Toyota Corolla (E120): Circuit description
When driving uphill under cruise control, in order to reduce the number of shifting due to on–off overdrive operation and to provide smooth driving, when down shifting in the electronically controlled transmission occurs, a signal to prevent upshift until the end of the uphill slope is sent from the cruise control ecu assy to the electronically controlled transmission.
Terminal ect of the cruise control ecu assy detects the shift change signal (output to electronically controlled transmission no.2 Solenoid) from the ecm.
If the vehicle slows down, also when terminal ect of the cruise control ecu assy receives down shifting signal, it sends a signal from terminal od to ecm to cut overdrive until the end of the uphill slope, and the number of gear shifts are reduced and gear shift points in the electronically controlled transmission are changed.
Wiring diagram

Other materials:
Inspection procedure
Hint:
if dtcs p0115, p0116, p0117, p0118 and p0125 are output
simultaneously, the engine coolant temperature
sensor circuit may be open or short. Perform the troubleshooting of dtc
p0115, p0117 or
p0118 first.
Read freeze frame data using the hand-held tester or the obd ii scan
to ...
Inspection procedure
Hint
Advanced timing over
(valve timing is out of specified range)
P0011
Retarded timing over
(valve timing is out of specified range)
P0012
If dtc p0011 or p0012 is displayed, check the vvt system circuit.
Read freeze frame data using the hand–held tester o ...
On–vehicle inspection
1. Inspect refrigerant pressure with manifold gauge set
this is a method in witch the trouble is located by using
a manifold gauge set. Read the manifold gauge pressure
when the these conditions are established.
Test conditions:
temperature at the air inlet with the switch set
...


