| 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. If ECM is replaced, ECM must be programmed with proper ignition key code for engine immobilizer system. For programming procedures, see COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION, or appropriate ENGINE IMMOBILIZER SYSTEMS article in ACCESSORIES & EQUIPMENT. |
Circuit Description
Electronic Throttle Control System (ETCS) uses throttle control motor to operate throttle valve. Throttle valve opening is detected by Throttle Position (TP) sensor which delivers input signals to ECM. ECM uses input signals and controls the throttle control motor to provide proper throttle valve opening in response to driving conditions. DTC is set if a throttle control motor current or output duty is not within specified range. If DTC P1125 exists, ECM will turn off the power to throttle control motor and throttle valve is closed by the return spring. When this occurs, throttle valve is controlled by throttle cable connected to accelerator pedal. Possible causes are
- Throttle control motor circuit is open or shorted.
- Defective throttle control motor.
- Defective ECM.
Diagnostic Aids
Using Toyota hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected.
Scheme 66
Scheme 67
- Remove glove box and heater duct (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Waveform pattern should be checked for throttle control motor M+ and M- circuits at ECM. Connect oscilloscope between terminal No. 17 (Brown wire) at ECM electrical connector E7 and No. 7 (Pink wire; M- circuit) or No. 8 (Violet wire; M+ circuit) at ECM electrical connector E8. This is the E1, M- and M+ terminals on ECM. For ECM electrical connector terminal identification see scheme 4 Start engine and allow engine to idle. Note M- and M+ waveform pattern with engine idling. Ensure M- and M+ waveform patterns are properly displayed. (Scheme 66) Ensure engine is idling when checking waveform pattern, as waveform pattern will change with throttle opening. If any waveform pattern is not as shown, shut engine off. Go to next step. If both waveform patterns are as shown, shut engine off. Replace ECM.
- Disconnect electrical connector at throttle control motor located on side of throttle body. (Scheme 67) Using ohmmeter, check resistance between terminals No. 1 and 2 on electrical connector on throttle control motor. (Scheme 67) Resistance should be.3-100.0 ohms at 68°F (20°C). If resistance is within specification, go to next step. If resistance is not within specification, replace throttle control motor. See «THROTTLE BODY»(ref-133227-S01273866582002021900000) under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.
- Check for open and short in Pink and Violet wires and electrical connectors between throttle control motor and ECM. See «WIRING DIAGRAMS»(ref-133228) article. If wiring harness and electrical connectors are okay, replace ECM. If wiring harness or electrical connector is defective, repair as necessary.