| WARNING | Read service precautions before proceeding with service procedure. See SERVICE PRECAUTIONS . |
| CAUTION | If Engine Control Module (ECM) replacement is instructed in following test, always ensure ECM electrical connectors and ground circuits are okay. If either are defective, repair and repeat testing to confirm ECM malfunction. |
Note. If DTCs P0110, P0115, P0120 and P0450 are output simultaneously, the E2 sensor ground circuit at terminal No. 18 (Brown wire) at ECM electrical connector E8 may be open. See WIRING DIAGRAMS article. For ECM electrical connector terminal identification (Схема №7) It may be necessary to check Brown wire between splice I7 and terminal No. 18 at ECM electrical connector E8. Splice I7 is located behind passenger's side of instrument panel. (Схема №10)
Circuit Description
Throttle Position (TP) sensor uses 2 sensors which detects throttle opening and a malfunction of the TP sensor. TP sensor is located on throttle body and provides an input voltage of 0-5 volts to VTA and VTA2 terminals at ECM in proportion to throttle opening. ECM uses input signals and controls the throttle control motor to provide proper throttle valve opening in response to driving conditions. DTC is set when improper input signals from TP sensor are received at ECM. If DTC P0120 exists, ECM will operate in fail-safe mode which turns off power to throttle control motor and throttle valve is closed by the return spring. Possible causes are
- TP sensor circuit is open or shorted.
- Defective TP sensor.
- Defective ECM.
Diagnostic Aids
After confirming DTC P0120, use Toyota hand-held tester or scan tool to access CURRENT DATA to read accelerator pedal opening position percentage and voltage by reading THROTTLE POS (displayed as a percentage) and THROTTLE POS#2 (displayed as a voltage) to determine probable cause. See ACCELERATOR PEDAL OPENING POSITION SPECIFICATIONS table. Using hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected.
| Condition & Throttle Position Reading | Probable Cause | |
|---|---|---|
| Accelerator Pedal Released | ||
| Throttle Pos (0%) & Throttle Pos#2 (0 Volts) | Open In VC Circuit | |
| Throttle Pos (0%) & Throttle Pos#2 (2.0-2.9 Volts) | Open Or Short To Ground In VTA Circuit | |
| Throttle Pos (8-20%) & Throttle Pos#2 (0 Volts) | Open Or Short To Ground In VTA2 Circuit | |
| Throttle Pos (100%) & Throttle Pos#2 (5 Volts) | Open In E2 Circuit | |
| Accelerator Pedal Depressed | ||
| Throttle Pos (0%) & Throttle Pos#2 (0 Volts) | Open In VC Circuit | |
| Throttle Pos (0%) & Throttle Pos#2 (4.6-5.1 Volts) | Open Or Short To Ground In VTA Circuit | |
| Throttle Pos (64-96%) & Throttle Pos#2 (0 Volts) | Open Or Short To Ground In VTA2 Circuit | |
| Throttle Pos (100%) & Throttle Pos#2 (5 Volts) | Open In E2 Circuit | |
ACCELERATOR PEDAL OPENING POSITION SPECIFICATIONS