Hello everyone, well i joined up here cause im at a loss, ive trouble shot about everything i can think of and i cant get results. So heres the problem.... i have a 2000 tahoe LS with the 5.3L and its got push button 4wd. Well its snowing and pretty icy up here in tacoma washington and today my front end wont engage in auto 4wd and 4hi and wont even click down to 4 low. Ive gotten a service 4wd light on the message center. Now i reserched and changed the transfer case switch on the dash.... no joy, changed the 4wd actuator and still. No love, ran it through a code reader and it came back with actuator timed out error. (Now that error was before i changed the actuator). With the new actuator i hear it moving through but it wont go into 4wd at all. Right now i disconnected the battery in a effort to trick the computer but its a last ditch.... anyone got anything else i can try before i try to get a new T-case? Oh and when the 4wd went down i wasent getting any grinding or anything and it still moves under its own power in 2wd/4wd auto (but 4wd is not engaged)
Service 4wd and no 4wd
- Thread starter Merlin
- Start date
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LionsGuy
TYF Newbie
- Joined
- Feb 9, 2019
- Posts
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There is a ground wire, I believe under the truck on the drivers side frame. Check there and clean the connection, see if that is it. I have heard of this being a main culprit.
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@Merlin, the ground wire that @LionsGuy mentioned is on the frame under the driver's side. Easy to get to, less than a foot behind the LF tire. There are two ground bolts there and one of the (smaller?) ground wires is for the 4wd, I believe it's for the front diff actuator. Pull those bolts and clean the grounds; I recently did mine and one bolt hole was stripped so I put a nut on it.
When you say you changed the "actuator", are you talking about the front diff actuator, or the encoder motor on the transfer case?
What was the actual code that was read?
Take a look at this video, there are some procedures (except for grabbing the driveshaft!) for testing.
I would suspect the front diff actuator or a voltage problem at that connector, and would troubleshoot that before calling the TC bad.
EDIT: this video shows how to bench test the front diff actuator. I did mine on the truck using the 4hi switch, and also with the Tech2 scan tool. It's important to do it on the truck, since supply voltages can be different or affected by poor connections.
When you say you changed the "actuator", are you talking about the front diff actuator, or the encoder motor on the transfer case?
What was the actual code that was read?
Take a look at this video, there are some procedures (except for grabbing the driveshaft!) for testing.
I would suspect the front diff actuator or a voltage problem at that connector, and would troubleshoot that before calling the TC bad.
EDIT: this video shows how to bench test the front diff actuator. I did mine on the truck using the 4hi switch, and also with the Tech2 scan tool. It's important to do it on the truck, since supply voltages can be different or affected by poor connections.
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One other basic thing to check is the fluid level and condition in the TC and both differentials.
swathdiver
Full Access Member
Don't you GMT800 guys need to do a relearn with the Tech-2 when the encoder motors are changed?
Sorry the front diff actuator i did replace alone with the 4 button pannel inside the cab, i did see that video a bit eariler and the encoder was my next rundown to replace.... this tahoe is old and tired at over 201k miles. Ill try running down the ground wire and hopefully that will fix it. Thanks guys for helping me run this down.
Oh additionally i hear i believe the front diff actuator moving when i push the 4wd selector and the light is not on anymore but will come on if i try to select 4hi or 4low... just blinks at me and either banks out and the service 4wd light comes on or it flashes and goes back into 2hi or auto 4wd (to which the front end is definitely not engaging).
Oh additionally i hear i believe the front diff actuator moving when i push the 4wd selector and the light is not on anymore but will come on if i try to select 4hi or 4low... just blinks at me and either banks out and the service 4wd light comes on or it flashes and goes back into 2hi or auto 4wd (to which the front end is definitely not engaging).
Those are symptoms of a worn out encoder motor. Once you get to the point of ruling out other things, that's the next thing to change. Not exactly inexpensive but they're under $200 and can be had for less; they can also be rebuilt. Cheaper than a transfer case, and worth a try once you get to that point.
Without a Tech2 you'd have to be measuring switch and encoder voltages manually; the Tech2 lets you see that all in action. From what I've seen there is an 8v or 5v reference from the transfer case control module to the switch and to the encoder motor -- voltage depends on your year -- and you can see what each encoder position is returning for voltage (which tells the switch which lights to light and what position the drive is in).
And to answer the question that @swathdiver posed, no relearn is required for the encoder motor replacement. Plug n play on these.
Without a Tech2 you'd have to be measuring switch and encoder voltages manually; the Tech2 lets you see that all in action. From what I've seen there is an 8v or 5v reference from the transfer case control module to the switch and to the encoder motor -- voltage depends on your year -- and you can see what each encoder position is returning for voltage (which tells the switch which lights to light and what position the drive is in).
And to answer the question that @swathdiver posed, no relearn is required for the encoder motor replacement. Plug n play on these.
@Merlin - A couple more articles that you might find helpful:
http://www.atraonline.com/gears/2006/2006-08/2006_08_08.pdf
https://www.motor.com/magazine-summary/transfer-case-studies-diagnosing-gms-4wd-system/
The second one is probably most similar to your system. Mine is a few years newer and runs a different TCCM and encoder motor but theory of operation is the same.
http://www.atraonline.com/gears/2006/2006-08/2006_08_08.pdf
https://www.motor.com/magazine-summary/transfer-case-studies-diagnosing-gms-4wd-system/
The second one is probably most similar to your system. Mine is a few years newer and runs a different TCCM and encoder motor but theory of operation is the same.
Pull the front diff actuator and let it hang, then select 4hi on your dash switch. The actuator should fully engage in about a second or two. It would be valuable to check voltages there on the connector to be sure the full 12v is present (one of the previous videos on bench testing would show the correct contacts to check).
If the ground is determined to be weak at the diff actuator connector, the ground wire may also have a connector underneath or near the brake master cylinder in the engine compartment.
If the ground is determined to be weak at the diff actuator connector, the ground wire may also have a connector underneath or near the brake master cylinder in the engine compartment.
I had a similar problem that only appeared after driving thru water or in freezing weather. Replacing the encoder ring cured the problem. It’s an easy and inexpensive fix. The encoder ring is located near the rear of the front driveshaft on the transfer case, almost under the driver’s seat. I also sealed all openings around the encoder
ring with RTV to keep out moisture, which appeared to have caused my problem.
I have a thread that discusses the problems I was having before replacing the part.
