| CAUTION | If ECM replacement is instructed in following testing, always ensure ECM connectors and ground circuits are okay. If either are defective, repair and repeat testing to confirm ECM malfunction. If ECM is replaced, ECM must be programmed with proper ignition key code for engine immobilizer system. For programming procedures, see COMPUTER RELEARN PROCEDURES - IMPORT article in GENERAL INFORMATION, or appropriate ENGINE IMMOBILIZER SYSTEMS article in ACCESSORIES & EQUIPMENT. |
Note. If DTCs P0100, P0101, P0110, P0115 and P0120 are output together, check circuit E2 (White wire) between terminal No. 18 at ECM harness connector E8 and splice E7. Repair as necessary. See WIRING DIAGRAMS article.
Note. For component location, see appropriate illustration in THEORY & OPERATION article.
Circuit Description
Throttle Position (TP) sensor is a variable resistor mounted to throttle body which detects throttle opening angle. ECM determines vehicle driving condition 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 use scan tool to access CURRENT DATA to confirm throttle valve opening percentage with throttle open and closed. If percentage displayed on scan tool is always zero percent, VC circuit may be open or VTA circuit may be open or shorted. If percentage displayed on scan tool is always 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.