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:
On–vehicle inspection
1. Check battery electrolyte level
Check the electrolyte quantity of each cell (maintenance–free battery).
If under the lower level, replace the battery (or add distilled
water if possible) and check the charging
system.
check the electrolyte quantity of each cell ...
Circuit description
The rotary solenoid type idle air control (iac) valve is located
under the throttle body and intake air bypassing the throttle
valve flows into the iac valve through the passage.
In this way the intake air volume bypassing the throttle valve is
regulated, controls the engine speed.
The ...
Circuit description
The seat belt buckle switch (lh) circuit consists of the airbag sensor assy
center and front seat inner belt
assy (lh).
Dtc b0126/b0127/27 is recorded when a malfunction is detected in the seat belt
buckle switch (lh) circuit.
Wiring diagram
...


