DTC    P0121    Throttle / Pedal Position Sensor / Switch "A" Circuit Range / Performance Problem

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DESCRIPTION

HINT:
  1. This Electronic Throttle Control System (ETCS) does not use a throttle cable.
  2. This throttle position sensor is a non-contact type.

The throttle position sensor is mounted on the throttle body and it detects the opening angle of the throttle valve. This sensor is electronically controlled and uses Hall-effect elements so that accurate control and reliability can be obtained. The throttle position sensor has 2 sensor elements VTA and VTA2, each with their own signal outputs. VTA is used to detect the throttle opening angle and VTA2 is used to detect malfunctions in VTA. Voltage applied to VTA and VTA2 changes between 0 V to 5 V in proportion to the opening angle of the throttle valve. There are several checks that the ECM performs to confirm proper operation of the throttle position sensor.
The ECM judges the current opening angle of the throttle valve from these signals input from terminals VTA and VTA2, and the ECM controls the throttle actuator to set the throttle valve angle properly in response to driver inputs.

A019802E14


DTC No.
DTC Detection Condition
Trouble Area
P0121
Difference between VTA and VTA2 voltage deviates from the malfunction criteria (for 2 seconds) (1 trip detection logic)
  1. Throttle position sensor
  1. ECM

MONITOR DESCRIPTION

The ECM uses the throttle position sensor to monitor the throttle valve opening angle.
This sensor includes 2 signals: VTA and VTA2. VTA is used to detect the throttle opening angle and VTA2 is used to detect malfunctions in VTA. There are several checks that the ECM performs to confirm proper operation of the throttle position sensor and VTA.
There is a specific voltage difference expected between VTA and VTA2 for each throttle opening angle.
If the output voltage difference of the VTA and VTA2 deviates from the normal operating range, the ECM interprets this as a malfunction of the throttle position sensor. The ECM will illuminate the MIL and set a DTC. This monitor runs for 2 seconds (the first 2 seconds of engine idle) after the engine is started (1 trip detection logic).

FAIL-SAFE

If the ETCS has a malfunction, the ECM cuts off current to the throttle actuator. The throttle valve returns to a predetermined opening angle (approximately 16°) by the force of the return spring. The ECM then adjusts the engine output by controlling the fuel injection (intermittent fuel-cut) and ignition timing in accordance with the accelerator pedal opening angle to enable the vehicle to continue at a minimal speed.
If the accelerator pedal is depressed firmly and slowly, the vehicle can be driven slowly.
If a "pass" condition is detected and then the engine switch is turned off, the fail-safe operation will stop and the system will return to normal.

WIRING DIAGRAM


A085458E05


INSPECTION PROCEDURE

HINT:
  1. Read freeze frame data using the intelligent tester. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, if the engine was warmed up or not, if the air-fuel ratio was LEAN or RICH, and other data from the time the malfunction occurred.
  2. This is the repair procedure for the throttle position sensor.

1.READ OTHER DTC OUTPUT (IN ADDITION TO DTC P0121)

Result:

Display (DTC output)
Proceed to
P0121
A
P0121 and other DTCs
B

HINT:
If any other codes besides P0121 are output, perform troubleshooting for those codes first.



B
GO TO RELEVANT DTC CHART
A

REPLACE THROTTLE BODY