2.4LTE Fault Codes - Diagnosis & Clearing

 

Introduction to On Board Diagnostics
A number of components of modern motor vehicles are now controlled by computers electronics and this has lead to significant improvement of the performance and reliability.

However, once things go wrong, it can be a real nightmare. Most symptoms are often 'occasional symptoms', making the diagnosis very difficult. Moreover, certain symptoms can sometime disappear during the diagnosis process, in which case the cause will be unknown until it strikes again.

Of course, the use of oscilloscope or special inspection tools may come in handy for this sort of tasks but at the same time not all mechanics can have access to such equipment or facility.

Thus the engine management computer, which is often referred to as ECU (Engine Control Unit) comes with a feature which monitors the system network and when a fault is detected, it may switch to so-called 'safety mode' to guarantee safety as well as inform the driver as necessary and records the associated problem areas.

This is the OBD (On Board Diagnostic) system, the self-diagnosis system. The records of problem areas are stored as codes and this can be recalled by carrying out a particular procedure where a specific code is displayed by either flashing a warning light in certain intervals or by providing different voltage from the service socket etc.

This may seem a wonderful system which gives solutions to all problems. NOT! It should be noted that the OBD is never perfect and time to time, they do lie. The OBD may sometimes show the 'normal' code despite the fault is still present and visually evident. Also the OBD cannot detect every single fault on the car either.
Therefore, one should always be prepared that even if the 'normal' code is shown, the fault may still exist within the area outside the scope of the OBD.

Above all, cars still rely heavily on the mechanics who maintain them and nothing can be more precious than skills and experience.

Introduction to Toyota OBD
Toyota's OBD system is one of the most user-friendly and no major change has been made since the it was first introduced.

The design of service connectors may differ from model to model as well as year to year but the main procedures are mostly identical.
Early service sockets were round shaped and voltage meter had to be connected in order to obtain the code. The code was obtained by counting the number of times the voltage changes from 0 volts to 5 volts in given intervals.
However, modern service sockets are mostly square shaped and do not require a voltage meter. Instead it blinks the 'Check Engine' warning light.
Initially, codes were displayed in 1 digit figure, but as the OBD became capable of tracking more areas, it was no longer possible to cope with just 1 digit number thus most modern models display codes in 2 digits figure. Furthermore, some models are equipped with dual mode detection, which in addition to the ordinary diagnostic function, the system has a secondary mode which is capable of detecting instantaneous faults.

Obtaining the diagnostic code
There are two service connectors. One is located at various locations in the engine compartment depending on models, while the second one is located inside the car, usually below the driver's side dashboard and either of them can be used to carry out the test.


NORMAL MODE Testing
'NORMAL MODE' displays code(s) for the present faults as well as the faults occurred in the past.

1. Turn the ignition key to 'ON' position and make sure the 'Check Engine' warning lights on the dash board comes on.

2. Turn the ignition key to 'OFF' position.

3. Open the cover of the service socket located in the engine compartment.

4. Link the terminal marked TE1 and E1 together with a piece of wire.
Note: Terminals are often filled with grease to prevent corrosion and this sometimes creates difficulties seeing each terminal, hence care should be taken to ensure the right terminals are linked.

5. Turn the ignition key to "ON' position, but do not start the engine.

6. The 'Check Engine' warning light on the dash board should start to flash. The code can be obtained by counting the number of flashes.
If the 'Check Engine' warning light does not flash, the vehicle may be fitted with one of the early OBD systems which require a voltage meter to obtain the code. In such case, '+' probe of the voltage meter should be connected to terminal marked VF and '-' probe to E1 terminal and count the number of times the voltage moves between 0 to 5 volts.

7. With the number of flashes, it can be determined whether the system uses 1 digit code display or 2 digits code display.

8. The code differs from model to model but if the system is normal, code no. '1' will shown where the 'Check Engine' warning light blinks continuously. If there is a fault, there will be a pause between the blinks. The first set of blinks show the first digit of the code and second set of blinks after the pause indicates the second digit of the code. For instance, code '41' will blink 4 times in a row and pause, then it blinks once. If there was more than one code being stored in the ECU, it displays from the lower number and goes back to the beginning after displaying all the relevant codes.


TEST MODE Testing
'TEST MODE' is capable of detecting faults which cannot be detected under 'NORMAL MODE' described in previous section. This method can be used to track instantaneous faults such as loose connectors, as well as for test drive after a service to double check everything is in good order.

1. First of all, it is vital to check everything is fine under 'NORMAL MODE'. If there is a fault, it should be rectified before proceeding.

2. If the diagnostic codes which were previously stored under 'NORMAL MODE', they must be cancelled.

3. Pull the service socket located inside the car out. This is usually located under the driver's side dash board.

4. With the ignition key in 'OFF' position, link the terminal marked TE2 and E1 together with a piece of wire.

5. Turn the ignition key to 'ON' position and ensure the 'Check Engine' warning light on the dash board flashes.
Note: It is important that from this point onwards, the ignition key must never be switched back to 'OFF' position until the test is completed.

6. Turn the ignition key and start the engine. During this process, the starter motor signal is been checked. If the car was started other than using the ignition key, error code showing the 'Starter signal error' will be displayed.

7. Take the car to a test drive. During the test drive, the speed must exceed 5 km/h otherwise 'speed sensor' error will be recorded by the system.

8. After the test drive, stop the car but even at this point, the ignition key must never be switched back to 'OFF' position yet.

9. On the service socket located inside the car, link the terminal marked TE1 and E1 together using another piece of wire.

10. The code will be shown in the manner described in the previous section.

Note: At any time during the process, if the ignition key was accidentally switched back to 'OFF' position, the test has to be carried out from scratch since the code stored during 'TEST MODE' will be cancelled automatically whenever the ignition key is switched to 'OFF' position.

Cancelling the diagnostic code
The error codes stored in the ECU by the OBD will remain there until they are cancelled. Whenever a fault is rectified or a routine maintenance has been completed, it is vital to cancel the code.
For most vehicles, removing the EFI fuse for at least 10 seconds will cancel the code stored in the ECU. For certain cars with diesel engines, they may have a fuse named ECD or AM2 instead.
However, there are always few exceptions where codes cannot be cancelled in this manner. If this is the case, there should be a fuse named ECU so this should be removed to cancel the code. Alternatively, disconnecting the battery or ECU connector will undoubtedly cancel the code.

After cancelling the code, run the test again and double check to make sure they are actually cancelled. If they remain, either the cancellation procedures are incomplete or the fault area has not been rectified.

Cars with automatic gearbox
For certain models, automatic gearbox management system is built-in into the ECU. For these models, the OBD will also check the automatic gearbox system when the test is carried out. However, OBD for automatics will flash 'O/D OFF' warning light instead of the 'Check Engine' warning light.

Hence, if during the test, the 'O/D OFF' warning light starts to flash, it means that the automatic system is also being checked. The method of obtaining the code is the same as described earlier and necessary action should be taken according to the result.


RESULTS FROM CODES

1 - Normal
2 - Turbo boost pressure sensor
4 - Coolant temperature sensor
5 - Correction resistance (Pump)
6 - Pump speed sensor (Pump)
7 - Throttle position sensor
8 - Intake air temperature sensor
9 - Vehicle speed sensor
10 - Starter switch
11 - Switch sign (Vehicle not in P or N or A/C on)
12 - Timer control valve (Pump)
13 - Crank position sensor

To clear any codes either disconnect the battery or remove the ECD relay for one minute