DTC P0121 Throttle / Pedal Position Sensor / Switch "A" Circuit Range / Performance Problem
HINT: This DTC relates to the Throttle Position (TP) sensor.
DESCRIPTION Refer to DTC P0120
DTC No. |
DTC Detection Condition |
Trouble Area |
P0121 |
Difference between VTA1 and VTA2 voltages less than 0.8 V, or more than 1.6 V for 2 seconds (1 trip detection logic) | TP sensor (built into throttle body) |
MONITOR DESCRIPTION
The ECM uses the TP sensor to monitor the throttle valve opening angle.
This sensor transmits two signals: VTA1 and VTA2. VTA1 is used to detect the throttle opening angle and VTA2 is used to detect malfunctions in VTA1. The ECM performs several checks to confirm the proper operation of the TP sensor and VTA1.
For each throttle opening angle, a specific voltage difference is expected between the outputs of VTA1 and VTA2. If the voltage output difference between the two signals deviates from the normal operating range, the ECM interprets this as a malfunction of the TP sensor. The ECM illuminates the MIL and sets the DTC.
If the malfunction is not repaired successfully, the DTC is set 2 seconds after the engine is next started.
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
TYPICAL MALFUNCTION THRESHOLDS
FAIL-SAFE
When this DTC, as well as other DTCs relating to ETCS (Electronic Throttle Control System) malfunctions, is set, the ECM enters fail-safe mode. During fail-safe mode, the ECM cuts the current to the throttle actuator off, and the throttle valve is returned to a 6.5 throttle angle by 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 allow the vehicle to continue at a minimal speed. If the accelerator pedal is depressed slowly, the vehicle can be driven slowly.
Fail-safe mode continues until a pass condition is detected, and the ignition switch is then turned off.
INSPECTION PROCEDURE
HINT: Read freeze frame data using the intelligent tester. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air-fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction.
1 CHECK ANY OTHER DTC OUTPUT (IN ADDITION TO DTC P0121)
Result
HINT: If any DTCs other than P0121 are output, troubleshoot those DTCs first.
REPLACE THROTTLE BODY
Transmitter ID1 Error
DESCRIPTION
The tire pressure warning valve and transmitters that are installed in the
tire and wheel assemblies
measure the air pressure of the tires. The measured values are transmitted to
the tire pressure warning
antenna and receiver on the body as radio waves and then sent to the tir ...
Cranking Holding Function Circuit
DESCRIPTION
The system detects the ignition switch's starting signal (STSW) and then
supplies current to the starter
until the ECM judges that the engine has started successfully. The purpose is to
reduce the holding time
of the ignition key.
WIRING DIAGRAM
Refer to DTC P0617 (See page ...
Throttle Actuator Control Motor Current Range / Performance
DESCRIPTION
The ETCS (Electronic Throttle Control System) has a dedicated power supply
circuit. The voltage (+BM)
is monitored and when it is low (less than 4 V), the ECM determines that there
is a malfunction in the
ETCS and cuts off the current to the throttle actuator.
When the volt ...