Exhaust Gas RECIRCULATION (EGR)
- Connect ISAT Scan tester according to manufacturer's instructions. Diagnostic connector is under right front seat, protected by a plastic cover. Turn ignition on. Enter command code 555. Listen for sound of modulation valve, located forward of left front wheel housing. If there is sound from valve, go to step 5). If there is no sound, go to step 2).
- Turn ignition off. Unplug connector from modulation valve. Measure resistance between modulation valve terminals. If resistance is not about 30 ohms, replace valve.
- Turn ignition on. Check for battery voltage at Green/White wire on modulation valve harness connector. If no voltage, repair Green/White and/or Blue/Red wires to pin No. 87 of fuel injection relay.
- With ignition off, unplug fuel injection ECU. Check White and Yellow/White leads between modulation valve harness connector and ECU for open or short circuit. If valve and wiring are okay, replace fuel injection ECU.
- Reconnect wiring to modulation valve and fuel injection ECU. Locate EGR temperature sensor. Temperature sensor is integral with EGR valve, located on intake manifold. Unplug connector from EGR temperature sensor.
- Start engine. With engine idling, measure resistance between EGR sensor terminals. Resistance should be several megohms. Apply vacuum to valve by connecting vacuum pump to Red-marked hose. Sensor resistance should drop to several thousand ohms. Replace EGR valve if resistance is not as specified.
- With ignition off, unplug fuel injection ECU connector. Check Yellow/White wire between EGR temperature sensor and fuel injector ECU terminal No. 23 for open or short to ground. Check Black wire between temperature sensor and ground.
- If fault persists, disconnect Red-marked hose from modulation valve. Apply vacuum to hose. If engine RPM drops, EGR valve is okay. If not, check hoses, connections, and vacuum tank.