4wd electrical issue

[TheDurk]

Thanks for posting the EWD. It helps me understanding what I'm actually doing.

I did a couple more quick checks over lunch. With the truck running I cycled the 4wd button and checked T26 and T13 at various intervals (checked each while engaging 2wd and 4wd). Neither terminal gave me any response.

With both VSVs unplugged (electric) and the 4wd button depressed the front prop turns freely. This doesn't surprise me because the VSVs don't have any power anyway and now that the brown VSV isn't stuck open no vacuum passes through either VSV.

Tonight I'm going to check the connections to the 4wd button just to be sure that it's actually functioning. When I bought the truck the driver's side power seat didn't work because the power wire had been severed, maybe they disconnected the 4wd selector as well.

I'm very close to just buying another 4wd ecu to try but I can't even find one for sale at the moment.

Yeah, but it tells you the T/C actuator is not engaging either. I was expecting it to lock from the back (T/C) end, not the front (ADD) end. Checking the button is a good thing, because the lack of 12V+ to T26 and T13 means the T/C actuator is not even getting the signal to TRY to engage. So no surprise it doesn't. I'm thinking it's either the button or the 4wd ECU itself at this point. I don't see any other possibilities. We could test the actuator, but that would be nice-to-know at this point. We have to get the ECU to respond to the button and send voltage to the T/C actuator.

Do you get ground on the pink wire at Pin 4 of the ECU with 2-4 switch engaged?

Have you ever unplugged the 4wdECU? If not, do so, just for fun. Clean the contacts while you are in there--you never know. What is the p/n on your ECU; I get three possibles and no discrimination:

89533-35070 PART NUNBER LABEL=89533-35070
89533-35150 PART NUMBER LABEL=89533-35150
89533-35170 PART NUMBER LABEL=89533-35170

 

[ScubaS]

To my surprise the pink wire gets ground with the 4wd button engaged. I guess that means the button works!

I have unplugged the ecu a few times and I cleaned the contacts with electrical cleaner to no avail. The ecu is the one ending in 150. I found one on eBay for $35 so I took the chance and ordered it.



Edit: forgot to mention that I confirmed that t18 does not get ground.

 

[IBallEngineer]

To my surprise the pink wire gets ground with the 4wd button engaged. I guess that means the button works!

I have unplugged the ecu a few times and I cleaned the contacts with electrical cleaner to no avail. The ecu is the one ending in 150. I found one on eBay for $35 so I took the chance and ordered it.



Edit: forgot to mention that I confirmed that t18 does not get ground.

My money is on the ECU. I haven't had time to truly try to solve this, but I've followed the logic and I think [MENTION=10169]TheDurk[/MENTION] is on target, as you are in ordering that one at that price.

:cheer2:

 

[TheDurk]

To my surprise the pink wire gets ground with the 4wd button engaged. I guess that means the button works!

I have unplugged the ecu a few times and I cleaned the contacts with electrical cleaner to no avail. The ecu is the one ending in 150. I found one on eBay for $35 so I took the chance and ordered it.



Edit: forgot to mention that I confirmed that t18 does not get ground.

Yeah. We have no other choice at this point. Button is good. Has to be ECU. $35 is a great price. Please report back when you try it.

 

[ScubaS]

Yeah. We have no other choice at this point. Button is good. Has to be ECU. $35 is a great price. Please report back when you try it.

Will do. It probably won't arrive until early next week. I hope this works!

 

[ScubaS]

Well the new ECU didn't make any difference so far. I haven't tested anything or even driven it yet but the lights are still flashing with the truck running. I'll start running some checks tomorrow but I'm not hopeful.

It's possible that I have two bad ECUs but I don't think that's the case.

 

[TheDurk]

Well the new ECU didn't make any difference so far. I haven't tested anything or even driven it yet but the lights are still flashing with the truck running. I'll start running some checks tomorrow but I'm not hopeful.

It's possible that I have two bad ECUs but I don't think that's the case.

Well, the real test is if you get a signal on T13 and T26 when you switch. If you do, new ECU is working but actuator is not responding. If you don't, then I assume some input it is receiving is keeping it from trying to actuate the T/C and I don't know what that is. Don't give up. Still a few things to try.

Please check for ground on Pins 6,7, 18 & 19 in 2wd and 4wd. By the way, I assume Diff Lock SW is off through all this, right?

 

[ScubaS]

Well, the real test is if you get a signal on T13 and T26 when you switch. If you do, new ECU is working but actuator is not responding. If you don't, then I assume some input it is receiving is keeping it from trying to actuate the T/C and I don't know what that is. Don't give up. Still a few things to try.

Please check for ground on Pins 6,7, 18 & 19 in 2wd and 4wd. By the way, I assume Diff Lock SW is off through all this, right?

I'm still getting no signal at T13 and T26 with the new ecu (truck running and alternating 2wd/4wd button). I'll check those grounds as soon as possible. I might wait until it warms up a little outside.

Diff lock has been off the entire time. I tried putting it in 4L and pressing diff lock while parked to see what happens. The ABS light came on and the diff lock light started flashing. I also tried to shift to 4Hi above 62mph to see if the warning buzzer would go off and nothing happened.

 

[TheDurk]

I'm still getting no signal at T13 and T26 with the new ecu (truck running and alternating 2wd/4wd button). I'll check those grounds as soon as possible. I might wait until it warms up a little outside.

Diff lock has been off the entire time. I tried putting it in 4L and pressing diff lock while parked to see what happens. The ABS light came on and the diff lock light started flashing. I also tried to shift to 4Hi above 62mph to see if the warning buzzer would go off and nothing happened.

Ok. I have some new info. I told you I'm a 5-speed guy and now you are paying the price. I found the FSM that covers your T/C. T13 and T26 don't get voltage to ground, they get it TO EACH OTHER, one way for engage and the opposite way for disengage. Duh! I should have figured that. Sorry. The relevant part of the 2002 FSM for the T/C case actuator linked below is identical to what I have in my paper FSM for the multi-mode for '99, so it applies. The key page is the standard readings page, TR-53. You should go through that whole thing, and see what you get compared to standard. Also the tests of the T/C actuator starting at Section 4 on page TR-50. It shows you how to use your heater relay to test fire the actuator.

Again, I have a J-shift so I haven't done any of this. I know the 5-speed system cold, and the vacuum ADD, but not this stuff. If any slushboxer out there wants to help us out, feel free to chime in.

 

[ScubaS]

Whoops. No worries it's actually somewhat of a relief to know that there's new path to follow. It's probably time for me to pick up a DMM.

 

[IBallEngineer]

Wow, where did you find the test(s) pages? Who knew they would have such a simple thing be so complicated.

 

[ScubaS]

Ready for things to get weird? I started running through the 4wd ECU checks from page T-53 and was getting some bad results (see below). I decided to pull some QDs on the actuator and spray them with some QD cleaner. I cleaned three of them that are near each other on the actuator, I'm not exactly sure which plugs they are. Here's the weird part, I checked the VSVs and they now both have power. The blue (4wd) VSV has vacuum and the brown (2wd) VSV has no vacuum (this was the the one that had issues before so I assume it actually is bad). The truck is now in 4wd and the 4wd light is still flashing. I don't know if I did something while prodding the 4wd ECU or if it was related to cleaning the QDs.

I can't rotate the front prop so I assume that means the center diff is locked and I'm in 4wd not multimode, does this sound right? I don't want to drive it around in 4wd so I'll probably have to manually switch it back to 2wd.

I didn't get many results from the ECU testing because I'm confused by some terminology. How do I control ADD lock and ADD free? What I can say for sure is that T6(4wd) - T25(GND) has 10+ with 2-4 switch on and it should not. T9(TL1) - T25(GND) has 0.2V with center diff lock switch on and it should have 10+. Sorry for the partial data, I wanted to post right away due to the change in the VSV situation.

 

[TheDurk]

Ready for things to get weird? I started running through the 4wd ECU checks from page T-53 and was getting consistently bad results (see below). I decided to pull the QD on the actuator and spray them with some QD cleaner. I cleaned three of them that are near each other on the actuator, I'm not exactly sure which plugs they are. Here's the weird part, I checked the VSVs and the now both have power. The blue (4wd) VSV has vacuum and the brown (2wd) VSV has no vacuum (this was the the one that had issues before so I assume it actually is bad). The truck is now in 4wd and the 4wd light is still flashing.

I can't rotate the front prop so I assume that means the center diff is locked and I'm in 4wd not multimode, does this sound right? I don't want to drive it around in 4wd so I'll probably have to manually switch it back to 2wd.

I didn't get many results from the ECU testing because I'm confused by some terminology. I know what the 2-4 switch is but what is the touch select center diff lock switch?

No, it may just be locked from the front, since there is vacuum on the 4wd hose. It can lock up from either side. To work in 4wd, it has to lock from both sides, of course. I don't know if you can turn it by hand in multi-mode AWD with the ADD disengaged. I don't have one, as I said. But it sounds to me like the ADD should be engaged and locking it from the front.

I assume the center diff lock switch is what is activated when you put that shift lever in H4L. But I've never even seen one of these things so I'm guessing.

 

[ScubaS]

No, it may just be locked from the front, since there is vacuum on the 4wd hose. It can lock up from either side. To work in 4wd, it has to lock from both sides, of course. I don't know if you can turn it by hand in multi-mode AWD with the ADD disengaged. I don't have one, as I said. But it sounds to me like the ADD should be engaged and locking it from the front.

I assume the center diff lock switch is what is activated when you put that shift lever in H4L. But I've never even seen one of these things so I'm guessing.

Any thoughts on why both VSVs would be getting power at the same time? That one has me confused.

 

[TheDurk]

Any thoughts on why both VSVs would be getting power at the same time? That one has me confused.

Having ruled out the ECU, I am as baffled as you are. You would think it would fail-safe to 2wd, i.e. vacuum on only one side.

 

[ScubaS]

Having ruled out the ECU, I am as baffled as you are. You would think it would fail-safe to 2wd, i.e. vacuum on only one side.

Big update! I spent some time doing some more poking and prodding today trying to figure out why both VSVs were seeing power all the time. I unplugged every harness I could find between the 4wd ECU and the VSVs and this seemed to convince the "new" 4wd ECU to work! I'm still having an issue with the VSVs not switching (both have power but only the blue 4wd VSV has vacuum right now) but I can now hear the 4wd ECU clicking when I shift from 2-4.

Here's the weird thing, when the 4wd ECU first stated to work the flashing 4wd light went out when I was in 2H but flashed again when I pressed the 2-4 switch or tried to shift into 4H (center locked). After that I decided to test the tc actuator by applying direct power. The tc actuator engaged and disengaged as it should (at least I could hear it moving). After that I get flashing 4wd lights in 2H but depressing the 2-4 switch lights the 4 tires green and turns out the center diff light. Shifting into 4H (center locked) makes the lights flash again. The blue VSV is still the only one with vacuum and I believe they both still have power (need to double check).

About the VSVs, what's really bizarre is that the brown (2wd) VSV works fine when I jump it with the battery but it doesn't work when I connect the plug to it (which has 11.3V). When the light stopped flashing in 2wd, the brown VSV had power and vacuum and the blue did not. I really have no idea what is making the VSVs go haywire.

Sorry if this post is ridiculously confusing. I'm attempting to describe a bizarre situation, actually a few bizarre situations.

 

[IBallEngineer]

**scratches head**:smokin:

Sadly I haven't followed closely enough to be up to speed, even with my limited familiarity. No way I would say I really "get it" on this one. I'll continue to provide encouragement from the peanut gallery. Somethin's gotta give here.

:cheer2:

 

[ScubaS]

Encouragement is always welcome. At this point I'm thinking there is an issue with the tc switch since the VSVs aren't switching. It must be sending some screwed up signal that's powering both of them.

There's no doubt that I had more than one issue here. I feel like I'm getting back into normal "4wd not engaging" teritory.

 

[TheDurk]

Encouragement is always welcome. At this point I'm thinking there is an issue with the tc switch since the VSVs aren't switching. It must be sending some screwed up signal that's powering both of them.

There's no doubt that I had more than one issue here. I feel like I'm getting back into normal "4wd not engaging" teritory.

Well, you have succeeded in confusing the heck out of me. But I think you are on the right track. If two ECU do the same thing, then the inputs must be in 'does not compute' territory.

Thing with T/c switches is there are two for 4wd, one for 4H and one for 4L. But it's time to check them all anyway.

My off the wall theory is your T/c actuator is stuck. It can go into 4HF fine, but it is unable to get to 4HL, i.e. it can engage the front shaft, but it can't lock the center diff. How about 4L? Does that engage now?

It occurs to me your VSV issue may be ground-related. (Durk's Rule #7 of electrical troubleshooting: 7. Weird fails usually involve grounds.)

The VSV's use a separate ground to Point EB. The rest of the circuit grounds to IF high up in the right cowl. There may be resistance between the two. EB is the fender ground that has a cable to the battery. It probably worth pulling that and cleaning up the fender to bright metal, shining up the terminals, and slather the whole thing in petroleum jelly. Then apply German torque to the bolt. The nasty rust on the VSV bracket suggests this is a good idea even if it doesn't fix this problem. (PJ conducts, so that is what I use on ground points and battery terminals--dielectric grease on everything else.)

At this stage, doing the cowl one is probably worth it, too, if it is not too hard to get to. The attachment shows where these grounds are on page 36 and 38. It's for the 2002, but it is exactly the same in my paper '99 EWD. Since it is inside, there shouldn't be corrosion, but it might be loose.

For what it's worth, you are making progress. When this is over, I'm letting you answer all these 4wd questions from now on, especially regarding slush boxes.

 

[ScubaS]

Well, you have succeeded in confusing the heck out of me. But I think you are on the right track. If two ECU do the same thing, then the inputs must be in 'does not compute' territory.

Thing with T/c switches is there are two for 4wd, one for 4H and one for 4L. But it's time to check them all anyway.

My off the wall theory is your T/c actuator is stuck. It can go into 4HF fine, but it is unable to get to 4HL, i.e. it can engage the front shaft, but it can't lock the center diff. How about 4L? Does that engage now?

It occurs to me your VSV issue may be ground-related. (Durk's Rule #7 of electrical troubleshooting: 7. Weird fails usually involve grounds.)

The VSV's use a separate ground to Point EB. The rest of the circuit grounds to IF high up in the right cowl. There may be resistance between the two. EB is the fender ground that has a cable to the battery. It probably worth pulling that and cleaning up the fender to bright metal, shining up the terminals, and slather the whole thing in petroleum jelly. Then apply German torque to the bolt. The nasty rust on the VSV bracket suggests this is a good idea even if it doesn't fix this problem. (PJ conducts, so that is what I use on ground points and battery terminals--dielectric grease on everything else.)

At this stage, doing the cowl one is probably worth it, too, if it is not too hard to get to. The attachment shows where these grounds are on page 36 and 38. It's for the 2002, but it is exactly the same in my paper '99 EWD. Since it is inside, there shouldn't be corrosion, but it might be loose.

For what it's worth, you are making progress. When this is over, I'm letting you answer all these 4wd questions from now on, especially regarding slush boxes.

Actually the two ECUs do not do the same thing. The old ECU continues to do nothing, the new one is working. Originally, neither of them were working but for whatever reason the new one started to work while I was messing around with wires.

I'll clean the grounds that you mentioned, thanks for the diagram. I find it really bizarre that I can power the brown VSV directly but it doesn't work when I connect the harness (which has 11.3V). I still haven't ruled out the possibility that the male plug isn't making proper contact with female VSV end. That still doesn't explain why they both have power. I thought there might be short somewhere that caused them to always have power but I've since confirmed that they're getting it from the 4wd ECU.

Anyway, I'll pull and clean the TC switch connections to see if that helps. I haven't tried 4L since the ecu started to work. I'll check it tonight.

As the situation gets more bizarre my posts sound more and more like disillusion rambling.