Toyota Mark2 GX110 Check Lamp Lit

20001 Toyota Mark2 GX110 Engine Model 1G

Situation
Engine check lamp illuminated.
The engine was hunting a liittle at an idle.

Cause
Faulty throttle position sensor.

Maintenance
Diagnosis noticed that cord P0120 which meant throttle sensor systems.
I used a service manual and confirmed by data monitor.
Then I checked throttle sensor of accelration angle and idling switch.
The throttle sensor was 0% (Faulty)
The idling switch was off (faulty)
After that I took off the throttle position sensor and checked it.
It was disconnecting at ON.(Faulty)
Then I judged that it had been faulty and exchanged new throttle position sensor.