First pick up a new gasket at the GM dealership, part # 125672275 or Fel-Pro # 70783. Cost about $3. Or $4. at dealership, Auto Zone wants $12 for one!
The E.G.R. valve has 5 wires going in
1 = Gray
2 = Black Ground
3 = Brown
4 = Gray has 5 volts in run
5 = Pink has 12 volts in run
Remove the 5-wire plug, turn ignition switch to run, and probe socket # 5 for 11.5 to 12 volts and socket # 4 for 5 volts. Turn ignition switch to off set VOM to ohms and probe socket # 2 and make sure it has a good ground, less than 1 ohm.
With VOM still set to ohms probe egr. pin # 1 to pin # 5 , should read 9 to 11 ohms. Pin # 1 and # 5 go to the coil that pulls open the pintle valve when the PCM gives pin # 1 ground.
Pin’* # 2, #3, and # 4 go to internal potentiometer that tells the PCM if the pintle is open or closed.
Probe pin # 2 to pin # 3 should read around 800 ohms.
Probe pin # 3 to pin # 4 should read around 3500 ohms.
Probe pin # 2 to pin # 4 should read 3600 ohms.
The pintle valve is spring loaded and should be air tight when seated. If the valve is not closing use something like dental tools to remove any carbon build up on the pintle face and shaft. The carbon does not come off easily but is worth the time to remove as a new E.G.R. is pricey.