My 1999 Dakota RT Recently had the horn stop working. It will not work via the wheel or the panic and lock button on the Fob. I have checked and confirmed that the horn itself works via direct 12v to the horn itself, and jumping the relay in the engine fuse panel. I have swapped relays, confirmed the fuse is ok and the horn button works. I suppose the issue is between the horn button and the fuse panel relay? I am unsure what to check at the panel to confirm the relay is being triggered. ( I assume its the same circuit in panic mode and horn button)
I should start with asking if anyone has a schematic of the horn circuit or know of something i may have missed?

Thank you and I hope you and yours are safe in these crazy times.

This is how the Dakota currently looks

 

Now that is a cool looking Dakota.

Probably going to be something in the control circuit for the relay. Verify you have power at the correct pins, or ground, as the case may be. Don't know if the button controls power, or ground for the horn.

 

Based on the data I have, if the horn relay fails to actuate by both wheel and CTM, then I would check the horn fuse, followed by the relay socket or the joint where the CTM and wheel come together.


The high-line CTM also controls and integrates many of the additional electronic functions and fea- tures included on models with this option. The horn relay is one of the hard wired outputs of the CTM. The high-line CTM is programmed to energize or de- energize the horn relay in response to certain inputs from the Remote Keyless Entry (RKE) system and/or the Vehicle Theft Security System (VTSS).

When the center area of the driver side airbag trim

cover is depressed, the electrically conductive grids on the facing surfaces of the horn switch membranes contact each other, closing the switch circuit. The completed horn switch circuit provides a ground for the control coil side of the horn relay, which activates the relay. When the horn switch is released, the resistive tension of the convex membrane separates the two electrically conductive grids and opens the switch circuit.

https://photos.app.goo.gl/3hC9EQx3L7CA7tUG7

https://photos.app.goo.gl/roqsN8rSbzeMQ2ay8

 

(5) Check for continuity between the steering column half of the horn switch feed wire harness connector and the horn relay control circuit cavity for
the horn relay in the JB. There should be continuity.
If OK, go to Step 6. If not OK, repair the open horn
relay control circuit to the horn relay in the JB as required.

I've been following a quite good service manual for the Dakota and after checking through alot of the systems, the above is where I've gotten to. When I was checking continuity to the Horn relay control circuit cavity I just checked every connector of the relay at the JB because I don't know which connection its referring to ( I see Now Mr McDermott posted above I was looking for '85') Thank you for that Schematic! . I DO NOT have continuity at any of those points, So, I suppose my issue is in fact between the wheel and the passenger JB.
I have to assume its in the clockspring? does this indicate that? I wish I could determine the correct wire after the clockspring to the JB and check for continuity.

 

yes and no.

In both schematics, see where there is an arrow between pin 85 on the relay and the border for the JB? Those arrows point to eachother.

Both the clockspring AND the CTM ground the horn relay to engage the relay. Because neither causes the horn to operate, I am thinking your issue may exist between that splice and the relay pin itself. If you want to test this, pull the relay out and place a voltage measuring device between the 2 coil wires on the relay (85 and 86). When you lock using the RKE or bonk the horn button, you should see 12 volts across those 2 contacts.

If you don't, and I bet money that you don't given your previous troubleshooting, verify 12 volts at pin 86 relative to a known good ground. That make sure it's a ground-side fault.

Now the next part is tricky. Locate the CTM. I think in the 99 it's to the right of the glovebox. The wire you are looking for per my 2001 book is connector 1, pin 5 - black and red. Again per my 2001 book, it's the gray connector, and with the female pins facing you and tab up, it is #5 from the left on the top row (layout is 1-13, 14-26). Your 99 will probably differ in placement but not wire color (thank you dodge for keeping most wire colors the same despite the 9,000 revisions of the electrical system). Backprobe that wire, lock with the RKE, see if you get a ground signal (using ohms to ground or volts from a good 12V).

Less tricky but equally aggravating, find the black and red wire coming out of the steering column. There's a bundle of about 15-20 wire there and slack doesn't exist. Probe it, bonk the horn, verify a ground signal exists.

 

If you want to test this, pull the relay out and place a voltage measuring device between the 2 coil wires on the relay (85 and 86). When you lock using the RKE or bonk the horn button, you should see 12 volts across those 2 contacts.
No voltage across 85 & 86 when depressing the horn button.

If you don't, and I bet money that you don't given your previous troubleshooting, verify 12 volts at pin 86 relative to a known good ground. That make sure it's a ground-side fault.
12v at pin 86.

Less tricky but equally aggravating, find the black and red wire coming out of the steering column. There's a bundle of about 15-20 wire there and slack doesn't exist. Probe it, bonk the horn, verify a ground signal exists.
With Meter in auto ohms, lead to ground, lead probing the black and red wire traced back to the clock spring, depressing horn button gives me 52 or so ohms, So that should verify a good signal.

Now the next part is tricky. Locate the CTM. I think in the 99 it's to the right of the glovebox. The wire you are looking for per my 2001 book is connector 1, pin 5 - black and red. Again per my 2001 book, it's the gray connector, and with the female pins facing you and tab up, it is #5 from the left on the top row (layout is 1-13, 14-26). Your 99 will probably differ in placement but not wire color (thank you dodge for keeping most wire colors the same despite the 9,000 revisions of the electrical system). Backprobe that wire, lock with the RKE, see if you get a ground signal (using ohms to ground or volts from a good 12V).

So this one is not so bad for access, but I'm unsure of placement. Pictured is the only black and red wire on this connector, I used the same ground as above, probed the pin on the connector (wiring side not CTM) and locked with the fob. Nothing at all.

 

Yep that's definitely the horn trigger wire.

52 ohms is about right. CTM makes me go hmmm, but the horn button should at least work.

But that definitely tells us there is a wire break going to the socket. I've never opened a PDC to know what is inside....

 

Which socket are we talking about? the one for the relay in the PDC? if I can narrow down the rough physical area there is a wire break i can at least search for it. Is there a way I can make a work around and install a patch wire to bypass the issue?

 

If you can artificially find a way to trigger the ground side of the relay, that should fire the horn enough to pass inspection.

You could even tie it to that red/black wire at the column and see if it'll make the button work.

 

So to be clear, the likely break is between the ctm and the pdc?