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.

 

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?

 

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.

 

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!

 

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.

 

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.

 

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.

 

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.

 

Thank you guys for the help. I will test and let you know.

 

Thought I would update this thread with the final outcome. I ended up replacing the Wheel assembly (20857832, N31 option) with a used wheel assembly. All works now so we're good to go.
I tried several things including Ohming the heated leads, I could not find specs for it and nobody really could either. It seemed to be a crap-shoot. Switches tested good, I attempted to try a new Control Module (no avail) so in the end it was a complete replacement. GM's info on wiring and testing is just non-existent, and what is available has errors.

So while I was quoted $1000 wheel assembly part cost by the dealership, on-line searching brought the cost to $550 to $650. Still too rich for my blood, so I bought a whole used steering column (with wheel) for $160. Swapped wheels and works great. End of story and frustration .

 

Cool! By any chance did you wring out and compare the differences between your wheel that didn't heat to the replacement that does?

 

No, unfortunately I did not measure the "new" used wheel. All I wanted to do was to try it so I slapped it on (completely untested) and it worked fine.

 

I have been fighting the above problem on a 2008 SRX. I replaced the control module with same result ( no heat, no light ). So my thermal sensor is running at 12K ohms at 70F and my heating element is running at 9 ohms. Powering it directly produces heat in the wheel, perhaps a bit less than it was new but still nice and warm. So I started reverse engineering that control module 15908070 made by a company called WET systems. I have discovered the module is designed to operate around a very tight heating element resistance tolerance of no more than about 3 ohms and no less than about 1 ohm. The driver chip in the module feeds back current load to the control chip upon powerup ( which may only last a few milliseconds if incorrect current is sensed ), if the current is out of tolerance the control chip will refuse to latch in an ON condition. That is what most of you are experiencing as the car ages for some reason the heating element resistance increases to the point where the module no longer will allow it to turn on ( happens in electric blankets also). To fix this you can get a new steering wheel with a <3 ohm heater. Or you can change the bias of the control circuit to accept a 9 ohm heater. Now the difference is a 3 ohm heater will yield over 50 watts of heat, but a 9 ohm heater will only yield about 13 watts of heat. Still better than a cold wheel. So if you are interested in making this modification to your control module you can make it work again and have warm hands without replacing your wheel. I have attached information to add a 10K resistor to increase bias on the current sense feedback circuit. It is a simple mod ( if you can solder in tiny places ) and preserves all the other safeguards built into the module and restores operation as normal. Hope you can make use of this. This is a 2008 SRX but I would think similar issues with other Cadillacs of same vintage. I also attached a wiring diagram which I had to correct as the manual does have wrong information about color codes and pin numbers. GM troubleshooting on this subject is mostly useless. If you want more info on how to setup a bench test for the module, and you have some electronics experience, let me know.

UPDATE 2022
While this worked for a couple years, the root cause of the problem is the element in the steering wheel ends up going fully open circuit ( burns out ). So really the steering wheel replacement would be the ultimate and expensive fix. I decided I really did not need a heated wheel in our climate. Maybe repurpose the control module but don't know for what yet. There is heat tape you could wrap around the outside wheel but it would look ugly. Ugly not good on Cadillac!

 

I changed mine out as well, although I may have messed up the clock spring while doing so LoL. I'm under the impression that the heating element in the full leather wheels last longer than in the wood grain style wheels. Not sure where I got that idea, if someone said that previously or if I'm just making it up.

 

Hell yeah that's the way to do it! Get a new column and swap the wheel. Fortunately, mine still works and it has the wood grain top part on the wheel. Couple days ago, I got in the car, fired up the heated seat and steering wheel, drove a mile or so and put my left elbow down on a cold arm rest. Why don't these cars have heated door arm rests lol. Wonder if a Rolls Royce does.

 

I hear the newer ones have heated trunk lids, for pushing them in winter

 

I would of GLADLY swapped out my existing :wood-on-top" wheel for a full leather one. I could not find one that was full leather all the way around. My wife's SRX has full leather and is much nicer because the whole wheel is heated. This 1/3 unheated "wood-on-top"wheel is bull_hit.

 

J&MR;
EXTREMELY useful information. Thank you for publishing it. You may well save people thousands of dollars down the road.
You are correct in that the GM information on circuit and analysis is useless.

 

Thank you for the kind reply. I have never been part of any forum before. Was not sure where to post this. Hope others can find it. Seems like a technical library would be useful. Best wishes to all the Cadi owners out there for 2020!

 

Thanks so much for the new information J&MR. More on the nonelectronic part of this issue. MY info relates to a 2008 STS. This mod can be done without removing the steering wheel from the car. Remove the air bag AFTER disconnecting the battery for a period of time by inserting a coat hanger diameter rod into the small hole on each side. The rod should go in 1.5 inches and meet resistance. Slightly push against the resistance to unlatch that side of the air bag. After both sides are unlatched, pull airbag away from wheel and unplug the 2 connectors (locking tabs on the flat face of each connector, then squeeze clips on each side). The control module is inside/under the spoke that does not have any buttons. The spoke cover can be removed by removing 2 Torq screws to free the more central end of the spoke. The other end is attached by a plastic square peg in a square hole in the wheel. No latch - just pry it off. Do not pry on the soft aluminum shield or you will damage it (ask me how I know). There are 2 phillips screws attaching the control module to the cover. The module can be opened by releasing 4 clips on the module. Hope this helps someone with the mechanics. I have pics if needed.Corrections/comments welcomed.
J&MR please provide us with the extra info you offered. Especially show exactly where the resister terminates. One side is clearly to a small hole in the board. The other end = not so much. How did you come up with 10K ohms? Can we vary that depending on our personal heater resistances? Details of bench tests? Again thanks

 

The resistor terminates between R13 and R14 which has a small via hole there that I may have drilled larger to fit the resistor wire into. The other end is +5V on pin 1 of U1. I enhanced the photo with the general circuit traces in question. I described the theory behind the mod. I don't have any photos of the bench setup. The board is nicely marked with each input/output pin. I used a bench power supply and a big ass power resistor ( hard to find ) for a load. If you can get a power resistor close to your steering wheel heater resistance then you can play with it on the bench to get a working solution. A lower value resistor is not going to hurt you unless you pull up the current sense so high it thinks there is a shorted out heater which will act the same as a high resistance heater. Chip is made to rest in a sweet spot of somewhere between 1.64V to somewhere above 1.7V ( I did not explore the shorted cutoff value ). Hope attached picture will explain more when you zoom in. I should have taken a picture of the bench setup. I also have a brand new control module I need to get rid of if anyone is interested.