COOLANT THERMO SWITCH
Place thermo switch in water. Raise water temperature. Connect an ohmmeter and check for continuity above 131°F (50°C). If not, replace coolant thermo switch.
ELECTRONIC EGR CONTROLLER
- Using a voltmeter, connect positive lead to the Light-Green or Light-Green/Black wire at the vacuum switching valve wiring connector. Connect negative test lead to Black/Yellow wire.
- Check for 12 volts to vacuum switching valve(s) when engine speed is less than 3000 RPM. If not, replace EGR controller.
EGR VALVE
- Detach vacuum hose from EGR valve and connect outside vacuum source, such as hand pump with gauge. Apply vacuum, EGR valve should not leak down.
- While applying vacuum, watch movement of valve stem. At 17.7 in. Hg, stem should move diaphragm to full up position. If valve does not respond as indicated, replace EGR valve.
THROTTLE POSITION SENSOR
Connect a voltmeter to the Blue/Yellow (positive) and Blue/Red (negative) color coded terminals without disconnecting the throttle position sensor. Open throttle lever to within 9/32" (7 mm) from idle stop screw. Voltmeter should read 3.3-4.4 volts after starting the engine. If not, replace throttle position sensor.
P'UP
Remove thermal vacuum valve from engine and place sensing portion in water, 115-129°F (46-54°C). Blow through hoses connected to valve. Air should pass through. If not, replace valve.
Attach a vacuum pump and gauge to port "S". Attach a vacuum gauge to port "Z". Apply 27.5 in. Hg to the vacuum regulator valve. Vacuum gauge on port "Z" should read 8.8 in. Hg. If not, replace vacuum regulator valve.
VACUUM SWITCHING VALVE(S)
The vacuum switching valve(s) may be checked by connecting 12 volts directly to terminals. With 12 volts connected, listen for plunger operation noise.