Horn ground

[ikeG]

Where does the 03 - 07 trucks get the ground for the steering wheel? In order for the horn to work on an 06 I have in, I have to ground the steering wheel(the actual cast structure of the steering wheel), and then the contacts work fine and horn functions.

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[2004LB7]

I'm pretty sure it grounds through the steering shaft

Electrical diagram says "case horn" and "case column". I'm guessing that means ground the horn to the case. But as far as I remember. There is only one wire running up for the horn contacts

 

[ikeG]

With airbag installed, I literally have to smash it, in an upward motion to get horn to work. But if I ground the steering wheel structure, the contacts work as they should, with hardly any pressure applied. Kinda throwing me for a loop

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[2004LB7]

You might want to poke your head in the wheel well and inspect the shaft. Might be a loose bolt or corrosion. If you pull or push the steering wheel to put pressure on the shaft, does it work any better?

 

[ikeG]

I'll dig in a little further tomorrow. It's a pretty rusty PA truck. Will be interested to see what this could be. Thanks

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[2004LB7]

Might need to attach a ground to the shaft with enough slack to accommodate the rotation if it's that bad

 

[ikeG]

Grounding the intermediate shaft makes no difference. I literally have to apply my own ground to the steering wheel structure or right to the shaft (at the steering wheel nut) for horn contacts to function normal

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[Cougar281]

Bad clockspring?

 

[ikeG]

Ok, if I heave hard in any direction on the steering wheel, it makes ground and horn functions correctly. Meter shows continuity from shaft to ground when I heave on wheel but none when I let go. Does the shaft get grounded thru mounts to body and steering box/chassis or does the clockspring provide ground?

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[1FastBrick]

I thought it ran through the Clock spring as I believe that's what you plug it into.

 

[1FastBrick]

Horns Inoperative​

Test Description​

The numbers below refer to the step numbers on the diagnostic table.

1. Verifies that the body control module (BCM) is providing ground to the horn relay.

1. Tests for voltage at the battery positive voltage terminal of the horn relay coil.

1. Tests for voltage at the battery positive voltage terminal of the horn relay switch. The HORN fuse supplies power to the battery positive voltage terminal of the horn relay switch.

1. The horns need maximum current flow to operate properly. A high resistance, greater than 0.5 Ω, in the horn control circuit or the horn ground circuit could cause operating problems with the horns. Inspect the circuits for faults that would restrict current flow.

1. The horn relay control circuit includes the horn switch. The horn switch must be tested for a high resistance, an open or a short to voltage when testing the relay control circuit.

Step​	Action​	Yes​	No​
1​	Did you perform the Diagnostic System Check – Vehicle?​	Go to Step 2​	Go to Diagnostic System Check - Vehicle​
2​	Depress the horn switch. Do the horns operate?​	Go to Step 3​	Go to Step 5​
3​	Install a scan tool. Turn ON the ignition, with the engine OFF. With a scan tool, command the body control module (BCM) horn output ON and OFF. Do the horns operate?​	Go to Testing for Intermittent Conditions and Poor Connections​	Go to Step 4​
4​	Test the BCM portion of the horn relay control circuit for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition?​	Go to Step 21​	Go to Step 11​
5​	Turn OFF the ignition. Disconnect the horn relay. Connect a test lamp between the battery positive voltage circuit of the horn relay coil and a good ground. Does the test lamp illuminate?​	Go to Step 6​	Go to Step 14​
6​	Connect a test lamp between the battery positive voltage circuit of the horn relay coil and the horn relay control circuit. Depress and hold the horn switch. Does the test lamp illuminate?​	Go to Step 7​	Go to Step 15​
7​	Connect a test lamp between the battery positive voltage circuit of the horn relay switch and a good ground. Does the test lamp illuminate?​	Go to Step 8​	Go to Step 16​
8​	Momentarily connect a 15-amp fused jumper wire between the battery positive voltage circuit of the horn relay switch and the horn control circuit. Do the horns operate?​	Go to Step 12​	Go to Step 9​
9​	Reconnect the horn relay. Disconnect either horn connector. Connect a test lamp between the horn control circuit and a good ground. Depress and hold the horn switch. Does the test lamp illuminate?​	Go to Step 10​	Go to Step 17​
10​	Connect a test lamp between the horn control circuit and the horn ground circuit. Depress and hold the horn switch. Does the test lamp illuminate?​	Go to Step 13​	Go to Step 18​
11​	Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct the condition?​	Go to Step 21​	Go to Step 19​
12​	Inspect for poor connections at the horn relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct the condition?​	Go to Step 21​	Go to Step 20​
13​	Repair the high resistance in the horn control circuit or the horn ground circuit. Also, though unlikely, it is possible that both horns are defective. Refer to Circuit Testing and Wiring Repairs. Did you complete the repair?​	Go to Step 21​	—​
14​	Repair the open or high resistance in the battery positive voltage circuit of the horn relay coil. Refer to Circuit Testing and Wiring Repairs. Did you complete the repair?​	Go to Step 21​	—​
15​	Repair the open or short to voltage in the horn relay control circuit. The horn relay control circuit includes the horn switch. Refer to Circuit Testing and Wiring Repairs. Did you complete the repair?​	Go to Step 21​	—​
16​	Repair the open or high resistance in the battery positive voltage circuit of the horn relay switch. Refer to Circuit Testing and Wiring Repairs. Did you complete the repair?​	Go to Step 21​	—​
17​	Repair the open or high resistance in the horn control circuit. Refer to Circuit Testing and Wiring Repairs. Did you complete the repair?​	Go to Step 21​	—​
18​	Repair the open or high resistance in the horn ground circuit. Refer to Circuit Testing and Wiring Repairs. Did you complete the repair?​	Go to Step 21​	—​
19​	Replace the BCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?​	Go to Step 21​	—​
20​	Replace the horn relay. Did you complete the replacement?​	Go to Step 21​	—​
21​	Operate the horns. Do the horns operate properly?​	System OK​	Go to Step 1​

 

[1FastBrick]

Horn Schematics​

 

[2004LB7]

I don't believe the clockspring pass the ground. As Brick posted in the schematic, the circuit passes through the turn signal cancel cam then to ground. But it doesn't show the ground going through a cam or clockspring

I did find this on another forum

"there's a ground pin on the turn stalk assembly in the steering column. The pin is spring-loaded, and presses against a metal strip on the back of the steering wheel. If you clean off the lube from the pin/metal strip, the pin will wear out and then you have to replace the turn signal assembly to get it working again."

Might be referencing that same cancel cam. If so then he would be mistaken as it provides the 12v and not ground. But if there is a second one that does ground then it would explain it

 

[1FastBrick]

Yeah the C201 is the connector on the column wire harness that connects to the dash harness. Been a while since I had one apart. Of course I probably have 3 or 4 of them kicking around.

 

[ikeG]

Theres only 1 pin on the multi function switch. It contacts the backside of the cancel cam. The horn contacts plunger contacts the cam on the front side. Everything functions as it should, except the steering shaft and wheel are not grounded enough to apply ground to the horn relay control circuit.
I ended up splicing into the ground circuit for the dic buttons and grounded the steering wheel structure. Done deal. Would have been nice to figure out where the shaft gets grounded.

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[2004LB7]

After looking at some diagrams. I think the upper steering bearing is used to pass ground. There is what they are calling a spring seat that passes the spring pressure onto the inner bearing race. I think this is the location where current is supposed to pass

I found one post in another forum, different vehicle but still GM. Had same issue as you. Ended up pulling the steering wheel to access the bearing. Removed the inner and outer race, cleaned all the old grease out of and put new grease in. Measured resistance and was 1 ohm afterwards and ground restored