EGR Control Valve Check
- On Maxima and 300ZX models, warm up engine. Check movement of EGR valve diaphragm by keeping engine speed between 900 RPM and 3200 RPM. With engine cold, diaphragm should not move. While engine is hot, diaphragm should move upwards. If not okay, go to step 3). If okay, go to next step.
- Check EGR valve for operation. The EGR control solenoid should be on, and the EGR system should be off under the following conditions: engine starting; throttle valve switch on; low engine temperature; high engine temperature; engine speed below 900 RPM and above 3200 RPM. If okay, end test. If not okay, check the throttle valve switch, cylinder head temperature sensor, ignition signal, and the starting system.
- Check EGR vacuum. Disconnect vacuum hose at EGR valve. Check if a vacuum appears when keeping engine speed at 900 RPM to 3200 RPM. Stop engine. If not okay, go to next step. If okay, check EGR control valve. Apply 3.94-4.33 in. Hg of vacuum to the EGR control valve. The valve should be fully open. If okay, restart inspection, if not, replace EGR valve, and start test again.
- Check vacuum hose for proper connection, distortion, plugging, or breaks. If not okay, replace. If okay, check solenoid valve. Check EGR control solenoid valve for continuity. Resistance at the valve connector should be approximately 30 ohms. Check EGR control solenoid for operation. See Fig 1 . If not okay, replace EGR control solenoid valve. If okay, check battery voltage.
- Disconnect EGR control solenoid valve harness connector and check voltage with ignition switch in the "ON" position. Voltage at connector should be zero volts when ignition switch is in the "OFF" position, and 12 volts when switch is turned to the "ON" position. If not okay, check harness between the solenoid and ECU, and battery source for ECU. Refer to BATTERY SOURCE & GROUND test. If okay, check harness between ECU terminal No. 4 and the solenoid valve.
- Disconnect ECU 20-pin connector, and check for continuity between terminal No. 4 and ground while jumping EGR control solenoid harness connector to ground. See Fig 1 . Resistance should be zero ohms. If not okay, repair or replace solenoid harness. If okay, check throttle valve switch, cylinder head temperature sensor, ignition signal and starting system. If okay, replace ECU.