Toyota Corolla (E120): Check and replace ecu
Notice
: start an inspection of the connector from the backside of the connector on the wire harness side with the connector connected to the ecu.
When no measurement condition is specified, perform the inspection with the engine stopped and also the ignition switch on.
- First check the ecu ground circuit. If it is faulty, repair it.
If it is normal, the ecu could be faulty. In this case, replace the ecu with one that functions normally and check if the symptoms appear.
- Measure the resistance between the ecu ground
terminal and body ground.
Resistance: 1 Ω or less

- Disconnect the ecu connector, check the ground terminals on the ecu side and wire harness side for bends and check the contact pressure.

Other materials:
Circuit description
The fuel trim is related to the feedback compensation value, not to the basic
injection time. The fuel trim includes
the short–term fuel trim and the long–term fuel trim.
The short–term fuel trim is the short–term fuel compensation used to maintain
the air–fuel ratio at stoichiomet ...
Key confinement prevention function does not work
properly (unlock warning switch circuit)
Circuit description
The unlock warning switch turns on when the key is inserted in the ignition
key cylinder and the door courtesy
switch turns on when the driver’s door is opened, and the integration relay
monitors both switches conditions.
According to these switches conditions, the int ...
Light control switch circuit
Wiring diagram
Inspection procedure
1 Check headlamp dimmer switch assy (light control switch)
2 Check wire harness (tvip ecu light control switch)
Disconnect the tvip ecu and light control switch connectors.
check the continuity between the terminals of the tvip
e ...


