Diagnosis & Repair (Using Toyota Scan Tool)
- Connect scan tool. See Figure. Start and run engine. Allow engine to reach normal operating temperature. Using scan tool, read EGR gas temperature. If temperature is 50-302°F (10-150°C), go to step 5). If temperature is not 50-302°F (10-150°C), go to next step.NOTE: If EGR gas temperature reading is 37.6°F (3.1°C), an open exists in EGR temperature sensor circuit. If temperature reading is 318.7°F (159.3°C), a short exists in EGR temperature sensor circuit.
- Disconnect EGR temperature sensor connector. Sensor is mounted in manifold running from EGR valve to intake manifold. Connect a jumper wire between EGR temperature sensor connector terminals. Turn ignition on. If EGR temperature displayed is not 318.7°F (159.3°C), remove jumper wire and go to next step. If temperature displayed is 318.7°F (159.3°C), remove jumper wire. Recheck EGR temperature. If EGR temperature displayed is not 37.6°F (3.1°C), go to step 4). If temperature displayed is 37.6°F (3.1°C), check temperature sensor connector terminals. Repair as necessary. If connector is okay, replace sensor and retest.
- Turn ignition off. Access ECM behind glove box. Connect jumper wire between terminal No. 14 (Green/Red wire) at ECM E6 connector and terminal No. 22 (Brown wire) at ECM E7 connector. See Figure. Turn ignition on. If EGR temperature displayed is not 318.7°F ( 159.3°C), check ECM connectors. Repair as necessary and retest. If connectors are okay, replace ECM and retest. If temperature displayed is 318.7°F (159.3°C), locate and repair open in wiring harness between ECM and EGR temperature sensor.
- Remove jumper wire. Recheck EGR temperature. If EGR temperature displayed is not 37.6°F (3.1°C), check ECM connectors and repair as necessary. If connectors are okay, replace ECM and retest. If temperature displayed is 37.6°F (3.1°C), locate and repair short in wiring harness between ECM and EGR temperature sensor.
- Check vacuum hoses. See appropriate illustration in VACUUM DIAGRAMS article. Repair vacuum hoses as necessary. If all hoses are okay, check VSV. Using scan tool, select ACTIVE TEST mode. Check operation of VSV when activated by scan tool. VSV is located under "V" bank cover on top of engine.
- Start and run engine. With EGR system off, air from port "E" should flow from port "G". See Fig 1. With EGR system on, air from port "E". should flow from port "F". If valve operates as specified, go to step 8). If valve does not operate as specified, go to next step.
- Remove EGR VSV. Using ohmmeter, measure resistance between VSV terminals. Resistance should be 27-33 ohms at 68°F (20°C). Measure resistance between each terminal and body of VSV. Resistance should be infinite. If resistance is not as specified, replace VSV. If resistance is as specified, go to next step.
- Check VSV operation. Apply battery voltage to VSV terminals. Apply air pressure to VSV port "E". Air should flow from port "F". Remove battery voltage from valve terminals. Air should flow from port "G". Replace VSV as necessary. If VSV meets all specifications in steps 6) and 7), check for open in EGR VSV circuits between fuse block and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
- Disconnect vacuum hose from EGR valve. Connect a vacuum pump to EGR valve. Start engine. Apply vacuum to EGR valve. If engine does not run rough or stall, replace EGR valve and retest. If engine runs rough or stalls, check EGR Vacuum Control Valve (VCV). See SYSTEM/COMPONENT TESTS article. Replace as necessary. If VCV is okay, replace ECM and retest.