Epr Vacuum Circuit Check - GMC G Service Manual

6E2-20 DIESEL EMISSIONS
EPR VACUUM CIRCUIT CH ECK
VACUUM .
FROM
VACUUM PUMP
EPR SOLENOID
N.C.
10 2-86
-
Circuit Description:
The EPR solenoid controls vacuum to the EPR valve.
The EPR solenoid, when energized, allows vacuum pump
vacuum to close the EPR valve and increase exhaust back
pressure for proper EGR operation. The EPR valve is a
combination vacuum actuator and exhaust restrictor plate.
When vacuum is applied to the actuator, the resistor plate
closes to increase exhaust system back pressure to allow
the EGR valve to function more efficiently.
6.2L (LH6) DIESEL
EPR VACUUM
ACTUATOR
439 PNK/BLK
Test Description:
Numbers below refer to circled numbers on diagnostic
chart.
1. Checks for normal EPR vacuum at idle. Since electri­
cal circuit was verified as OK on prior chart, if no
vacuum is present, it is due to no source vacuum
(vacuum pump) or a restriction or leak in vacuum
lines to valve, including the solenoid.
2. EPR solenoid is de-energized, so no vacuum should
be present.
3. Checks for normal operation of EPR valve. When
vacuum is applied to vacuum, valve actuator should
move and hold.
538 DK GRN
FUSE
E C M
9-9-86
8S3959-6E