service 4wd light, many codes set - 2001 sub.

[mike_2001]

Hello.

 

I have a 2001 suburban with push button 4wd, with the "auto 4wd" control.

 

I have had the service 4wd light turn on periodically this summer. It comes and goes. It is not on currently. I have had problems switching into and out of 4wd when it was acting up. Some of the symptoms, from memory:

 

-light on 2wd switch not illuminating (usually after switching out of 4wd)

-reluctance to switch out of 4 H into 2H. I have found it helps to switch into Auto 4wd first.

 

Last weekend, I used 4H, and switched back into 2H without a problem.

 

As winter is approaching, I decided to pull the codes before blindly replacing the switch. To this end, I used my OBD2 interface and manual commands on wOBD2 program on my laptop. When I pulled "current codes", I don't believe there were any. When I pulled all codes, the list was surprisingly long. Seems like nearly all available codes for the TCCM. Here they are, translated from Hex:

 

C0376

C0300

C0305

C0309

C0308

C0315

C0310

C0550

C0327

C0387

C0374

C0362

C0367

C0323

C0324

B2725

U100 (I think I read this one right)

 

Can all of these be triggered by an intermittent switch malfunction? Any thoughts would be greatly appreciated.

[Jsdirt]

Can't help you with the codes there, but most 4x4 issues in that generation, and in some of the newer ones, are due to a faulty switch. There's a whole multi-page thread on that issue somewhere on the forum ...

 

Found this one, but it's not the one I'm thinking of ... http://www.gm-trucks.com/forums/topic/86584-service-4wd

[gmtech4]

start with clearing the codes and try again to shift ,rescan,that is the code to diagnose,,,dont guess as to whats wrong

[Badass69]

Probably the encoder motor on the t case. Or at least the circuit board in the encoder motor. I know a lot of guys say its the dash switch but I have yet to have those fail versus the encoder motor. Clear the codes however and see what reoccurs. It cab be either or unfortunately

 

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