| 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 and P0120 are output simultaneously, the E2 sensor ground circuit at terminal No. 18 (Green/White wire) at ECM electrical connector E6 may be open. See WIRING DIAGRAMS article. For ECM electrical connector terminal identification (Схема №4) It may be necessary to check Green/White wire between splice I13 and terminal No. 18 at ECM electrical connector E6. Splice I13 is located behind passenger's side of instrument panel. (Схема №6)
Circuit Description
Throttle Position (TP) sensor is a variable resistor located on throttle body which monitors throttle opening and delivers input signal to VTA terminal on ECM. Input signal is about .3-1.0 volt with throttle fully closed and about 2.7-5.2 volts with throttle fully open. ECM uses input signal for determining vehicle driving conditions and adjusts air/fuel mixture accordingly. DTC is set when ECM consistently detects less than .1 volt or more than 4.9 volts on VTA circuit. If DTC P0120 exists, ECM will operate in fail-safe mode. 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 confirm throttle valve opening percentage with throttle fully closed and fully open to determine probable cause. If percentage displayed is always zero percent, VC circuit may be open or VTA circuit may be open or shorted. If percentage displayed is always approximately 100 percent, E2 circuit may be open. Using hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected.