Another CDL problem (1 Viewer)

[YodaQuoia]

Typical disclaimer - I've searched and searched and haven't found a similar issue.

'99 LX470. When I push my CDL button the dash light (usually) comes on, I hear the relay behind the glove box click, and then without touching the CDL button I hear another click and the light goes off. Occasionally when I push the CDL button nothing happens - no click, no lights. Also, when I shift to 4L there is no light and no click.

This past weekend I pushed the CDL button, got the light/click, then the light went out on it's own. With the button still engaged I jacked up the DS front wheel and it spun freely so I understand from reading that this indicates the center diff is definitely not locked.

Thoughts on how to proceed with troubleshooting?

 

[Bisho]

One wheel may spin freely because we have open diffs, so that’s not a good test. If you try a tight turn you should feel binding if the CDL is locked.

Unless your truck was modded, 98/99 CDL should lock when the transfer case is put in low.

There is a switch on top of the TC to indicate the CDL is engaged, and it sounds like yours may be flaky.

 

[YodaQuoia]

One wheel may spin freely because we have open diffs, so that’s not a good test. If you try a tight turn you should feel binding if the CDL is locked.

Unless your truck was modded, 98/99 CDL should lock when the transfer case is put in low.

There is a switch on top of the TC to indicate the CDL is engaged, and it sounds like yours may be flaky.

The logic from the post I found recommending that test was that with the open front diff, power is sent to the wheel with least resistance. That would be the one off the ground during this test. If the CDL was engaged the wheel wouldn't spin by hand. Either way though, I only tried that test as a back up to trying the tight turn. Zero binding. I was just trying to confirm it wasn't engaged beyond that test.

How would I check for a mod that would make the CDL not engage when the transfer case is put in low? I haven't modded it but can't speak for the PO.

I read a little about the transfer case switches. Agreed they might be flaky, but will need to get the CDL working before really being able to diagnose those I think.

 

[Bisho]

Search for 7 pin mod, I believe. I have a 2000, so I haven’t done it, but I understand the mod decouples CDL from the TC position.

 

[Bisho]

reading your post, something else seems amiss. The CDL light should stay on. That light is 100% a direct indicator of the switch position on top of the TC case. So, the switch is bad or the CDL isn’t staying engaged.

You can pull the dash switch and check continuity to make sure it’s staying engaged. Are you confident it ever worked? I wonder if it’s jammed and not working mechanically. My LX was pretty sticky and very slow to engage/disengage when I got it. I changed the oil and engaged it daily for a week or two and now it’s like butter.

Did you notice when spinning the wheel if the front driveshaft was spinning? I’m fairly certain with 3 wheels on the ground and the CDL locked, the wheel will spin, but the driveshaft will not, because it’s locked to the rear wheels that are stopped on the ground. If the driveshaft spins with the wheel, that does confirm the CDL is unlocked.

 

[YodaQuoia]

Search for 7 pin mod, I believe. I have a 2000, so I haven’t done it, but I understand the mod decouples CDL from the TC position.

Thanks for that! If a PO has been messing with the system then it might be a wiring issue instead of a hardware one. Bigger pain in the ass but probably a cheaper fix.

 

[YodaQuoia]

For anyone who stumbles on this thread in the future - I just found the video below and this guy was having my exact issue. A new CDL switch fixed his problem. Guess I'll be trying this this weekend unless I find a wiring issue.