Won't go into 4 wheel drive

[wake_rider]

Thread revival warning.

I'm getting a blinking 4wd light at all times (2000 limited with push button and J-shift).

The problem started 4 days ago and it happened for just a minute then went off. I didn't feel 4wd engage but my butt gauge isn't the best at resisting influence from an overanalyzing mind. It did this on and off over the weekend and eventually just has gone to where it constantly blinks and I'm getting no 4wd engage.

So tonight I've tested the vacuum on the VSV's and the vacuum isn't ever changing sides regardless of what I'm doing with the transfer case. So I switched the lines to pull vacuum for the opposite side hoping to engage 4wd and rule out the front diff but I still had no change. So now I'm completely stuck in my troubleshooting.

I've also pulled and checked continuity on the front diff locker sensor as well as the two on the back of the transfer case actuator... all three are getting continuity when the plunger is pressed in. I'm also not hearing any change when I press the AWD button or when I shift into 4-hi or 4-lo (well, not outside of the actual shifter linkage making noise as I move it around).

Any idea where I should be going next?

Forgot to mention that it's also blinking when the truck is not running and the key is in the "on" position. I don't know if that helps at all but I thought it might be of use to wiser minds than mine.

 

[TheDurk]

Thread revival warning.

I'm getting a blinking 4wd light at all times (2000 limited with push button and J-shift).

The problem started 4 days ago and it happened for just a minute then went off. I didn't feel 4wd engage but my butt gauge isn't the best at resisting influence from an overanalyzing mind. It did this on and off over the weekend and eventually just has gone to where it constantly blinks and I'm getting no 4wd engage.

So tonight I've tested the vacuum on the VSV's and the vacuum isn't ever changing sides regardless of what I'm doing with the transfer case. So I switched the lines to pull vacuum for the opposite side hoping to engage 4wd and rule out the front diff but I still had no change. So now I'm completely stuck in my troubleshooting.

I've also pulled and checked continuity on the front diff locker sensor as well as the two on the back of the transfer case actuator... all three are getting continuity when the plunger is pressed in. I'm also not hearing any change when I press the AWD button or when I shift into 4-hi or 4-lo (well, not outside of the actual shifter linkage making noise as I move it around).

Any idea where I should be going next?

Sounds like the actuator on the front diff is toast, or at least needs servicing. Could be the connecting hoses, too.

 

[FILTHEE]

Thread revival warning.

I'm getting a blinking 4wd light at all times (2000 limited with push button and J-shift).

The problem started 4 days ago and it happened for just a minute then went off. I didn't feel 4wd engage but my butt gauge isn't the best at resisting influence from an overanalyzing mind. It did this on and off over the weekend and eventually just has gone to where it constantly blinks and I'm getting no 4wd engage.

So tonight I've tested the vacuum on the VSV's and the vacuum isn't ever changing sides regardless of what I'm doing with the transfer case. So I switched the lines to pull vacuum for the opposite side hoping to engage 4wd and rule out the front diff but I still had no change. So now I'm completely stuck in my troubleshooting.

I've also pulled and checked continuity on the front diff locker sensor as well as the two on the back of the transfer case actuator... all three are getting continuity when the plunger is pressed in. I'm also not hearing any change when I press the AWD button or when I shift into 4-hi or 4-lo (well, not outside of the actual shifter linkage making noise as I move it around).

Any idea where I should be going next?

There are an additional 3 switches near the top of the transfer case that should be checked for continuity as well. They are a pain to get to and found it easier to remove the center console and get to them from up there.

 

[wake_rider]

Sounds like the actuator on the front diff is toast, or at least needs servicing. Could be the connecting hoses, too.

I picked up a vacuum tester at Harbor Freight just a bit ago. I'm going to test my lines and try pulling an alternating vacuum on both sides of the actuator and see of I get any change. As of now, I feel like the front actuator is locked because my driveshaft is always spinning if the front wheels are moving, but it's not getting any power from the transfer case.

There are an additional 2 switches near the top of the transfer case, one each side that should be checked for continuity as well. They are a pain to get to and found it easier to remove the center console and get to them from up there.

Awesome. I'll look into it after getting my kids down tonight. Is it obvious once you pull the center console how to get to them?

 

[TheDurk]

I picked up a vacuum tester at Harbor Freight just a bit ago. I'm going to test my lines and try pulling an alternating vacuum on both sides of the actuator and see of I get any change. As of now, I feel like the front actuator is locked because my driveshaft is always spinning if the front wheels are moving, but it's not getting any power from the transfer case.

You didn't tell me that. I posted how to troubleshoot your ADD. Now you tell me there is nothing wrong with your ADD.

Do you also get no power out of the TC when using the j-shift, or just with the button?

 

[wake_rider]

You didn't tell me that. I posted how to troubleshoot your ADD. Now you tell me there is nothing wrong with your ADD.

Do you also get no power out of the TC when using the j-shift, or just with the button?

I'm not ever getting power out of the TC to the front diff. That said, no matter if I'm using the AWD switch or the J-shifter, on or off, the front end is staying locked it seems. Also, when using the button or shifter I've always heard some clicking in the front diff but now I'm not hearing anything.

 

[wake_rider]

So here's where I am. I tested the front actuator by using a vacuum gun and I was able to get the front to unlock, so now I'm completely in 2wd (though my lights are still flashing). This at least makes me feel safe about driving the truck.

I'm only getting the blue vacuum line (to engage 4wd) to work, and I'm never getting the vacuum to switch to the "unlock" red/brown VCV. Is there something I can check as to why I'm not getting the signal to switch between the two? Would the sensors being out on top of the TC have any influence on the system not sending the signal to the VCV's to switch?

To keep it unlocked at the front diff, I just switched the hoses at the VCV's so I'm using the functioning side to pull a vacuum at the diff actuator to keep it unlocked.

 

[FILTHEE]

Awesome. I'll look into it after getting my kids down tonight. Is it obvious once you pull the center console how to get to them?

I just remembered (it's been a while) that there are 3 switches on the topside of the TC. 2 on the driver side and one on the passenger side. Once you get the gear selector and TC shifter out, you can look in the hole and kind of see the switches toward the rear of the vehicle.

I ended up using a box end wrench after trying to use a crows foot and a O2 sensor socket which didn't work for me because of clearance.

 

[FILTHEE]

So here's where I am. I tested the front actuator by using a vacuum gun and I was able to get the front to unlock, so now I'm completely in 2wd (though my lights are still flashing). This at least makes me feel safe about driving the truck.

I'm only getting the blue vacuum line (to engage 4wd) to work, and I'm never getting the vacuum to switch to the "unlock" red/brown VCV. Is there something I can check as to why I'm not getting the signal to switch between the two? Would the sensors being out on top of the TC have any influence on the system not sending the signal to the VCV's to switch?

To keep it unlocked at the front diff, I just switched the hoses at the VCV's so I'm using the functioning side to pull a vacuum at the diff actuator to keep it unlocked.

I had the same issue with my VSV's and replaced them with a used one off eBay after testing them.