Running Tests

1. Connect vacuum tester with Y distributor onto EGR valve. Operate vehicle on a dynamometer (or equivalent) in 5th gear or "D" at partial load, and check vacuum reading.
a. With a vehicle speed greater than 56 ± 5 mph, 0 inches of vacuum should be obtained.
b. With a vehicle speed less than 56 ± 5 mph, 700 mbar (20 in. Hg) of vacuum should be obtained.
c. If not, test switchover valve.

2. Check electrical activation of switch-over valve.
a. Connect multimeter onto switch-over valve electrical connector and operate vehicle on a dynamometer or equivalent.
b. If voltage is obtained (approximately 12 volts) at a vehicle speed of less than 56 mph, check wiring or replace defective components.
c. If no voltage is indicated, replace switch-over valve.

3. To test the Hall effect speed sensor:
a. Disconnect the EGR control unit.
b. Measure the voltage between sockets 9 (+) and 1 (-) on the EGR control unit plug with the preglow/starter switch turned to position '2'.
c. Move the vehicle at least 1 m (3 ft).
d. Voltage should cycle between 0 and 12 vdc.
e. Repair wiring if necessary.
f. If the wiring is OK, replace the Hall effect sensor.