Toyota Tacoma manuals

Toyota Corolla Repair Manual: 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 valve is closed at 0 km/h
  • Throttle position sensor (built in throttle body)

Monitor description

The throttle position sensor varies its resistance with the angle of the throttle valve. The ecm applies a regulated reference voltage to the throttle position sensor + terminal and calculates the angle of the throttle valve based on the voltage present at the throttle position sensor signal terminal.

When the throttle valve is near the fully closed position, the output voltage of the throttle position sensor is low. When it is near the fully open position, the output voltage is high.

The ecm checks the indicated angle of the throttle valve during stop and go conditions. If the indicated angle (or voltage) in the closed throttle position is out of the specified range, the ecm interprets this as a malfunction in the throttle position sensor and sets a dtc.

Monitor strategy

Typical enabling condition

Typical enabling condition

Stop and go is defined as follows:

Stop and go is defined as follows: stop indicates a vehicle speed of 0 mph (0 km/h). Go indicates a vehicle speed of 18.6 Mph (30 km/h).

Typical malfunction thresholds

Component operating range

Component operating range

Inspection procedure

Throttle/pedal position sensor/switch a circuit range/performance problem
Dtc p0121 throttle/pedal position sensor/switch a circuit range/performance problem Hint: this is the purpose of the throttle position sensor. ...

Inspection procedure
Hint: read freeze frame data using the hand-held tester or the obd ii scan tool. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, it is usefu ...

Other materials:

Inspection
1. Intake air flow meter subassy Inspect the intake air flow meter resistance.  Using an ohmmeter, measure the resistance between terminals tha and e2. Resistance: at 20 c (4 f) 13.6 To 18.4 KΩ at 20 c (68 f) 2.21 To 2.69 KΩ at 60 c (140 f) 0.49 To 0.67 KΩ ...

Inspection procedure
1 Inspect transmission wire(slt) Disconnect the transmission wire connector from the transaxle. measure the resistance according to the value(s) in the table below. Standard: Measure the resistance according to the value(s) in the table below. Standard (check for short): ...

Inspection
1. Cooling fan relay Inspect the cooling fan relay continuity.  Using an ohmmeter, check that there is continuity between terminals 1 and 2. If there is no continuity, replace the relay.  Check that there is no continuity between terminals 3 and 5. If there is conti ...

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