Yea another CDL diagnostic thread

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sgmartz

sgmartz

Joined
Dec 7, 2020
Threads
7
Messages
37
Location
Evergreen, CO
Hi all, I am following a few different troubleshooting guides to figure out my CDL issue.

Problem:
CDL on in 4H and 4L
No dash light in any t case position
Vehicle engages 4H/L gearing appropriately
It does have an upgraded 3:1 lo gear set from PO (not sure if this would cause anything)

Diagnostics:
Checked relay
Cleaned all plugs on t case

Next steps:
Check actuator side resistance and connect 9v battery to try to get it to operate
Check CDL dashlight

Figured I’d post because I didn’t find another CDL issue like mine. I wanted to verify if I am on the right track and if there is anything additional to check. My two theories are 1)actuator is dead 2)4L sensor is stuck and a CDL light is out.

Thanks
 
Two more things

I confirmed it’s locked by raising a front tire and trying to spin it in 4H

It’s a 97 so no CDL day switch
 
Switch on top fwd of Xfer case, if , like you said, it is engaging.
 
More on this. Also documenting for someone else to search.

Condition:
CDL is locked in 4H and 4L verified with tire test
No CDL on in dash
ABS light on
3:1 t case, it’s a new to me LC80 and the PO said that when he had the t case work done is when he noticed the light stopped working (several years ago)

Diagnostics:
Relay test - pass
Fuses - pass
CDL light test with paper clip - pass
4wd sensor continuity - pass
CDL Actuator 9V test - fail

Does anyone know if a 3:1 t case gear set would delete or otherwise permanently lock the CDL?

Otherwise my conclusion is the actuator needs replaced. I did try tapping it and I cleaned all electrical connectors. The only thing that baffles me with this conclusion is why the CDL dash light would not come on.
 
Can you hear the actuator motor when you move lever?

If not,

Lower Xfer case a few inches, remove actuator. It’s not a difficult job by any means.
 
fjbj40 said:
Can you hear the actuator motor when you move lever?

If not,

Lower Xfer case a few inches, remove actuator. It’s not a difficult job by any means.
Click to expand...
Yeah I did the test where I unplugged its harness and hooked up a 9v battery and no actuator sounds. That’s why I’m pretty sure it’s the actuator that needs replaced. I can’t quite figure out why the light isn’t on though.
 
sgmartz said:
Yeah I did the test where I unplugged its harness and hooked up a 9v battery and no actuator sounds. That’s why I’m pretty sure it’s the actuator that needs replaced. I can’t quite figure out why the light isn’t on though.
Click to expand...
Despite your switch checking out it could still fail to function. Mine metered for continuity but after a load test it failed.

Unplug the switch, jump with wire and see if light comes on.
 
fjbj40 said:
Despite your switch checking out it could still fail to function. Mine metered for continuity but after a load test it failed.

Unplug the switch, jump with wire and see if light comes on.
Click to expand...
Yeah I did that and confirmed the light comes on with a paper clip jumper
 
sgmartz said:
Yeah I did that and confirmed the light comes on with a paper clip jumper
Click to expand...
Switch is fudged then, if your cdl is locked as you say.

This was my cdl dilemma

fjbj40

Thread 'Center diff locking'

I followed the instructions for locking center diff, but it’s not acting like it should.

I started truck, shifted to low, but I did not get the “ABS and diff lock” light.

ABS light comes on when I first turn on key but goes out in a few seconds.

I do not have a ctr diff switch, yet. But I thought it should lock if I did the low, get lights, pull 30 amp diff fuse?
 
fjbj40 said:
Switch is fudged then, if your cdl is locked as you say.

This was my cdl dilemma

fjbj40

Thread 'Center diff locking'

I followed the instructions for locking center diff, but it’s not acting like it should.

I started truck, shifted to low, but I did not get the “ABS and diff lock” light.

ABS light comes on when I first turn on key but goes out in a few seconds.

I do not have a ctr diff switch, yet. But I thought it should lock if I did the low, get lights, pull 30 amp diff fuse?
Click to expand...
When you say switch what do you mean? The CDL switch on the dash? Mine is a 97. Or the switch where the CDL plugs into the T case?
 
sgmartz said:
When you say switch what do you mean? The CDL switch on the dash? Mine is a 97. Or the switch where the CDL plugs into the T case?
Click to expand...
On the T case, the one that gets activated by the cdl shaft. Top fwd in the Xfer case
 
The 3-1 gears won’t change anything with the lights or CDL.
CDL should not be locking in 4 Hi
The switch is the same as a corolla five speed reverse light switch out a fraction of the cost.
It been a long day I’m sure I have a spare somewhere 😊 I will check after I get a shower.
 
Broski said:
The 3-1 gears won’t change anything with the lights or CDL.
CDL should not be locking in 4 Hi
The switch is the same as a corolla five speed reverse light switch out a fraction of the cost.
It been a long day I’m sure I have a spare somewhere 😊 I will check after I get a shower.
Click to expand...
That would be amazing!!
 
Here you go ;)
1758942797325.webp
 
Thanks all super helpful. I ordered that switch.

Just checking my logic. The switch replacement will ensure the dash light comes on.

However, my actuator still did not function with 9v applied so I need a new actuator or I could try to remove and rebuild mine. Agree?
 
If it indeed is not working you should be able to open it up and clean it. I have never worked on the center diff lock but have successfully opened up, worked on my rear diff lock and got it to work.
Again the center diff lock should not be on in 4 High. Also a front tire not spinning when jack up is not a indication of the CDL being engaged.
 
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