4WD No Awd, No 4Hi .. But 4Lo still works

[nopaybob]

Everything's been working until today
It does go into 2wh and 4Lo

Today I attempted to switch to 4hi.. both 4hi and awd did not work. The lights for both of these do not flash or illuminate either.

But 4Lo lights up and goes right into 4Lo when selected.

Can anyone point me to a similar thread or can help with my issue?

 

[The_Roadie]

Never heard of exactly that behavior, but the switch is the #1 suspect. Cheap even at the dealer.

 

[nopaybob]

Thanks, I was hoping to hear I needed to check a certain fuse or connection though
All the lights on the 4wd selector flash on startup. I just went out and tried smackin and wigglin the switch while turning it to awd and 4hi and got no lights or nothing for those two.
I will try the switch when able to pick one up.

 

[The_Roadie]

Yah, but the connection is inside the switch.

The lights that flash during the lamp test at start-up are entirely separate from the mode selection circuit. The TCCM drives the lamp AFTER it gets a mode change command from the switch, so if the contacts are dirty, the command resistance level isn't read properly by the TCCM and confusion results.

I assume, but didn't mention it, that you SHOULD be exercising your switch every few weeks, and turn it from end to end 100 or so times every few months, to make sure it doesn't build up oxidation and quit working. Before the Great Switch Redesign of 2005, they were more prone to this oxidation, but I assume everybody knows this from reading my posts for the last eight years.

 

[nopaybob]

this switch?

 

[The_Roadie]

That's the puppy.

 

[IllogicTC]

Yah, but the connection is inside the switch.

The lights that flash during the lamp test at start-up are entirely separate from the mode selection circuit. The TCCM drives the lamp AFTER it gets a mode change command from the switch, so if the contacts are dirty, the command resistance level isn't read properly by the TCCM and confusion results.

Or if the resistors went out for those two functions, somehow. Maybe one burnt up and took another with it?

 

[budwich]

IF you have the switch out, with a meter, you can readily test the resistance "bridge" setup by the switch at each position. This will either confirm your suspicions or point you elsewhere for a solution to your problem.

 

[IllogicTC]

I come bearing test values!

Using the harness for reference, there will be a pin that gets connected to a gray wire, and a pin connects to a light blue wire. Power enters the gray wire, and the impedance of the light blue wire provides the TCCM with selection data. I would imagine the test meter can be hooked up either way, it shouldn't really matter.

Place the switch in the 2HI position. The resistance should be about 240 ohms.
A4WD: 560 ohms
4HI: 1.1k ohms
4LO: 2.2k ohms
Neutral: 5.1k ohms. To test neutral, turn the switch to 4LO, then turn it clockwise a bit more until it stops, it'll go to a position that's unmarked. When you first start the vehicle, you'll notice a red N may light up on the far right, that's where you turn it to. Hold it there to get your reading.

If any of these values are significantly off, (let's say +/- 10% AT MOST), or have no continuity, the switch is toast.

 

[nopaybob]

I might need multi-meter 101, Everything read in the minus- and did not get a reading if I switched the red and black probes the opposite way on the gray and light blue wire. The first three were measured at 20k
4HI was the only value that came close
4HI -10.91
4LO -11.18
A4WD -10.17
2H -9.65
My local dealer doesn't have switch in stock till Thursday.
I took apart the switch and everything looked clean besides some grease. I went ahead and used some brasso on the back plug side and some 91% alcohol on the inside contacts. I can get all positions to lock in now, but If I am engaged in 4HI and switch to A4WD it lights up 2H.
I can only get A4WD to engage and light, by turning the knob slowly between 4HI and 4LO

I'm really hoping my third pic isn't a clue that it might be a related electrical issue instead, I have only seen that PRNDL1L2 light up a three times in the last 10,000 miles and the longest it lasted was maybe 5 minutes.

 

[The_Roadie]

1) Measuring resistance requires the switch to be disconnected from the vehicle. All you can measure with the switch connected to the harness would be voltage. That was going to be our next experiment, depending on what the resistance readings were.

2) The high voltage power supply in the instrument panel that drives the DIC and PRNDL display is totally separate from everything else here. It fails independently and never takes out anything else. Ebay is full of instrument panel repair services that can change stepper motors (if you ever have a lying needle) and those power supplies.

 

[budwich]

Its probably a good indication that you may have a few electrical issues. Probably not directly related other than as a possible cause... ie. poor connections.

Yes, you need to read up on measuring resistances with a meter....

 

[nopaybob]

Test values Thanks to lllogicTC
2HI 240 ohms
A4WD 560 ohms
4HI 1.1k ohms
4LO 2.2k ohms
Neutral 5.1k ohms



my RE measured values
2HI 237 ohms
A4WD 145 ohms
4HI 1.08k ohms
4LO 2.18k ohms
Neutral 5.03k ohms

I'll get a switch as soon as there in stock.

 

[budwich]

good testing... IF you got nothing else to do... you could try looking a little closer at the switch / wiper contacts assembly. Your measurements (and observation about slowly moving the switch to get the position to "register") appear to indicate that the 4awd position might just be contacting more than it should causing a "parallel resistance" measurement as opposed to a totally burnt / broken measurement. You might be able to "fix" the switch while you wait for the replacement.

 

[IllogicTC]

Anyone know the logic behind front actuator activation? Even with a shorted A4WD, 4HI still reads good in theory so it should command the TC to 100% clutch.. What I'm wondering is if every time the dial is turned does the system check to see if the front actuator is already activated, or just when switching into A4WD from 2HI?

I'm just curious because 4LO may not actually be 4LO but 2LO unless it double-checks every time the switch is turned. Just a pondering I have, kinda and kinda not related to the OP subject.

That aside it looks like when A4WD is selected, your contacts are likely actually touching both A4WD and 2HI contact points.

For two resistors in parallel, one 240 ohms and the other 560 ohms, the total resistance of the circuit is 168 ohms, which is obviously low similar to what your A4WD is showing. Taking a look at what budwich mentioned might provide an interim solution, but remember it's only interim, a new switch should still be installed.

 

[The_Roadie]

Anyone know the logic behind front actuator activation?

Not to that level of the algorithm. Easy experiment to do, given warm weather and time. I have one but not the other. Your situation might be reversed.

 

[IllogicTC]

Not to that level of the algorithm. Easy experiment to do, given warm weather and time. I have one but not the other. Your situation might be reversed.

Was the : cool : face a pun?

 

[Venturerick]

How do you get the switch out of the dash ?

 

[The_Roadie]

Pry it from the front. Two tangs on the sides.

 

[Venturerick]

Thanks Roadie for the quick reply.

 

[nopaybob]

I used a small flathead and put pressure on the different sides of the switch, no digging or nothing and it just popped out.