Tired of 4WD problems

[se1911]

Current issue. Service 4wd light is on and nothing happens when changing switch from 2hi to other modes. All switch lights come on with key, then go out except 2hi. AWD/4hi/4lo lights don't come on when rotating selector to that mode.

Quick troubleshooting - listened for both motors to actuate with engine off. Both encoder motor and 4wd actuator are quiet.

Checked fuze 8 and 48. Pulled 8 to try to reset TCCM.

Parts replaced in last 6 months.

TCCM, encoder motor, 4wd actuator and switch. 157K 02 TB, all fluids changed regularly.

 

[The_Roadie]

Assuming you replaced the 2002 TCCM with something newer, I'd be looking at the wiring harness and especially the connection from the switch to the TCCM. Do you have the schematics and have you checked signals at the TCCM connector? The lamp test is a pretty good indicator that the TCCM is getting power.

When you rotate the switch to another position, does the 2WD light stay on and not even blink?

 

[se1911]

Assuming you replaced the 2002 TCCM with something newer, I'd be looking at the wiring harness and especially the connection from the switch to the TCCM. Do you have the schematics and have you checked signals at the TCCM connector? The lamp test is a pretty good indicator that the TCCM is getting power.

When you rotate the switch to another position, does the 2WD light stay on and not even blink?

I do have schematics, but haven't had a chance to test anything yet. TCCM was the new part #.

The 2wd light does stay on and not blink when changing positions.

 

[The_Roadie]

Sure sounds like the TCCM isn't seeing the switch change position. Did you EVER see the system operate nicely? Could be an internally bad replacement switch also.

 

[se1911]

Sure sounds like the TCCM isn't seeing the switch change position. Did you EVER see the system operate nicely? Could be an internally bad replacement switch also.

After replacing the encoder motor last month everything was working good. The switch is the part that hasn't been replaced. When I was troubleshooting last month, I checked the voltage drops leaving the switch and all WAS good.

I'll check it later when I get a chance. Hopefully its the switch and not a wiring problem.

Thanks

 

[The_Roadie]

But, but, but...your first post said the switch HAD been replaced.

 

[se1911]

But, but, but...your first post said the switch HAD been replaced.

Sorry, wasn't clear. The actuator switch on the disconnect was replaced. Front, passenger side.


The selector switch on the dash hasn't been replaced.

 

[The_Roadie]

Ahhhh, we just call that the front axle actuator, but there *is* a copper finger gadget that slides on a PCB inside that reports back the position it attains, so that could be called a switch. The way it actually works is with a tremendous step-down planetary gear train extending and retracting a plastic button, as you saw when you swapped it. Boy you've paid your dues on this system, eh?

 

[se1911]

So it's not the selector switch.

Now selector switch light will stay in auto regardless of the switch position. After reinstalling fuze 8, the light will flash at switch location, but will stay on at auto.

If I remove/install fuze 8, I can hear the actuator (passenger front) engage/disengage. So for some reason, it wants to keep the actuator in the auto position.

Still no sounds from encoder motor.

 

[se1911]

If I have the drivers door open, and put the key to "On" I can hear the actuator engage or disengage. The pitch get higher.

Then turning the key to "Run" the actuator reverses. Pitch gets lower.

Then selector light goes to "Auto" and service 4WD light comes on.

If the door is closed, none of this happens except the auto and service light.


Will a normal scan tool I can borrow from O'Reilly's Auto read 4WD codes, or do I need a specific type of scanner?

 

[djthumper]

Will a normal scan tool I can borrow from O'Reilly's Auto read 4WD codes, or do I need a specific type of scanner?

IIRC you need a Tech II to get the information.

 

[The_Roadie]

Crappy TCCM or confusing messages on the shared data communication bus. What's the TCCM's pedigree? Got another one to swap in from a buddy?

 

[se1911]

Swapped TCCM and both do the exact thing. Both new part #

Just used scanner from O'Reilly's "Innova 3120 Lat" didn't show any codes.

Very confused about the open vs closed door.

Is it possible encoder motor died after a month?

 

[se1911]

Pulled the encoder motor, left it connected to the harness. Pulled fuze 8.

After installing fuze 8, I can hear slight hum (very quiet) from encoder motor. As if it is trying to turn, but its not moving.

Any way to further test these? Should be covered under Dorman warranty since it was replaced in July.

Do you think this is the problem, or could it be something else? This whole thing is screwy.

 

[The_Roadie]

It is totally screwy, and I'm out of ideas except that the encoder motor is either being told to do something strange, or it's not obeying a valid command. Personally, I'd pull it and bench test it while checking the sensor for smooth resistance changes.

 

[se1911]

It is totally screwy, and I'm out of ideas except that the encoder motor is either being told to do something strange, or it's not obeying a valid command. Personally, I'd pull it and bench test it while checking the sensor for smooth resistance changes.

Have no idea how to bench check the encoder motor.

Read another thread and you talked about trying to rotate by hand the spline on the transfer case the encoder motor rotates. Can this be done by hand (finger and thumb) or with a ratchet and socket. Not sure how much force is needed to rotate it, but I couldn't turn it with finger and thumb.

 

[The_Roadie]

I've never done it, but I think you have to grab it with vise-grips. Not a horrible amount of torque, but more than fingers.

You can also see if the encoder motor moves nicely when it's disconnected from the transfer case and just in midair.

 

[BRomanJr]

Pulled the encoder motor, left it connected to the harness. Pulled fuze 8.

After installing fuze 8, I can hear slight hum (very quiet) from encoder motor. As if it is trying to turn, but its not moving.

Any way to further test these? Should be covered under Dorman warranty since it was replaced in July.

Do you think this is the problem, or could it be something else? This whole thing is screwy.

The Encoder Motor will behave exactly like that IF it is not commanding torque to the Front and is in A4WD mode, In that mode the Encoder brake is being energized (brake released) causing a slight hum.
If your dash switch does not make it change (motor turns the encoder shaft) then you have to diagnose with a Tech II.

You need to know if the dash switch is commanding a mode change to the TCCM and then is the TCCM commanding an Encoder move.

TCCM codes will be very helpful, the TCCM is smart enough to throw a code for most problems.
The 4WD Service light means you have codes.

 

[se1911]

The Encoder Motor will behave exactly like that IF it is not commanding torque to the Front and is in A4WD mode, In that mode the Encoder brake is being energized (brake released) causing a slight hum.
If your dash switch does not make it change (motor turns the encoder shaft) then you have to diagnose with a Tech II.

You need to know if the dash switch is commanding a mode change to the TCCM and then is the TCCM commanding an Encoder move.

TCCM codes will be very helpful, the TCCM is smart enough to throw a code for most problems.
The 4WD Service light means you have codes.

That's good info, thanks. Since my encoder motor is still under warranty, I've got a new one on the way. This one didn't rotate after I pulled it off the transfer case and cycled the selector switch on the dash. I know the TCCM and selector switch are good.

Unless there is a wiring issue. Didn't want to drop $100 for a scan. Don't have access to a Tech II. Will see what happens after I swap parts.

 

[se1911]

Got a replacement encoder motor from Rockauto and swapped it out. All is working again now. Hard to believe the old one died after a month of not being used.

Hopefully nothing else is wrong that caused it.

 

[Mooseman]

Just for reference, what brand was the dud encoder? What was the replacement?

 

[se1911]

Just for reference, what brand was the dud encoder? What was the replacement?

Dorman P/N RB 600-903 from Rockauto. Same replacement

They have been very easy to deal with on the return/replacement part.

 

[The_Roadie]

I've heard some good, some bad, things about various Dorman replacement parts. Their window regulators and front axle actuators have been fine, IIRC. Transfer case encoder motors and fan clutches, not so much. Rockauto as a distributor seems to be top notch about replacing duds.

As long as they're not like Fry's Electronics, which has a policy of putting customer returns back on the shelf until they've been returned three times (again, IIRC - I heard this from somebody who used to work at Intel in CPU support) , on the assumption that most of their customers are idiots.