1999 Limited New to Me - Questions

[Cmayer]

1999 Limited 4wd - no indicator lights

All right, picked up a '99 limited 4x4 with multi-mode 4x4 and rear locker. Truck has all the options, but some of them aren't working lol. I knew it would need some work and I have no issue doing it. However, through searching I have some questions that I haven't figured out yet.

1. 4x4 indicator doesn't illuminate anything in any position. 4x4 doesn't work.
a. 4x4 with center diff unlocked (awd multimode) doesn't do anything.
b. 4x4 H doesn't do anything. Turned tight on dry ground and didn't get a binding feeling.
c. 4x4 L increases torque feeling, but again no tire binding in parking lot.

Any reason that the 4x4 system wouldn't work at all? I've read lots of threads where the indicator light on blinks and how to check all the switches. In my case it doesn't even light up. Might be a bulb, but all other bulbs work...

 

[Cmayer]

Checked the VSVs and neither are receiving vacuum. The vacuum port off the engine with the check valve has vacuum.

My guess is an electric switch isn't working somewhere. Time to get the multimeter out. Sucks that I'm traveling the next few days.

 

[audiness]

I had the same problem when I bought my 2000 4x4. It seems that the vaccumm lines to the VSVs are very sensitive to having any leaks. I found a small leak in one of my lines. Also, I followed the wire leads that go into the sensors in the transfer case. I took out the sensors (3 I believe) cleaned them, lubricated them, and made sure they all worked with my multimeter. My 4wd works fine now.

 

[Cmayer]

I checked the vacuum lines and they held vacuum from the VSVs down. One engaged the front diff actuator and the other released it both at 25 mg vacuum.

I pulled the front diff switch/sensor and it jumped all over on the ohm meter, but did show continuity.

Checked the two switches/sensors on the transfer case actuator and they read good on the ohm meter 0.8 front switch and 0.0 rear switch.

I don't have a 27mm wrench, so I can't get the two high up on the driver's side. I think they're the 4h and 4l switches. Also can't get to the one on the passenger side, the center diff lock switch.

I put power straight to the transfer case actuator and it moved freely. Reversed polarity and it came back out fine too.

So here's where I am:

VSVs - No power / no vaccum.
Vacuum lines - hold vacuum.
Front diff actuator - switches in and out with vacuum.
Transfer case actuator - switches in and out with direct power.
Front diff sensor/switch - can't get a good reading on the ohm meter. Don't know if 80-134 reading is good or bad.
Rear transfer case switches - Read close to the same 0.0 - 0.8. Guess that's good.
Can't get to the other switches yet.
Nothing has caused the dash indicator to light up at all.

 

[Singtoe]

With the indicator lights not blinking, it kind of tells me something is wrong with the 4x4 ECM. Either it has no power, no ground or a bad ECU.

If the VSV valves were bad or no vacuum, it would blink.
If the Acuator was corroded or seized, it would blink.
If the ADD was stuck, it would blink.
If the switches were bad, What is the likelyhood that two go bad at the same time.

Find the 4x4 ecu and check for power (12 volts) at the black wire with white stripe. Check your grounds ( white wire with black stripe) for grounds. either a ground checking led tester or using the multimeter and looking for continuity between it and the body.

 

[Cmayer]

Checked the 4wd ECU part number 89533-35070

Black with white stripe has power
White with black stripe has continuity to ground
Blue with yellow stripe also has power to it.

I also rechecked the front diff actuator switch after cleaning it and it read 0.8 ohms now. Much better and consistent. Too bad it didn't make a difference.

Right below the 4wd ECU inside the driver's side kick panel is a large white female connector that has nothing to plug into. I noticed it has power at a few terminals too. Any idea what that is? There's nothing near it that it could possibly connect to.

I've checked every fuse by eye, test light, and multimeter. They all test good.

 

[Cmayer]

Spent the day on this and didn't make any progress; frustrating.

Here's the white connector at the base of the driver's side kick panel. Anyone know what this is?


Replaced all fuses and no change.

Checked the 4wd button on the transfer case shifter and it checks out fine.

I can make everything work by rigging it:
Front actuator works fine with vacuum to the upper lines both in and out.
Transfer case works fine with power straight to it.
Low range works.

Just stuck on making everything turn on and work together.

 

[Singtoe]

Spent the day on this and didn't make any progress; frustrating.

Here's the white connector at the base of the driver's side kick panel. Anyone know what this is?


Replaced all fuses and no change.

Checked the 4wd button on the transfer case shifter and it checks out fine.

I can make everything work by rigging it:
Front actuator works fine with vacuum to the upper lines both in and out.
Transfer case works fine with power straight to it.
Low range works.

Just stuck on making everything turn on and work together.

The white plug is for an optional rear e-locker ECM.


As for you problem, The 4x4 ECM sounds like its bad. because if the actuator was bad, the dash lights would blink in malfunction. You have power and ground continuity and your switches work, the ECM is all that is left.

 

[Cmayer]

The white plug is for an optional rear e-locker ECM.

I have the rear e-locker and it works fine. Is this for a different type of install from the factory? I tested the e-locker in the dirt and with the truck in the air. Low range and the e-locker works as they should.

As for you problem, The 4x4 ECM sounds like its bad. because if the actuator was bad, the dash lights would blink in malfunction. You have power and ground continuity and your switches work, the ECM is all that is left.

That's what I'm thinking too. New isn't cheap and used aren't out there right now. Checked a few junk yards and couldn't find one local. Will keep an eye out on the regular sites for one.

I keep finding reference to an ADD relay, but I can't locate it. The 2000 manual says it's tucked inside the passenger side kick panel somewhere.

 

[Singtoe]

That plug is for your 4x4 ecm then. It is missing, thus why it doesn't work.


Non limited's have the ADD Relay pack in the pass kick panel area.

 

[Cmayer]

I guess missing a computer would be a bad thing.

I know for sure that I have:
89533-35070 Computer 4 wheel drive. It's a black box and is tucked up high behind the driver's kick panel attached to the firewall.

I assume now that this is just for the locker and ABS interface.




Which would mean that I'm missing:
89533-35150 Computer 4 wheel drive. Appears to be a silver box, but that's all that I can find.

Can anyone confirm that the missing ECU is part number 89533-35150 for a 1999/2000 limited 4x4?

 

[Coast2Coast]

I guess missing a computer would be a bad thing.

I know for sure that I have:
89533-35070 Computer 4 wheel drive. It's a black box and is tucked up high behind the driver's kick panel attached to the firewall.

I assume now that this is just for the locker and ABS interface.




Which would mean that I'm missing:
89533-35150 Computer 4 wheel drive. Appears to be a silver box, but that's all that I can find.

Can anyone confirm that the missing ECU is part number 89533-35150 for a 1999/2000 limited 4x4?

I have a 99 limited with the same systems as yours I can check and see what mine looks like after work if nobody else does by then.

 

[Cmayer]

I have a 99 limited with the same systems as yours I can check and see what mine looks like after work if nobody else does by then.

If no one else has, I'd appreciate it if you could pull the kick panel real quick.

 

[Coast2Coast]

Well there's your problem:



:redbrick:

 

[Cmayer]

Yep , that explains it. Thank you for the picture!

 

[rideexileex]

Ha, I know this isn't going to be appreciated by any technical means, but I think that's a first for a non-functional 4wd system.... "Install computer"

 

[Cmayer]

Ha, I know this isn't going to be appreciated by any technical means, but I think that's a first for a non-functional 4wd system.... "Install computer"

It was so obvious, that I refused to believe that was it :shrug:. Plus the previous owner swore he took it out just a few months prior and used 4wd. I called him on the computer and he truly knows nothing about it; I trust him and I'm not a trusting person by nature.

Right before I made the purchase a potential buyer took it for an inspection and the owner wasn't there. I think that during this inspection the computer went missing.

Oh well, I thoroughly checked the rest of the system that was there. :redface:

I'll have to save this one for an April 1st thread in the future.

 

[Cmayer]

New to me 4wd computer, thank you DeathCougar.