Service 4x4 message on

2007 CHEVROLET SILVERADO

150,000 MILES • 5.3L • V8 • 4WD • AUTOMATIC

FREDERICK A. ROSE

MEMBER
3 POSTS
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I have the truck listed above with the NQH Magna Power-train transfer case. The "Service 4x4" notice has come on and I would like to test the transfer case shift motor to see if it is bad. Do you have the electrical schematic of the electrical connector on the transfer case shift motor?

The transfer case motor is the same as a Dorman 600-899.

I did find a set pf schematics here:
https://www.gmupfitter.com/files/media/photo/87/2007_LD_ElectricalPickupsChassisCabs.pdf

I would like to find a set of trouble shooting guides that will help me detect what is wrong, like bad grounds or broken wires. Simply knowing what conditions need to be set; like the key on and the switch in 2H. I should see such and such voltages on what pins. My scanner does not show any codes, but it is a Launch CRP123 CReader professional and may not show all the codes.

The switch schematic on page D-9 does not make any sense to me. The way it is wired will always give 5 volts no matter what position the switch is place in. The ground or signal line must be drawn in the wrong place. I think it is supposed to be a simple voltage divider.

Thank you for any help you can provide,
Fred

Mar 11, 2020 at 8:10 AM

94 TRANSAM

CERTIFIED EXPERT
680 POSTS

Are there any malfunctions other than the service 4x4 message? Be specific if there are other issues please so I can get you the best info. Can you run the codes?

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Rich

Mar 11, 2020 at 8:47 PM

FREDERICK A. ROSE

MEMBER
3 POSTS

I had left the switch in "Auto" and the last time I switched it was a few months ago. At that time it worked properly. The truck seems to be in 2H and I cleaned up (removed and wire brushed) the ground connection to the frame under the drives side. If you can, take a look at the shift switch schematic and let me know what you think. A resistor voltage divider has to have the Vout tap in the center of the resistors, the voltage supply on one end of the two resistors and ground on the other end.

Mar 12, 2020 at 9:59 AM

STRAILER

CERTIFIED EXPERT
53,854 POSTS

Hello,

It sounds like the encoder has gone out. here is a guide to help you check the connection and instructions on how to replace the motor in the diagrams below:

https://www.2carpros.com/articles/how-to-check-wiring

Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.

Images (Click to enlarge)

Mar 12, 2020 at 12:35 PM

FREDERICK A. ROSE

MEMBER
3 POSTS

A little more digging and looking at the older posh button type switch ... I think the diagram is actually indicating the switch parallels the 9.09K Ohm resistor with which ever one you select and it A to D is determining the resulting resistance. The schematic shows another resistor connected to ground below the A /D PD point. the Triangle connected to the neutral position is only indicating a contact point (?) . So if I measure the resistance from pin 11 to 12 I should see 138, 663,1921,1516 or 2345 Ohms...Auto, 4H, neutral, 2H, 4L.

Mar 12, 2020 at 12:42 PM

94 TRANSAM