Axle disconnect actuator trouble shooting

[BrianF]

Alright, I had posted my follies on my 4x4 and random dash light issues on another thread but I need to break my issues down a bit further.

2006 trailblazer 4.2, reg wheelbase, 250,000km.

Recently started lighting up like a Christmas tree. Abs and e brake lights came on periodically and now on full time.

As it was suggested, I will be replacing the ignition switch, which should be shipped soon. I pulled the switch out and cleaned some corroded contacts. No change in the abs and e brake light but on start up, the service 4x4 light is on.

Cleaned the under hood and chassis ground under the driver feet. No change in any of the lights.

The 4x4 switch appears to work (I do the suggested workout once in a while). The 2x4 light is illuminated and when I select 4 hi or low, you can hear the TC shift but the indicator light just flashes on the attempted setting. I verified its shifting as the case will go into 4 low.

I intend to pull the disconnect and actuator tomorrow as planned preventative maintenance. If nothing jumps out as corrosion or mechanically stuck, what tests can I conduct without multi meter?

I am hoping to test for a reference signal or voltage change on startup or trying the switch. Hoping to rule out a wiring issue ... thanks for looking.

 

[Mooseman]

Well, just pulling the actuator and seeing if it moves with the switch is the easiest. If the disco is mechanically stuck, it could be what's throwing the light. If it clears up the light when it's out, then the disco is next to take apart and inspect. Hopefully it's just the congealed grease that's preventing it from moving.

 

[BrianF]

Thanks, ya that's the plan. It has 90,000km since I rebuilt the disconnect and planned to pull it all apart and degrease. I sure hope it's a simple fix. Should be tackling this today...

 

[BrianF]

Alright, so I removed the disconnect and actuator. Now first, the disconnect. I had used a little bit of grease where it fits into the oil pan, this proved useful this go around. I gave it some taps underneath to force some rotation. Back and forth and then I popped it off straight on with one had. I just popped it right out. I own that bitch now!

I had the actuator hanging there and switched it into various 4x4 ranges. The worm gear never moved. No sounds either. The service 4x4 was still there on start up. I checked under hood and rear fuse block but all was well.

So, on start up perhaps there is a reference signal that is not being sent or being received. I will check this with my multimeter after lunch. The service 4x4 light came on right after start up after I was pissing around with the ignition switch. It was in 2 wheel drive and I did not use the switch at all.

The next quest is to test the actuator. Wondering what order the 4 pins are and if I can run a jumper from the battery to apply 12 volts directly and check the motor.

 

[BrianF]

Alright I did some basic tests. I have reisitance between two combinations of pins on the actuator. What does that mean? Who the hell knows. I tried to test the connector pins but my probe is way to big and I cannot risk wrecking it. Oh well.

I cleaned up the disconnect cleaned up some other parts and regresased the caliper slide pins. It's all buttoned back up as I need to run it for a bit.

Once I get the new ignition switch in, I will recheck some connectors under the dash. If no change, I will order up those programs and blue tooth obd2 module to check that chassis code.

 

[Mooseman]

Unless the wiring has been damaged, I'd be willing to bet that the actuator is done. Looking at the schematics, looks like + and - are constant and the actuator is actuated by a signal on two wires from the TCCM. No idea what that signal is. You could check continuity between the two wires that go to the TCCM and the other two have power.

 

[BrianF]

Moose, thanks! I should have decent enough access to the actuator connector with the front end up on blocks. I will see about making some real fine wires to prove the connector. I will check for continuity and see what signal the tccm sends down the pipe. There's four wires, not an infinite amount of options.

 

[BrianF]

Now I need to link up the post here on GMTnation. Similar problem discussed. possible TCCM issues. I had checked the underhood #8 fuse and the #48 fuse in the underseat block, all good.
The ground mentioned on Moose's diagram is G107 and if this is in fact the correct ground mentioned in the other post, it should be on the "left side of the block" so I will have another look for that specific one. After looking at some schematics supplied by Moose, the ground G107 is in fact on the left side of the block (driver side) near the starter.
Now a further problem.... the blend doors are not working. Fan blows but it is limited to the windshield and feet. Great.

 

[BrianF]

Ahhggghhh its just cascading electrical problems but I will see what I can figure out. Seems the blend doors is a common problem when disconnecting the battery for some period of time. I had that thing hooked and unhooked more than a hooker if a hooker could hook.

Appears the first course of action is a reset by removing fuse 36 and 39, which should be the rear block. Unhook for a few minutes, then turn the ignition on, no run for a few minutes then run. The doors should do there relearn.

Edit: tried relearn, no dice, in fact it was the fan that quit. All fuses fine, will have to check the blower resistor...

 

[Mooseman]

Hopefully the blend door actuator didn't self destruct. Pulling the HVAC-B fuse for a minute, replacing it and turning the key to RUN while it relearns should do it unless it's borked, which would have happened eventually if it is. The induced relearn with the battery disconnect just precipitated it.(hopefully not)

 

[BrianF]

That is the plan, thanks for the feedback.

I was reading one of Roadie's posts about the actuator on the old site. Very informative. The TCCM signals the motor to work. If there is too much resistance or something jammed, the TCCM quits trying and you have to disconnect power to it by a reset or turning the vehicle off.

He pulled one actuator apart and found some of the connections were coated in grease, causing resistance which caused the TCCM to give up trying.

I think I may pull the actuator off again and pull it apart, hell if I have to JB weld it back together, so be it.

 

[BrianF]

I did the relearn on the HVAC but no change. I didnt hear the blend doors moving with the mode switch but wait! There is zero fan speed! On any of the 5 settings. Well shit. I checked all fuses again. All good.

Ground g107 inspected. Was in good shape but cleaned anyways. No change.

Pulled the fan resister, it looks good, and several of the leads all have varying levels of resistance. Tested the red 12v on the flat connector. A cool 12v. Key on fan at 5 and the orange wire now has power. Thanks to May03lt's video for that.

Pulledbth fan. There is slight resistance and continuity between the positive and negative leads. I will do a 12v jump wire to check if the fan runs sometime tomorrow.

Now I know this post is supposed to be about my disconnect actuator but something started this mess and drug all these other systems along. I may wait for further diagnosis until the new switch is installed.

 

[BrianF]

Most of my situation has been resolved. New switch came in today. 4wd works. Can clearly hear the disconnect working and you can feel the vehicle crow hop on tight turns. The blower fan also is back working.

Now.... my abs and e brake light are still on. I guess I will see about that program to check chassis codes and recheck some grounds.