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2009 STS & 2015 XRS
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Discussion Starter #1
New questions for some of you more technical gurus on this site. My heated wheel fails to turn on like many others have in this forum (no light on switch and no heat when depressed) on my 2009 STS. I've read, re-read, scoured through AllDataDYI and still can't find the answers to my questions. I've pulled apart the steering wheel and tested as much as I could, given the information from all my sources. To the best I can discern, the heated Wheel control module is bad. It has power to the module, but nothing coming out on any wire. I've also Ohmed out the actual heater element and temp sensors, neither of which are "open". My questions are:
1. Anybody have the wiring diagram for the Heated Wheel control Module? I can't seem to locate in AllData.
2. Anybody have the ohms specifications for the wheel element and temp sensor? Again, can't locate in AllData.

Thank you for any help you can provide!

EB
 

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2015 SRX LUX 2014 CTS LUX Phantom Grey (previously 2008 STS)
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1,703 Posts
New questions for some of you more technical gurus on this site. My heated wheel fails to turn on like many others have in this forum (no light on switch and no heat when depressed) on my 2009 STS. I've read, re-read, scoured through AllDataDYI and still can't find the answers to my questions. I've pulled apart the steering wheel and tested as much as I could, given the information from all my sources. To the best I can discern, the heated Wheel control module is bad. It has power to the module, but nothing coming out on any wire. I've also Ohmed out the actual heater element and temp sensors, neither of which are "open". My questions are:
1. Anybody have the wiring diagram for the Heated Wheel control Module? I can't seem to locate in AllData.
2. Anybody have the ohms specifications for the wheel element and temp sensor? Again, can't locate in AllData.

Thank you for any help you can provide!

EB
Very common issue. Failed heating element in wheel. Only fix is to replace the wheel which will be very very difficult because they are HARD to get
 

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2009 STS & 2015 XRS
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Discussion Starter #3
Very common issue. Failed heating element in wheel. Only fix is to replace the wheel which will be very very difficult because they are HARD to get
That's what some say. However the Heated Wheel control module is a seperate item (still available) and cost is way less than a wheel. In addition, I do not know if the wheel comes with module and switches. I'm still looking for specific answers to my questions.
 

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08 STS-4 N* 1SG, 08 DTS Luxury II, 04 Bonneville GXP N*
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The replacement steering wheel (at least 2008+) comes with the steering wheel controls with bezels, heater control module and the plastic trim on the back of the wheel assembly. There also doesn't seem to be nearly as many problems with these as the 2005-07 wheels. I replaced mine, but only because it was fully leather wrapped. One of my friends finally pressured me into installing the version with the wood across the top. Some nonsense about "it's not really a Cadillac unless there is wood on the steering wheel".

Personally, I very much dislike AllDataDIY. I find it is poorly organized and difficult to navigate. I'm not surprised you aren't finding what you're looking for.

The control module has three connectors (X1, X2 and X3). I know with AllDataDIY you'll have much of this information, but for the benefit of other readers that may not, I've posted it. You'll may find some of the info you're looking for toward the bottom.

Connector X1 has four cavities:
A - Yellow Wire, Steering Wheel Heating Element Supply Voltage
B - Yellow Wire, Steering Wheel Temperature Sensor Signal
C - Red Wire/Black Stripe, Ground
D - Red Wire/Black Stripe, Ground

Connector X2 has two cavities (with MALE terminals, female housing):
A - Orange Wire, Indicator Control
B - Yellow Wire, Heated Steering Wheel Switch Supply Voltage

Connector X3 has two cavities (with FEMALE terminals, male housing):
A - Red Wire, Ignition 3 Voltage
B - Black Wire, Ground

In exceedingly small text, you should be able to see some markings embossed on the connector housings to determine which cavity is which.

The heating element is connected to X1 terminals A and D. If I read the documentation correctly, you're looking for 1.5 - 3.0 ohms. I can measure my original wheel and see what it is, but this won't be for a couple of days.

There is no (internal) wiring diagram for the module itself as a technician would never repair it. If it's defective. I'm sure GM has it, but you'll never get it from them.

What colour is yours?
 

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2009 STS & 2015 XRS
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Discussion Starter #5
Thanks for the info ddalder. That is the same info I got out of AllData, except for the resistance readings. I am questioning the validity of the info in AllData, only because when I measure across both yellow wires I get about 20 ohms, and I measure across both red/blk I get about 20K ohms. If I go by the book and measure yellow to red, they are "open", which does not make sense since both the others have a connection and read.
I will be traveling the next few days. I would really appreciate it if you could check your wheel and report back. My wheel color is light tan w/wood on top (wish it was all leather).

Yes, I know I could just bite the bullet and by the wheel assembly, but I'd really like to know vs. expensive shot-gunning.

Thank you for the help!
 

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08 STS-4 N* 1SG, 08 DTS Luxury II, 04 Bonneville GXP N*
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Okay, I'm not sure exactly what the deal is, but the technical info is clearly incorrect. The wire colours in the schematics and connector end views are only partially correct. They make reference to colours that simply don't exist when looking at the actual steering wheel wiring harness.

Anyway, long story short, it appears that the two YELLOW wires are the heating element (contrary to the documentation). These wires are in connector cavities A & B and I measure 2.5 ohms. The temperature sensing is accomplished through the two RED/BLACK wires in cavities C & D of the connector. This measurement has varied. When I first brought the steering wheel into the house, it measured 12K ohms. As it started to warm up, I measured about 10K ohms. Since this circuit uses a negative temperature cooefficient thermistor, it is perfectly logical that the resistance decreased as the wheel warmed up.

I have a few STS steering wheels, but the one I tested was the original that came installed in the car (and I know it works). The only reason I changed it (as mentioned), was to have the wood section at the top (thanks to pressure from Ludacrisvp). I opened the control module case to have a look since the heated steering wheel schematic GM published just doesn't match. I noticed a fractured solder connection on the main connector used to interface the circuit board with the heater, thermistor, power, ground, switch and indicator. It must not be completely broken (because as I said, the heater works just fine). You may want to check the solder connections on yours. I suspect that mine would have eventually opened and failed. The poor connection is in the thermistor circuit which of course would be one fault resulting in the module turning off. I've highlighted the fracture in the connection with an arrow (below).

The reason I asked about the colour was that I have an extra wheel I purchased as GM surplus. It's definitely not your colour though.

 

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08 STS4 V8 1SG & 04 SRX4 V8 & 01 Monte SS
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I replaced mine, but only because it was fully leather wrapped. One of my friends finally pressured me into installing the version with the wood across the top. Some nonsense about "it's not really a Cadillac unless there is wood on the steering wheel".
hmm I wonder who might have done this ... also it’s the wheel your car should have shipped with.
 

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2009 STS & 2015 XRS
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Discussion Starter #9
Thank you for the information ddalder. Sorry for the late response but I was away traveling.
Like I originally posted, the technical info I found did not make sense either. What you are reporting about the wire colors and resistance values sounds about right. The reality is that the heating element in the wheel is not broken. It seems to be more of a module problem to me. According to OEM-GMparts website, the module is available (15908070) for $168. This is a lot less expensive than buying the whole wheel assembly. But can be a gamble if the module cannot really be tested accurately.

I can understand buying a new wheel if necessary, I just want to make sure it is necessary.

Does anybody have any more detailed info on the Heat module? There are 2 wires coming from the module to the Heated wheel switch. Should one have power, or does it get power from one of the other wires in the multipack switch connector? All the other controls in that left switch assembly respond correctly.
 

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The switch works in a very typical manner of most that control electronics. One side is connected to ground, and the other to an input on the module. The module will have a pull-up resistor that will always keep the input at about 5V. When you press the switch, it will short the input to ground causing the input to drop to 0V. The reason for this is to eliminate a "floating input" on the module. This can cause erroneous behaviour and may cause the input to trigger on or off unexpectedly. With a pull-up resistor, the input will always be 5VDC or 0VDC, never in between. If you measure from the switch to ground (see below) you should see about 5VDC and when you press the heater control button, it will drop to 0VDC as long as you are holding the button down.

There will be two yellow wires on the left steering wheel switch connector. One in cavity 3, the other on the end which is cavity 8. You want to make your measurement on the yellow wire in cavity 8. Cavity 3 is for the switch backlighting.
 

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I tested my STS 05-07 style wheel that I put in the 04 SRX by just running +12v into the heating element directly.
It worked so I then did the efforts of making the wheel able to be used in the SRX making it one of very few with OEM heated wheel for the 1st gen.
This method of testing also proved the wife’s 2011 sonata wheel heater was good and the fault was with the controller board.
 
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