EFI Models
- Check self-diagnostic light No. 12. If light is on, check No. 10 and No. 16 vacuum hoses for loose connection, before proceeding with test. Start engine and warm-up to normal operating temperature (cooling fan comes on).
- Disconnect vacuum hose from top of EGR valve. Connect vacuum pump/gauge to EGR valve. Plug EGR solenoid valve lower hose in No. 2 control box. Measure vacuum at idle. If vacuum reading stabilizes at 5.9-9.8 in. Hg, constant vacuum control valve is okay.
- If vacuum reading is outside 5.9-9.8 in. Hg, check hose between intake manifold and vacuum gauge for clogging, kinking or leakage. If hose is okay, replace CVC valve and retest. Unplug EGR solenoid valve lower hose.
- Measure vacuum at idle. If vacuum is below 1.2 in. Hg, EGR control solenoid valve is okay. If vacuum is more than 1.2 in. Hg, check air flow hose to EGR control solenoid valve for blockage. If hose is okay, replace EGR control solenoid valve and retest.
- Disconnect No. 21 vacuum hose from between throttle body and intake air pressure sensor. Plug vacuum fitting at throttle body. Connect vacuum pump to No. 21 vacuum hose and apply 11.8 in. Hg vacuum. Raise engine speed to 2400 RPM. Feel operation of EGR control solenoid valve with your fingers.
- If EGR control solenoid valve is operating, system is okay. If EGR solenoid valve is not operating, check harnesses between EGR control solenoid valve and ECU (Blue/Red and Black/Yellow wires) for open or short circuits. If harness is okay, check EGR control solenoid valve.
- If EGR control solenoid valve is working, check EGR valve and lift sensor. To check EGR control solenoid valve, disconnect wiring harness from No. 2 control box. Disconnect No. 10 vacuum hose from vacuum hose manifold.
- Ensure there is air flow through hose. If there is no air flow, replace EGR control solenoid valve and retest. Connect positive lead of 12 volt battery to Black/Yellow terminal of No. 2 control box coupler. Connect negative lead to Blue/Red terminal.
- Pump air into No. 10 hose, making sure there is no air flow. If air is flowing through hose, replace EGR control solenoid valve and retest. See Fig 1 .
- To test EGR valve, start engine and let it idle. Disconnect EGR valve upper hose. Connect vacuum pump to EGR valve. Apply 5.9 in. Hg vacuum. If vacuum remains steady and engine dies, EGR valve is working properly. If vacuum does not remain steady and engine does not die, replace EGR valve and retest.
- If vacuum remains steady but engine does not die, remove EGR valve. Check EGR valve and manifold for blockage. Clean or replace as necessary and retest.
- To test EGR valve lift sensor, connect system checker harness between ECU and wiring harness connector. Turn ignition on. Measure voltage between terminal C13 of system checker harness (Red/Blue wire) and terminal C12 (Green/White wire).
- Voltage should be 1.0-1.4 volts. If voltage reading is 1.0-1.4 volts, substitute a known-good ECU. Retest EGR system. If EGR still does not operate properly, replace EGR valve lift sensor. If voltage reading is not 1.0-1.4 volts, turn ignition off.
- Check for open or short circuit in Red/Blue and Green/White wires between EGR valve lift sensor and ECU. Repair or replace harness as necessary. If harness checks okay, turn ignition on. Connect vacuum pump to upper hose of EGR valve.
- Apply vacuum to valve and measure voltage between terminal C8 (Red/Blue wire) of system checker harness and terminal C12 (Green/White wire). Voltage reading should be 1.2-3.8 volts. If voltage reading is not within specifications, replace faulty EGR valve lift sensor.
- If voltage reading is within specifications, substitute a known good ECU. Retest EGR system. If EGR system still does not operate properly, replace EGR valve lift sensor.