Toyota Corolla (E120) 2002–2008 Repair Manual / Introduction / How to troubleshoot ecu controlled
systems / How to proceed with troubleshooting
Toyota Corolla (E120): How to proceed with troubleshooting
Hint
: carry out troubleshooting in accordance with the procedures on the following page. Here, only the basic procedures are shown. Details are provided in the diagnostics section, showing the most effective methods for each circuit. Confirm the troubleshooting procedures first for the relevant circuit before beginning troubleshooting of that circuit.
1 Vehicle brought to workshop

2 Customer problem analysis
- ask the customer about the conditions and environment when the problem occurred.

- Check the battery positive voltage.
Voltage: 11 – 14 v (engine stopped)
- visually check the wire harness, connectors and fuses for open and short, etc.
- warm up the engine to the normal operating temperature.
- confirm the problem symptoms and conditions, and check for dtcs according to the related chart.
Ok go to step 5

4 Dtc chart
- Check the results obtained in step 3, then confirm the inspection procedures for the system or the part which should be checked using the dtc chart.
Go to step 6
5 Problem symptoms chart
- Check the results obtained in step 3, then confirm the inspection procedures for the system or the part which should be checked using the problem symptoms table.

6 Circuit inspection or parts inspection
- Confirm the circuit for the system or the part which should be checked using the problem symptoms table or the results obtained in step 4.

7 Repair
- Repair the affected system or part in accordance with the instructions in step 6.

8 Confirmation test
- After completing repairs, confirm that the problem has been solved (if the problem does not recur, perform a confirmation test under the same conditions and in the same environment as when it occurred for the first time).

End
Other materials:
Sound quality is bad in all modes (volume is too low)
Wiring diagram
Inspection procedure
1 Adjust sound quality
Adjust the sound quality.
Operate the radio receiver assy to adjust the sound quality.
Standard: malfunction disappear.
2 Compare it with another car of same model
Compare it with another vehicle of the same mo ...
Circuit description
Refer to dtc p0120
Dtc no.
Dtc detection condition
Trouble area
P0121
The following condition is met 4 times. After the vehicle speed
has exceeded 19 mph (30 km/h) once, the throttle position
sensor output value is out of normal range when the throttle
...
Definition of terms
Term
Definition
Monitor description
Description of what the ecm monitors and how it detects malfunctions
(monitoring purpose and its details).
Related dtcs
Diagnostic code
Typical enabling condition
Preconditions that allow the ecm to detect ...


