2UZ-FE ENGINE CONTROL: SFI SYSTEM: CAUTION / NOTICE / HINT (2008 Sequoia)

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 output voltage 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 stores the DTC.

If the malfunction is not repaired successfully, the DTC is stored 2 seconds after the engine is next started.

MONITOR STRATEGY

Related DTCs

P0121: TP sensor rationality

Required Sensors/Components (Main)

TP sensor

Required Sensors/Components (Related)

Frequency of Operation

Continuous

Duration

Within 2 seconds

MIL Operation

Immediate

Sequence of Operation

None

TYPICAL ENABLING CONDITIONS

Monitor runs whenever following DTCs not present

None

Either of following conditions A or B set

A. Ignition switch

B. Electric throttle motor power

TYPICAL MALFUNCTION THRESHOLDS

Difference in voltage between VTA1 and VTA2

TP sensor 1 - [TP sensor 2 x 0.8 (corrected by learning value)]

Less than 0.8 V, or more than 1.6 V

FAIL-SAFE

When this DTC, as well as other DTCs relating to ETCS (Electronic Throttle Control System) malfunctions, is stored, the ECM enters fail-safe mode. During fail-safe mode, the ECM cuts the current to the throttle actuator, and the throttle valve is returned to a 7° 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 firmly and gently, 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:

This DTC relates to the Throttle Position (TP) sensor.
Read freeze frame data using the Techstream. Freeze frame data records the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, 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.

Result

Proceed to

P0121 is output

P0121 and other DTCs are output