Service 4WD

[BozDMAX]

I don

[kingkong]

In July 2006 GMC 3500 with 110,000 miles on it started experiencing problems with 4 WD . First indicator lite--service 4WD drive lite came on. Changed dash switch with no improvement then unit would go into neutral and the only way to get it back into gear was to remove both fuses. This is what I have done so far--Changed position indicator switch --reprogrammed control modial--updated ECM and reupdated ECM. Still getting Code Co327 --Encoder circuit malfunction. Now have changed the encoder motor ($700) but after 30 minutes running --service 4WD drive--dash lite still comes on, cancel it and that ends the problem for that day. Do I have a bad connection? This has been going on for over 6 months with expensive service work involved. Of course it is out of warranty--l68,533 miles now.

[More Power]

Check the grounds... The trans/transfer case harness has a ground connection that breaks out of the harness just ahead of where it leaves the frame and jumps to the trans & transfer case. Check that ground connection.

Also, the engine/trans have their own grounds as well. I hope you kept the original encorder.... :)

Jim

[kingkong]

we already removed the grounds and cleaned them , GM recomnended change the wires will do that tomorrow. thanks kingkong

[kingkong]

replaced wires from encoder motor to control moduol under the dash [ 3 ] drove the truck 360 miles today no warning lite. [time will tell] been messing with this problem for 7 months . kingkong

[Onebigcanuck]

I had the same problem with mine. They replaced the sensor under warranty, I've had no problems since then.