DTC P0121 Throttle / Pedal Position Sensor / Switch "A" Circuit Range / Performance Problem: Fail-Safe

When this DTC, as well as other DTCs relating to ETCS (Electronic Throttle Control System) malfunctions, is set, the ECM (Included in HV Control ECU) 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° 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 engine switch is then turned to off.

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 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.

1. CHECK OTHER DTC OUTPUT (IN ADDITION TO DTC P0121) 
   1. Connect the intelligent tester to the DLC3.
   2. Turn the ignition switch ON.
   3. Turn the tester ON.
   4. Enter the following menus: DIAGNOSIS / ENHANCED II / DTC INFO / CURRENT CODES.
   5. Read the DTC.

      Result 

      RESULT CHART
      
      

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

   B: GO TO  DIAGNOSTIC TROUBLE CODE CHART  

   A: REPLACE THROTTLE BODY ASSEMBLY