"no bus" after wiring swap

[Digger87xj]

Fuse 19 (20a) supplies power to the DLC, pin 16

The grounds, pins 4 and 5 for the DLC are at the dipstick attachment stud on the engine block.


Corrosion on the connectors for the instrument panel was/is a common issue. Typically not a difficult fix, but worst case scenario is replacing the connectors with a kit from jeep.

 

[spinaldex]

Turned the key to "on".

No power on Pin 16 on the DLC, but the fuse is good and I replaced it just in case.

I put the positive on my multimeter on pin 11 and the ground to the frame and saw just above 2 volts. However, I don't get anything when connecting the ground on the multimeter to ports 4 or 5.

Does that mean I'm neither getting power *not* ground to the DLC?

 

[Digger87xj]

I failed to mention.. fuse 19 is in the PDC under the hood. also, the key does not need to be turned on.

Does that mean I'm neither getting power *not* ground to the DLC?

I can't quite get your syntax but, if I understand correctly you are not getting power, and it seems there is no ground, though terminals 11 and 3 are the communication bus wires for PCM, and not really a not a good source of voltage to check your ground terminals.

did you make sure the ground wires at the dipstick are attached?

 

[spinaldex]

Oops, I had a typo there.

Basically, regardless if the key is on or off, I can't use pins 4 or 5 on the DLC to get a ground, nor does pin 16 have power. The only one I noticed had any power was #11.

I misunderstood so I replaced fuse #19 on the interior fuse panel.

Quick question on #19 in the PDC, looking at this diagram, are you talking about the "auto shutdown relay" marked F19 in the picture below?

 

[spinaldex]

Btw, replacing F19 displayed above didn't have an effect.

 

[spinaldex]

Ok, so the DLC doesn't have power. And you say it gets power from Fuse 19, right? So I should be able to run my multimeter on Fuse 19 and verify it has power. If it does, what is between #19 and the DLC that could be interrupted? Does it route through the fuse panel on the passenger side? Or, does it go through the main harness in to the cab on that huge white block that screws in under the driver's side dash?

 

[spinaldex]

I read in a few other posts (here for example: http://www.cherokeeforum.com/f2/dlc-no-power-obd2-162775/ in Post #6), that its fuse #17 which is shared with the headlights. Headlights work and then I used the multimeter to verify that the fuse is good as well.

There has to be a break in the connection somewhere which is why I'm not getting power to #16 on the DLC.

I hear the circuit is tied in to the headlight switch. If there was anything wrong on the wiring harness to the headlights, could that do it?

 

[spinaldex]

I traced down all the wiring from the headlights and it all seems connected right, and again, the headlights work so I'm not sure.

Does the feed for the DLC run through the loom that wraps from the passenger side in front of the radiator and then past the PCM?

 

[spinaldex]

This is for a '98, but if I assume for a second that this is accurate ... am I reading this right that power to the DLC goes through the headlight switch? Is there some way I could have disconnected it or something on that path could have been interrupted? If so, do you have any suggestions?

Thanks!

 

[Sidewinder CC]

Have you reinstalled the 2000 wiring harness, including the PDC?

If so, and you are concerned about getting power to the DLC, look at the diagrams and pics below.

2000/2001 PDC:

DLC pin out/CCD Bus Modules (The schematic shows fuse F17 as power for DLC pin cav 16 - this is for '97-'99 XJ's; F19 is the fuse for 2000/2001):

2000/2001 fuse ID photo:

Location of DLC ground G102 (oil dipstick tube attach stud):

.
Fuse F19 in the PDC is power to pin cav 16 on the DLC.

First check to see is the DLC ground wire(s) is/are hooked up to G102. If you have ABS, there may be another ring terminal for G102.

Next, at the DLC, touch pin cav 16 with your meter + probe and pin cav 4 and then 5 with your meter probe - you should see 12 volts. If not, move your meter - probe to a good clean structure under the dash and try it again.

 

[Digger87xj]

This is for a '98, but if I assume for a second that this is accurate ... am I reading this right that power to the DLC goes through the headlight switch? Is there some way I could have disconnected it or something on that path could have been interrupted? If so, do you have any suggestions?

Thanks!

Just to reiterate, 98 diagrams are not the same as a 2000. Close, but far enough apart to cause you headache.

No, power does not go through the headlamp switch.
It shares power from fuse 19, and it depicts that the wire first leads to the headlamp switch and pigtails off to the DLC

 

[spinaldex]

Yes, I switched back to my old 2000 wiring, PCM, etc so its all back together the way the factory intended.

The fuses in the PDC are all working. I've used a fuse tester and touched my multimeter to the test spots on top of the fuses while in the PDC to make sure they are hot.

When I tested this about 100x yesterday, I was not getting any power to #16 on the DLC. So even though the fuse has power, its not making its way all the way to the DLC. So, if its routed through the headlight switch, could that be another place to check for loose connections, faulty connection, etc?

I also couldn't get a ground off #4/5. I've removed, cleaned and re-attached that ground on the dipstick about 5x so far. I even used a pair of jumper cables to jump that bolt over to the negative battery terminal.

Is it too much coincidence to have both the ground and power to the DLC out at the same time? Is there no plug/connection/etc they share in the vehicle?

 

[Sidewinder CC]

Yes, I switched back to my old 2000 wiring, PCM, etc so its all back together the way the factory intended.

The fuses in the PDC are all working. I've used a fuse tester and touched my multimeter to the test spots on top of the fuses while in the PDC to make sure they are hot.

When I tested this about 100x yesterday, I was not getting any power to #16 on the DLC. So even though the fuse has power, its not making its way all the way to the DLC. So, if its routed through the headlight switch, could that be another place to check for loose connections, faulty connection, etc?

I also couldn't get a ground off #4/5. I've removed, cleaned and re-attached that ground on the dipstick about 5x so far. I even used a pair of jumper cables to jump that bolt over to the negative battery terminal.

Is it too much coincidence to have both the ground and power to the DLC out at the same time? Is there no plug/connection/etc they share in the vehicle?

Try using an Ohmmeter from pin cavity 4 then 5 at the DLC to chassis ground and see if you have continuity to G102.

When checking for power at DLC Cav 16, did you try using the dash structure, or some other chassis structure, as the ground for your meter?

Digger87xj is right, the power wire from F19 tees off at the headlamp switch. That diagram is identical to the 2000 diagram except the 2000 diagram shows F19 instead of F17.

 

[Sidewinder CC]

Here's the 2000 headlamp switch pin out. You can see that there are two wires at pin 4 of the switch. One goes to the DLC.

 

[Digger87xj]

Is it too much coincidence to have both the ground and power to the DLC out at the same time? Is there no plug/connection/etc they share in the vehicle?

Reference your diagram.

both power and ground pass through connector C100. The dashed lines represent that they share that connector, the small letter/number combos next to each wire at the arrowheads are the pin numbers.

You may have some bent or backed out terminals in C100

 

[spinaldex]

Anyone have a link to a 2000 C100 diagram? I can't find one in my manual. I had to twist both sides of the C100 connectors (the part on the engine harness and the part coming from the cab) a bit so that sounds like a good idea. It wouldn't be on the engine harness side because I've tried two different harnesses so far and neither worked, so my assumption is its on the dash side of the connector at this point.

 

[spinaldex]

If these are the right ones (yay internet), then it looks like the following C100 pins are relevant:

A18 - DLC Power
A1 - DLC Pin 4 Ground
A7 - DLC Pin 5 Ground

If so, I should be able to disconnect the two haves of C100 and use my multimeter on these pins to verify power is at least getting to that point, right?

Then, if so, then I can test the dash side of the connector and keep going.

Does that sound like a reasonable next step?

 

[Sidewinder CC]

If these are the right ones (yay internet), then it looks like the following C100 pins are relevant:

A18 - DLC Power
A1 - DLC Pin 4 Ground
A7 - DLC Pin 5 Ground

If so, I should be able to disconnect the two haves of C100 and use my multimeter on these pins to verify power is at least getting to that point, right?

Then, if so, then I can test the dash side of the connector and keep going.

Does that sound like a reasonable next step?

I'm afraid you're barking up the wrong tree.

That C100 pin out is for a 1997 Right Hand Drive XJ.

Besides that, If you can turn on your headlamps and rotate the headlamp knob back and forth and you see your panel lights brighten and dim, there's nothing wrong with the power wire from fuse F19 in the PDC to pin 4 of the Headlamp switch connector.

The power wire to the DLC (pin cav 16) is connected to pin 4 of the headlamp switch. If you are getting power to the headlamp switch dimmer function power is getting through connector C100.

Did you ever do the checks I suggested in post #53?

It looks like you are struggling. I do recommend that you get a genuine 2000 XJ Cherokee factory service manual. It will have all the wiring diagrams, connector pin outs, etc., and that you get a quality manual ranging digital multimeter.

 

[spinaldex]

First, let me thank everyone for all their help. I'm trying to pick this up as quickly as possible and I've been reading where I can on how to use multimeters and picking through the factory service manual I now have in my possession.

Ok so a few updates:

0. I found the right LHD 4.0 wiring diagram from the factory service manual and pulled the relevant pins for things used below from there.
1. I checked continuity between the DLC Ground (G102) and pins 4/5 on the DLC and there's none.
2. I checked continuity on the C100 - E7 and G102 and had continuity.
3. I checked continuity on the C100 - A1 and did not have continuity.
4. I checked for power on C100 - E6 and had power.
5. I checked for power on DLC Pin 16 and had no power.
6. I can turn on the headlights using the headlamp switch.
7. I cannot turn the headlamp knob to see panel lights brighten/dim. They are off no matter what.
8. I checked that both ring ends connected to G102 have continuity to every other ground connection (strap, the ones on the fender well near the PCM, etc).
9. I looked at the opposite end of the C100 plug that comes from under the dash and the wires and pins look healthy. I don't see any reason there should be an interruption in the ground reaching pins 4/5.

So, at this point, unless I read the FSM diagram incorrectly, there's some kind of disconnect on the grounds reaching the DLC, as well as power making it from the C100 plug through the headlamp switch and then to the DLC.

My next step was to do a continuity check from the inside C100 half of the plug to DLC 4/5 to see if there's something going on with the wiring, like maybe something ripped/burned through (who knows). I was also going to figure out how to get the plug off the headlamp switch to do the same thing there.

 

[Digger87xj]

well, sounds like the problem is at C100 to me.

I suspect something got bent, or a terminal pushed out of the body side of C100 when you installed the 98 harness to it.