| 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
Magnetic clutch is located between throttle control motor and throttle body. Throttle motor opens and closes throttle valve by using the magnetic clutch. DTC is set if magnetic clutch current is not within specified range. If DTC P1126 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
- Magnetic clutch circuit is open or shorted.
- Defective magnetic clutch.
- 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 68
- If Toyota hand-held tester is available, go to next step. If Toyota hand-held tester is not available, go to step 3.
- Connect hand-held tester to Data Link Connector (DLC) No. 3 at driver's side of instrument panel. see scheme 1 Turn ignition on and then turn hand-held tester on. Using hand-held tester, read magnetic clutch current value. If magnetic clutch current is.8-1.0 amp, go to step 4. If magnetic clutch current reading is not.8-1.0 amp, go to step 6.
- 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 magnetic clutch at ECM. Connect oscilloscope between terminal No. 19 (Blue/White wire; CL- circuit) and No. 29 (Blue/Black wire; CL+ circuit) at ECM electrical connector E8. For ECM electrical connector terminal identification see scheme 4 Start engine and allow engine to idle. Note magnetic clutch waveform pattern with engine idling. Ensure magnetic clutch waveform pattern is properly displayed. (Scheme 68) If magnetic clutch waveform pattern is as shown, go to next step. If magnetic clutch waveform pattern is not as shown, go to step 6.
- Disconnect electrical connector at throttle control motor located on side of throttle body. see scheme 22 Using ohmmeter, check resistance between terminals No. 3 and 4 on electrical connector on throttle control motor for the magnetic clutch. see scheme 22 Resistance should be 4.2-5.2 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 with magnetic clutch as an assembly. See «THROTTLE BODY»(ref-133227-S01273866582002021900000) under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.
- Check for open and short in Blue/White and Blue/Black wires and electrical connectors between throttle control motor and ECM. See «WIRING DIAGRAMS»(ref-133228) article. If wiring harness and electrical connectors are okay, go to next step. If wiring harness or electrical connector is defective, repair as necessary.
- Using Toyota hand-held tester or scan tool, clear DTCs from ECM. Start engine and allow engine to idle. Turn ignition off and wait 3 seconds. Turn ignition on and then use Toyota hand-held tester or scan tool to check for DTCs. If DTC P1126 does not exist, replace ECM. ECM is located behind glove box and heater duct. see scheme 2 If DTC P1126 exists, replace throttle control motor with magnetic clutch as an assembly. See «THROTTLE BODY»(ref-133227-S01273866582002021900000) under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.