2000 Bonneville Horn Inoperative

[peter]

I'm having an issue with the horns not working. I've confirmed the horns themselves work as I jumped the 12v fuse pin to the relay pin to enable the horns so physically they are capable of working. (also jumped from relay 12v power to the horn as a secondary test) I've also tested the relay by jumping 12v power to it to make sure power can get across and that's working fine.

I believe my only other suspect issue would be the horn contacts under the horn pad -- anyone have a schematic of the steering column wiring so I can just test it there before I take the horn pad off? I've been trying to take the horn pad off with tiny screw drivers and picks and have been having a hell of a time. For those that have done this, have you just sprung (no pun intended) for the J-44298 tool? Any info would be helpful

Thanks

[ddalder]

If it is in fact the switch contact, you're really looking at replacing the air bag. This is all a single assembly and if you start to take it apart, you'll compromise the integrity of the SIR system. I have removed the air bag with small screwdrivers, but this isn't ideal and I simply purchased the tool.

The horns in these can be a little temperamental. I find that with mine, the horn must be pressed in just the right spot or it won't activate.

What you can try is a jumper at the connector under the dash where the steering column harness plugs into the main body wiring harness. This will certainly confirm if the problem is in the steering column, or somewhere else. I'll post the information you'll need as soon as I can.

[ddalder]

If you remove the knee bolster under the steering column (pull rearward toward the driver's seat), you'll find two large 40-pin connectors under the steering column. To easily access them, you 'MAY' need to remove the metal plate/framework which is held in place by four 10mm bolts. One connector will be BLACK, the other is WHITE. Each will have four rows of terminals. If you look very closely, you'll see a letters and numbers embossed in the plastic. On one side you'll see A1 at one end and A8 at the other. On the other side of the housing you'll see D1 and D8. The two outside rows are "A" and "D" while the two inside rows in between are "B" and "C" (in normally progressing sequence). Rows A & D each have 8 cavities while rows B & C each have 12.

You are looking for a BLACK wire in cavity B12. This will be on one end of the connector, second row in. Carefully insert a jumper into the cavity to make contact with the terminal (you should be able to do this without disconnecting the two halves) and touch the other end of the wire to ground.

If the horn sounds, the problem is either with the switch contacts inside the airbag, horn brush contact in the steering column (horn uses a separate mechanical contact in these cars and doesn't go through the clockspring), or the steering column wiring harness.

This is a photo of the connectors (ignore the big yellow arrow, this photo was originally posted for another thread).

[peter]

great information dalder -- much appreciated. I'll test this out either tomorrow or one of the following weekends and provide an update.

Correct me if I'm wrong but I suspect the horn contacts at the airbag are more susceptible to this kind of failure? The car has only 70k on it so I'm frankly surprised either is an issue

[ddalder]

To be honest, I don't recall ever seeing a lot of horn problems related to the contacts in the airbag assembly. I may have missed some over the years, but yours would actually be the first (I'm aware of). Most often I'd say it's the horns themselves affected by road contamination, corrosion or bad wiring contacts. I know that I've had to replace mine twice now for one of the two failing. I only have 125,000km which is about 77,600 miles. I think there's been the odd relay as well and perhaps one instance of chaffed wiring in the column (although this is more likely to short and cause the horn to sound unexpectedly).

I look forward to your update.

FWIW, there are no other connectors in between the 40-Cavity one located in the dash and where the main body wiring harness plugs into the bottom of the under hood fuse block making it unlikely that the problem is between those two points.

[peter]

Providing a small update on this. Dug into this some yesterday and found I don't have continuity between the black wire in cavity B12 and the front fuse block. I unwrapped this harness under the driver's side dash and in the engine bay; the harness goes into the passenger side firewall and appears to run along the middle backside of the dash. :(

This car had a mouse problem at some point as I found their evidence in misplaced insulation (and a receipt for a blower motor) in the past; I have no idea what the chances of them chewing through a single wire as I have yet to come by any other system(s) malfunctioning. Perhaps the mouse had nothing to do with it and it's just a pinched or fatigued wire, I'm really not sure

Because of the way the harness is routed it appears my only shot of fixing this the "right" way would be removing the dash and I admit I really do not want to do that. As of right now my method of choice is leaning towards routing a new wire from the front fuse block to my column wiring harness connector and calling it done.

[ddalder]

What happens when you set off your alarm intentionally? Does the horn sound?

What is interesting is that according to the schematic, the wiring from the horn switch passes through the body grommet P100 which is on the left side of the car under the dash. There is a separate wire from the Dash Integration Module (DIM) that can also activate the horns (which is how the alarm system would do this). The DIM is on the right side of the dash behind the glove box. The wire from that passes through body grommet P102 which is on the passenger side of the car to the right of some HVAC components. In each case, the two wires join at the under hood fuse block.

Now, if the alarm system successfully sounds the horn, a temporary fix would be to run a new wire across the dash to behind the glove box and connect it to the wiring plugged into the DIM. The horn control from from the DIM is also a black wire. It connects into cavity A6 of connector C3. Connector C3 is gray in colour and has 24 cavities. There are no other gray connectors plugged into the DIM.

The routing from the horn switch into the engine compartment on the left side seems odd. This doesn't sound right to me based on when I replaced my main body wiring harness. Mine is a 2004 so it may be a little different, but just based on how the wiring passes through the body, if it exits as the schematic suggests, it would need to pass through at least one other connector in the engine compartment to meet up at the fuse block. The schematic does not show that it does.

[peter]

Ok that is more good information. I do not have a working key fob right now so that doesn't help my diagnosis. (which is a little thing that hurts).

I'm going to have to peel back the wiring a little better under the drivers side of the dash to follow it as ideally I'd like to put together a professional fix and avoid cutting corners. Hoping to get back at it this weekend

If worst comes to worst; it sounds like it'd be a nifty fix to splice into the horn wiring at the DIM like you mentioned

[ddalder]

You don't need a working fob. Roll down your window, lock the door and close it. Open the door by reaching in and pulling the interior handle. When the alarm goes off, you should be able to disarm it either by starting the car with the key, or unlocking the driver's door with the key.

If the horn sounds, we at least know the wiring is intact between the DIM and the horn relay.

[96 SSEi]

You don't need a working fob. Roll down your window, lock the door and close it. Open the door by reaching in and pulling the interior handle. When the alarm goes off, you should be able to disarm it either by starting the car with the key, or unlocking the driver's door with the key.

If the horn sounds, we at least know the wiring is intact between the DIM and the horn relay.

YES, JUST ONE THING TO ADD TO ABOVE, you must wait at least 5 min between locking and closing the door and reaching through window to open or it wont arm and you waste time.

[peter]

thanks guys for the help here.

I went the route of splicing the column horn wire to the same harness as the dash module so I now have a working horn!

[ddalder]

That's very good news!

I'm still a little confused about the wire routing. The picture below is the main body wiring harness that I custom modified and installed in my car. The factory schematic shows that the horn wire exits the passenger compartment in the branch circled in yellow which is on the driver's side. In order for this to be the case, it would need to run through the engine harness which ultimately plugs into the bottom of the fuse block. The schematic however doesn't show the wire passing through that large black connector in that branch which mates with the engine harness.

The branch circled in white exits the vehicle on the passenger side. The large gray rectangular connector plugs into the bottom of the fuse block. It's this routing that is used for the wire from the Dash Integration Module. Fair enough, that part all makes sense. I "suspect" the wire from the steering wheel horn switch runs through the instrument panel harness, across the dash and out to the fuse block through the right side as well. Problem is, this also isn't what the schematic shows. My conclusion is that the schematics are incorrect. This, and other inaccuracies in the service manual happen from time to time.

The other part to this is that for the 2000-01 model years, your instrument panel harness is actually a flexible printed circuit and not traditional wires. If the problem is in the instrument panel harness, it's likely because this flexible printed circuit is damaged (perhaps it rubbed on something until the conductive trace for the circuit in question opened up). These are not easily repairable and generally a pain to work on because to replace them, you need to remove the dash from the car.

In any event, it's great to hear that you have a working horn now! Congrats on successfully completing the repair.

[3800wrench]

I just bought my bonneville and have been solving numerous electrical problems. One of them is still the horn does not function when pressing the steering wheel, however if I set off the panic alarm it will sound the horn. Today I followed the instructions provided by ddalder for jumperimg the connector under the dash. This test was successful, when I attached the jumper the horn sounded. After this I am led to believe the horn/airbag assembly is bad. Any opinions?