My buddy has a 2009 Alpha Adventure with about 100k miles. He tells me that sometimes it will shift from 4 H to 4 H lock on it’s own and the 4 H lock button lights up. He tells me that it might go a month or more without it happening……when it does he said all he has to do is shift the tranny to neutral and press the 4 H button and he is good to go until the next time. He is not mechanically savvy and takes everything to the dealer.
I told him my guess is a faulty transfer case control module. Any one experienced something like that or have comment/ideas?

 

Any Codes Active/History? Did you try tap test the switch? Any liquid air fresheners above the switch?

PIP4161
Subject: Service 4WD Light On and The System Inoperative, Switch Contamination Models: 2006-2008 Hummer H3
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:

Some customers may comment about a Service 4WD Light on and transfer case or rear differential lock system inoperative. Technicians may find various switch DTCs or open fuses and the transfer case select switch contaminated

Recommendation/Instructions:

A number of 4WD switches have been received through the Warranty Parts Center that show obvious signs of contamination caused by liquids being spilled through the HVAC vents. On an H3 vehicle these liquids will run in behind the IP face plate and leak into the 4WD switch, the radio and if severe enough may also cause various fuses to become open.

In particular, liquid air fresheners that clip onto the HVAC vents can spill onto the IP components. Air fresheners will chemically blister the paint on the 4WD switch and cause the buttons to stick. A B2725 or B0790 switch DTC may be set. The switch may also smell like perfume. Additional paint blistering may occur on the radio.

The affected components will have to be replaced. However, contamination of this nature does not constitute a defect in materials or workmanship for which General Motors would be responsible. Each suspect vehicle should be carefully inspected and a decision made at the local level regarding GM participation with the repair expenses.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

DTC B2745

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

TCS Switch Signal Circuit

B2745 Traction control cannot be manually disabled.

Circuit/System Description

The driver may disable the Traction Control System (TCS) by pressing the traction control switch. The body control module (BCM) supplies a 12-volt signal on the traction control signal circuit. When the traction control switch is pressed, this voltage signal is grounded.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

The BCM detects low voltage on the traction control signal circuit for 60 seconds.

Action Taken When the DTC Sets

• The BCM sends a serial data message to the electronic brake control module (EBCM) informing the EBCM that the desired TCS state cannot be determined.
• The EBCM defaults the TCS status to enabled.

Conditions for Clearing the DTC

The DTC clears automatically from Current status when the fault is corrected. Use a scan tool to clear the DTC from history status.

Diagnostic Aids

An intermittent short to ground on the traction control signal circuit is the most likely cause of a history DTC when no problem is found. When the Conditions for Setting this DTC are present, the driver is not able to disable traction control.

Circuit/System Testing

⇒X If DTC B2745 does not reset, go to Diagnostic Aids.

1. Turn OFF the ignition for 5 seconds, then turn ON the ignition and wait at least 60 seconds.
2. Turn the ignition OFF. Disconnect the traction control switch harness connector. Turn the ignition ON and wait at least 60 seconds.
3. If DTC B2745 does not reset, replace the traction control switch.
4. If the DTC B2745 resets, check the TCS switch signal circuit for a short to ground or replace the BCM.

 

Thanks,
He works off shore oil rigs and his H3 is at the port of Corpus Christy right now. When he comes home we will engage the Tech II. So far he hasn’t mentioned any DIC messages. Great dude and hope to help him. Next time I talk to him, I’ll encourage him to sign up for the forum (again….)!

 

Hmmm. Bad (or dirty) console switch?