2002 xls brown wire mod

I've been frustrated with strange pulsating sometimes under hard acceleration - I think it's the strupid control-trac. So I'm pursuing the brown wire mod on my 2002 XLS. I'm going to put in the lighted 30 amp switch I've read about in this forum. I'm planning on getting to the brown wire that is found behind the glove box. A few comments and questions:

1) I have the ford wiring manual. I think there's a mistake. They have the c281a and c281b connectors identified backwards in the manual. The wires for each are described properly but they are switched in the manual. I'm on a trip now and don't have this info with me, but I know they are reversed.

2) In wiring this switch, there are 3 connections - ground, power and load. I presume we want to run the brown wire from power to load and connect the ground lead to the load lead. I think the idea is to have the internal light in the switch carry the current that flows through the brown wire. When the switch is off, no current flows and the light is off. With the switch on, depending on the current flow, the light intensity is controlled.

Thanks for your comments,
Tom

Are you going to address the Pulsating? The brown wire mode will keep you 2wd, but what about making sure your 4x4 mode is ok first. I have no pulsating under heavy acceleration, in rain or dry pavement. Maybe you have an issue with your transfer case.
I plan to do the Brown Wire mod in a month or so. GOOD LUCK!

I've been able to hear my pulsing at wide open throttle since mine was new in '98. Some people hear it, some don't.... no rhyme or reason, but they all work the same.

You don't want the light in the switch to try and carry that load as it's not capable of doing so, and the transfer case may or may not engage. The light in the switch is a very, very low current draw. You want the light in parallel with the power flow to the clutch coil, not in series.

Power from the TOD relay goes to the power terminal on the switch, the other side of the brown wire goes to the load connection on the switch, and the ground for the LED goes to the ground. If you get annoyed by the light, you can disconnect the ground and the switch will still work, just not light up.

-Joe

Did the brown wire mod - strange behavior!

Ok - I did the mod and it works - with reservations. With the switch in the "on" position, the light is very faint in the auto position and bright in either the 4wd low or 4wd high positions. If I then flip the switch to the "off" position, the light goes off. However, then every so often the 4x4 high dash light will flash about 10 times. To reset the system and get the control trac system to work again, I have to turn the engine off and back on, witht the new switch in the "on" position. So I think the switch works, but I now have an annoying 4x4 high dash light that flashes. What I want to do is to leave the switch in the "off" position, and put it on prior to activating 4 wheel drive. But to do this, I'd then have to turn the car off and on again to re-set the control trac system. Suggestions?

I did this to my 2002 XLS. I spliced the brown wire on terminal 8 of the C281A relay behind the glove box. Supposedly this feeds the 4WD clutch solenoid.

Thanks,
Tom

Well, it would appear that this might be a bit more complicated than I first thought. It would appear that the 4wd control module is set up to receive a feedback signal from the transfer case clutch coil. On the 2nd generations, the coil simply grounds. Apparently on the 3rd gens, the coil grounds, but connected to that ground is a BN/YE wire(early build) or a OG (late build) wire that connects back to the 4wd module via terminal 17. The wiring may be a bit more elaborate, but could work.

Without having one to test with a multi-meter, there's a chance that feeding a full 12V back into it could cause a melt-down. But, I think that if you added a second ground wire from the switch's ground for the light, and spliced that in with the wire I mentioned above, it might provide just enough feedback to make the control module happy.

Again, this is a wild guess..... I honestly don't know if it'll work or not. Without having a way to break that wire and see what exactly its purpose is, I honestly don't know. That wire could very well be the ground for the whole module that just happens to share a connection with the clutch coil.... Again, I don't know.

-Joe

edit: Found some new info.....

Here's something else to consider...... there are two different diagrams depending on the build date (early versus late). You mentioned that you used the brown wire on terminal #8 from C281A.... according to my prints, if it was a brown wire in terminal #8, it was C281B for an early build. The late build shows the brown wire being from connector C281a and the #8 is an orange wire.

For both the early and late models, it lists the brown wire as being the 'Four-wheel drive control module to Differential Lock Solenoid' which makes sense. In either case, the 'other' wire connected to the transfer case is labeled in the connector pin-out as being the "Four-wheel drive control module to transfer case assembly" wire. That doesn't help much though as it doesn't really explain what it does.

But..... as near as I can tell, if your brown wire was on terminal #8 of C281b, that would indicate that you have an early build, and the 'other' wire that may be causing the problem could be the brown/yellow wire on terminal #17. (directly below #8 when looking at the connector)

Looks like we've got some more trial and error to do, huh?

-Joe

more info!

Hi Joe,

Well, I guess it was C281B and my memory must not be perfect! It was definitely #8 and definitely a brown wire. As I said in my earlier post, the connector location diagram in the wiring manual had the 2 connectors, C281A and C281B reversed.

Also, according to the manual, the clutch coil does NOT go directly to ground but goes back to the 4wd control module. Hence, the problem with the 10 flashes of the 4x4 light.

But GOOD news! Tonight was the first chance I really got to drive the car and test the system. The good new is that the pulsating I feel under hard throttle (up a hill) is definitely the control trac system, because the light in the switch pulsated from dim to bright as I felt this pulsation. So, this is definitely the fix to that wierd problem.

Now, to figure out how to turn off the control trac without getting the 4x4 dash light flash and without having to turn off/on the engine to re-set the control track and 4 wheel drive. I reviewed the wiring schematics in the 2002 wiring manual and could not obviously see how to do this. I'm tempted to try the 2 ground wires, i.e., switch them. Oh, for the simple old manual 4wd days.

Any more ideas?

Thanks,
Tom

In my schematic for your truck (which is coming right off the Ford servers, page 34-4 specifically) it shows two wires running to the transfer case clutch coil: The brown wire and a brown/yellow (on terminal 17, directly below the #8 brown wire), and a separate ground connected to both of them, but no connector, as though it's an internal ground in the transfer case itself. I wouldn't put any faith in that one though as it doesn't make much sense.... unless there was a solid-state amplifier/relay, I don't see that working.... but I digress.

What I would do is break the brown/yellow wire in the dash next to the spot you interrupted it for the brown wire (I'd use a pair of bullet connectors in case you need to return it to stock). Then connect a digital multimeter to the two halves. Set your switches for automatic mode, then check the polarity on the brown/yellow wire. If the power is flowing from the module to the transfer case, we'll have to do some more figgerin'. If the power normally flows through that wire from the t-case back to the module, you'll need a different switch to make it work..... an SPDT switch may do the trick if that's the case, but again, we'll have to do some more figgerin.

Also, if your meter will support it, see if you can determine how much current is flowing through that wire when the transfer case has 4 high engaged. That'll give me an idea of what we need to do to make it work (i.e. if we need to feed it large amounts of current, or just voltage).

Let me know what you find out. Good luck!

-Joe

Thanks for your comments Joe. I will be checking this sometime between now and the weekend. You have the wires correct. Yes, I have a digital multimeter and can do the checks you suggest.

Thanks again!
Tom

Good! Let us know what you find out.... We may be pioneers for all the 3rd gen owners out there.

-Joe

ooooh, the suspense is killing me!!!

-Joe

Hey Joe,

Me too!! I have too much going on and know I won't have a chance to check it till Saturday. I know this is the fix for the "thumping" thing under hard acceleration, because the light is telling me the control trac is trying to function properly in these situations. This also tells me either that the control trac system is pretty bad or that I have a fault somewhere in mine. I read somewhere a post re the 4x4 control box being faulty in the early 2002's - so I'm wondering if that could be where the problem lies.

I have other good news re a pinging problem I was experiencing. I did the following - replaced both front O2 sensors, replaced EGR valve, cleaned MAF sensor, disconnected battery for more than one hour, reconnected battery and (probably unrelated) degreased engine. After about a day of driving the pinging is all gone!! This is amazing! I believe one key to this was disconnecting the batt so the cpu could relearn.

Now...after degreasing the engine (good old Gunk) I had pulley noise and I'm keeping my eyes (really ears) on this one.

Thanks and will keep you posted!
Tom

awsome guys.... nail it nail it. I understand about half of what you guys are talking about, lol, but power to you. Im dying to install the mod.

Im still in break-in mode on my new motor....

With this mod ill launches at the strip in 2wd mode....

Keep up the good work!!!

awdrocks said:

With this mod ill launches at the strip in 2wd mode....

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Like I said in the other post, there's really not much of an advantage to launching in 2wd mode if you still have to push the front half of the drivetrain down the road anyways. Since it's got to be rolling anyhow, you might as well use it to help propel you down the track.

Just my .02

-Joe

yeah im TOTALLY for AWD launch. Unstoppable!!! But im afraid that all the added power I have will bust the weak TC. All the power tranfer when it engages and disangages can most likely snap it like a twig. But AWDHigh might be the ticket. For now.

I spoke to Border Parts in Cali and he has a bullet proof tranfer case that will bolt right on. It can handle up to 700hp more or less.

With this TC, a rebuilt stronger tranny, stronger half axles, 4.10s etc... once thats done im going to do more engine work (heads, cams etc), get a nice stall converter, nitro.... then walaaa.... AWD will launch so hard it will be insane.... im shooting for 11's

awdrocks said:

yeah im TOTALLY for AWD launch. Unstoppable!!! But im afraid that all the added power I have will bust the weak TC. All the power tranfer when it engages and disangages can most likely snap it like a twig. But AWDHigh might be the ticket. For now.

I spoke to Border Parts in Cali and he has a bullet proof tranfer case that will bolt right on. It can handle up to 700hp more or less.

With this TC, a rebuilt stronger tranny, stronger half axles, 4.10s etc... once thats done im going to do more engine work (heads, cams etc), get a nice stall converter, nitro.... then walaaa.... AWD will launch so hard it will be insane.... im shooting for 11's

Click to expand...

Completely dumb question, but do you have the AWD transfercase or the Control Trac?

IAmTodd said:

Completely dumb question, but do you have the AWD transfercase or the Control Trac?

Click to expand...

Yeah...I was thinking the same thing. I'm not sure about 3rd gens, but for 2nd gens the brown wire mod only works with control trac 4WD and does not work with AWD.

Lee S. said:

Yeah...I was thinking the same thing. I'm not sure about 3rd gens, but for 2nd gens the brown wire mod only works with control trac 4WD and does not work with AWD.

Click to expand...

well your probably right... i might be wrong by saying AWD. 3rd gen has control trac 4WD (4X4Auto, when rear spins front locks) and permanant 4X4 (4X4High, front and rear always locked, or AWD to me)

The mod is done to 4X4Auto or control trac in that case

Hey Joe,

I started playing with my multimeter and separate clamp on ammeter attachment (which I've never used) to try and check the surrent flow in both the brown wire and the brown/yellow wire. I'm testing the darm clamp on device and not getting any reaction (using ac wires feeding lamps in my house). I'll keep working this one. Also, I re-read your last post re possibly using a SPDT switch. Wouldn't I want to use a DPST switch to turn off both B and B/Y wires? One option would be a DPDT switch where I put in a dummy load to simulate the transfer clutch solenoid in the "off" position. That occured to me today - that I could trick the system into thinking it is seeing the transfer solenoid (so it won't flash the 4x4 light!) when it is really not active. I'll keep working the problem - this weekend I'm not having as much time as I wanted to work on this issue.

Thanks!
Tom

awdrocks said:

well your probably right... i might be wrong by saying AWD. 3rd gen has control trac 4WD (4X4Auto, when rear spins front locks) and permanant 4X4 (4X4High, front and rear always locked, or AWD to me)

The mod is done to 4X4Auto or control trac in that case

Click to expand...

The 2nd gens also had the Control Trac system, but they had a separate relay for the Torque Control Solenoid. For the 3rd gen system, the TCS functions were integrated into the GEM, and the system now uses a separate wire to feed back from the clutch to the GEM instead of going straight to ground. It's that feedback wire we've been working on....

thammel said:

I started playing with my multimeter and separate clamp on ammeter attachment (which I've never used) to try and check the surrent flow in both the brown wire and the brown/yellow wire. I'm testing the darm clamp on device and not getting any reaction (using ac wires feeding lamps in my house). I'll keep working this one. Also, I re-read your last post re possibly using a SPDT switch. Wouldn't I want to use a DPST switch to turn off both B and B/Y wires? One option would be a DPDT switch where I put in a dummy load to simulate the transfer clutch solenoid in the "off" position. That occured to me today - that I could trick the system into thinking it is seeing the transfer solenoid (so it won't flash the 4x4 light!) when it is really not active. I'll keep working the problem - this weekend I'm not having as much time as I wanted to work on this issue.

Click to expand...

I could be wrong, but do those clamp-on meters even work for DC current? Your household wiring is a whole different beast, but I believe that most of those meters are supposed to go around only one leg of the AC circuit to get a reading... Never played with one myself though.

The DPDT switch is what I was working towards, but I needed to know the voltage drop across the clutch coil, as well as the amount of current the coil draws with that setup. I didn't want to suggest using a DPDT switch right off the bat and have you feed full power back into the GEM if it's only expecting a millivolt or two.... that could result in a nasty (not to mention WAAAAAY expensive) GEM melt-down. One step at a time, I guess.

I'd check it myself, but alas, I don't have a willing victim on this end LOL!!

-Joe

any updates on this project?