Center Diff randomly engaging while driving... (1 Viewer)

[haas]

The '00 LX470 has a new gremlin...The center diff lock keeps randomly engaging while driving. At first, I thought my knee accidentally hit the button, but alas, the problem keeps happening and the button is clearly still in the "off" or released position (popped out not pushed in).

After the center diff engages, it is EXTREMELY difficult to disengage. I try driving and reversing in a straight line, tight circles in reverse, jacking up the front and back on opposing corners...speeding around washboard dirt road corners seems to work the best at disengaging the center diff.

Today it came on and after a brief washboard jaunt, the center diff light turned off, but the VSC trac and VSC off lights remained on...I tried a few tight circles and it was pretty clear that the center diff was still engaged, even with the light off...AAAAAHHHHHH!

Any ideas on what might be causing the center diff to randomly engage while driving. Can I pull a fuse and turn the system off for now? And for the record, I am absolutely, positively, 100% certain that the button is not accidentally being pushed.

 

[Ayune]

@haas Easy things first: Pop off the dash panel where the CDL switch lives and unplug the switch from behind. If this solves the issue then your switch is simply bad and no amount of funny driving would help.

Also: Is the diff actually physically locking, or is just the indicator light turning on along with the other lights? If that's the case then the switch on the t-case may be bad.

 

[haas]

@Ayune....well that's an easy enough starting point. Now I just need to get the CDL unlocked before I unplug he switch. stay tuned...

 

[Ayune]

@haas I added an edit above re: is the CDL actually locked. You can unplug the dash switch reardless of the CDL state (locked or not).

 

[haas]

@Ayune, the CDL is definitely locking. You can feel the hesitation when the wheels are in full lock.

 

[Ayune]

@haas Correction: According to the wiring diagram you do need to keep the dash switch connected until the CDL disengages. After it disengages if you unplug the switch the control unit won't be able to run the CDL at all.

However, this won't pinpoint the problem because the dash switch must be plugged in to actuate the relays. You're trying to find out why it's engaging by itself and without the dash switch it'll never engage at all even if the fault lies somewhere else... So... I'd say replace the dash switch outright because it's simple and the only real way the control box will get a false signal to run the CDL motor. The control box doesn't have any real smarts in it and it needs to see 12V move from the Black wire to Orange wire to run the motor to "lock". Follow?

 

[Ayune]

@haas Looks like the dash switch is combined with the hazard switch: Toyota P/N 84014-60130, or "84014A" in this diagram: https://parts.toyota.com/images/parts/toyotaOEM/fullsize/a1_845621A.jpg

Costs about $52 online: 84014-60110 - Genuine Lexus Parts

 

[haas]

@Ayune. Makes total sense! Thanks for the wiring diagram. I am also worried about the actuator considering the problems I'm having getting the CDL to disengage.

To Do List:
1. Disengage CDL
2. Unplug CDL switch
3. Replace CDL switch
4. Hit the local trails with the CDL on and see if I have actuator issues
5. Replace actuator if necessary.

This LX has 275,000 hard miles on her...so I suppose these little gremlins will become more commonplace.

 

[Ayune]

I am also worried about the actuator considering the problems I'm having getting the CDL to disengage.

Hopefully that issue is solved with the new dash switch: If it isn't making proper contact to send 12V down the Black wire and into the control box, then the actuator motor will never be told to spin in the "disengage" direction. It's a $50 test to see if you have a $500 (or more) problem.

 

[Ayune]

@haas did you figure this out?

 

[haas]

@haas did you figure this out?

I've unplugged the CDL/Hazard board...and thats as far as I have gotten. Good news is the problem has disappeared

Bad news is I got distracted. While taking apart the cover to get at the circuit board, I decided it was time to replace all the burnt out bulbs in the climate control system....I ordered some el cheapo amazon LED's with good reviews and they didnt fit. The base on the T4's was right, but the led wouldn't fit through the hole in the circuit board. Then the t5's were an awful green color...FAIL! On top of that I'm currently wrapping up a dana 60 SAS under my old chevy.

I'll get back to the LX in a week or two and report back!

 

[Ayune]

I'd rather work on a SAS than change tiny light bulbs too!