual: Diagnosis system
- Description
- 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 hand–held tester to the
vehicle, and read off various data output from the
vehicle’s ecm.

- Obd ii regulations require that the vehicle’s 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.
- To check the dtcs, connect the obd ii scan tool or
hand–held tester to the dlc3 of the vehicle. The
obd ii scan tool or hand–held tester also enables
you to erase the dtcs and check freeze frame data
and various forms of engine data (for instruction
book).
- 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 05–372).
- 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. (Hand–held tester).
- *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.

- Inspect the dlc3.
The vehicle’s ecm uses iso 9141–2 for communication.
The terminal arrangement of dlc3 complies with sae
j1962 and matches the iso 9141–2 format.

Hint
:
if your display shows unable to connect to vehicle
when you have connected the cable of the obd ii scan tool or
hand–held 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.
- 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.
- measure the battery voltage.
Battery voltage: 11 to 14 v
if voltage is below 11 v, recharge the battery before proceeding.
- check the mil.
- 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.
- 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.
1. Dtc check (normal mode)
Notice:
hand–held 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:
Washer fluid
Add washer fluid in the following situations:
● A washer does not work.
● Vehicles without a multi-information display: The low windshield washer fluid
warning light (if equipped) comes on.
● Vehicles with a multi-information display: The warning message (if equipped) appear ...
Stopping the engine
1 Stop the vehicle.
2 Continuously variable transmission: Shift the shift lever to P.
Manual transmission: Shift the shift lever to N.
3 Set the parking brake. 4 Press the engine switch.
5 Vehicles without a multi-information display: Release the brake pedal (continuously
variable transmission ...
Adjustment
1. Put vehicle these conditions
tire inflation pressure is the specified value .
start the engine.
2. Adjust fog light aim
The fog light aim can be adjusting by moving the aiming
screw in the vertical direction.
Hint:
the optical aim moves upward when turning a scr ...
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