I don't have an F-body, and the installation on my Fiero is different so pictures or that won't be of much use to you.

Regrding problem #1: I slid the circuit board (wrapped in a little tape for insulation) in the free space on the steering wheel's top.

If the cruise buttons don't work, triple check the 12 pin connector inside the steering wheel. Apparently GM used several different (and of course incompatible) pinouts on that connector. Of course the wiring colors are also different between vehicles, else it would have been too easy. Easiest is to get the steering wheel harness from the vehicle mentioned in the instructions from the junkyard. Should only be a few bucks and way easier than repinning the connector.

 

well i hope to see the finished work when done. I want to do the same. If not im gonna have to settle for the momo trek r in my 02 z28

 

Wow, talk about resurrecting a thread from the dead :-D
Airbag systems are always surrounded by a mist of secrecy, much like the A/C people try to tell you what they do is rocket science. Yes, airbag systems are critical systems, but so are brakes, and everyone changes their own pads.

Okay, I've been on the airbag design team of a major GM supplier, so I am arguably more knowledgeable than the average technician. We also supplied airbag tech to the other two of the big three as well as European car makers. Here's my $0.02.

The airbag systems varied widely. Let me explain how they work and then you decide whether or not you want to move a modern airbag to the old control module. The following applies mainly to GM.

In the 80s GM started with a purely mechanical system with masses and springs and contacts. Early F-body SRS schematic. To make sure the airbag squib (firing pellet) fires, 12V are converted to 36V, but this is not really necessary. You just want to get as much energy into the squib to set off the explosion. This happens for driver and passenger, and those two 36V and (as backup) 12V ignition are fed to a "high side switch", which closes on hard deceleration, like e.g. hard braking. This effectively "arms" the system, hence the term "arming switch". It should be set to around 1g, so it armes every time you hit the brakes hard. This feeds high voltage to the plus side of the passenger and driver squibs. To complete the circuit there are two more switches closing the circuit to ground, the "discrimination sensors", which are switches installed in the nose of the car and near the passengers which decide if the crash event is reason enough to fire. The "control module" is called "Diagnostic and Energy Reserve Module", i.e. it provides 36V and checks if any switches are stuck by measuring the values of large shunt resistors built into the switches. These combined resistors are so large (>10k) that the current is not sufficient to trigger the squib. The squib itself has about 3 Ohms resistance, so with 12V that means a current of 4A, equals 48W equals 48 J/s. Short a 3 Amp fuse and observe the flash and you get the idea of what happens inside the squib. Main point is: the DERM does lots of measuring when the system is not active and sets the lamp on faults, but activation of the squib was as simple as closing two mechanical switches. The switches were not particularly adapted to a particular model. It's low-tech like dropping an anchor. Oh, and there was no CAN bus in sight, GM used the UART bus, which was an RS232 type bus system, a predecessor of their Class2 and later GMLAN. And that bus was purely for diagnostics. But I digress.

Auto makers realized that masses and spring are not really precision instruments, so generation 2 arrived: the DERM was now called SDM (Sensing and Diagnostic Module) or SRS (Safety Restraint System). Basic functions still remained, but 12V were now deemed sufficient. Components are shared between many makes models and makeres, so all squibs that I've come across at that time were 3.3 Ohms, and we would use 3.3 Ohms/4W resistors as dummies on our test setups (we didn't have airbags in the labs when developing software obviously). The SDM also contains capacitors to provide for some autonomy in case the battery is disconnected during the crash, and keeps enough to fire the squibs on energy reserve if necessary. This is also why you need to disconnect the battery and wait when working on an airbag system: you need to wait for the energy reserve to drain. The SDM would also include the former "arming switch", still a ball and a spring, but much smaller and mounted on a circuit board. But still: it was now called "safing sensor", because it was a non-software-controlled part of the firing circuit that would prevent the software from firing the squib accidentally. The discriminating sensors were replaced with one or more semiconductor accelerometers that would measure deceleration and decide when the best time is to fire the squib. Note I highlighted "time". If you fire too early, your face hits the wheel and the bag has deflated, too soon and you hit the inflating bag. The SDM calculates (or rather guesstimates) the displacement of the driver's head (predicted displacement) and all in all each crash is different so there's a lot of guessing going on. The timing isn't all THAT critical, and there's a reason why crash tests are made with 80kg 6ft dummies on brand new cars. Put a 60lb skinny female or a big guy into a car that has had welding done to the front frame, the timing will be completely different. But: the firing part itself is again no issue: it is still a switch being closed to ground. The SDM will constantly run tests and measure squib resistance to make sure it's still 3.3 Ohms plus/minus some margin. If resistance is too high or too low, you'd get the airbag light. And in a crash situation, the bags are all inflated after 30-50ms. No matter what wheel, no matter what manufacturer. But you can't just use any SDM in your car for two reasons: 1) the firing algorithm is tuned to your vehicle, sometimes even differently when you have different options, and 2) because we're now in the Class2 era, and the SDM will want to check VIN to make sure it's in the right car and track a few bus variables like speed or brake pedal status (usually purely for crash recording, but without those messages being on the bus the module will set the fault lamp and likely not be ready to fire).

So, let's apply this to your C6 wheel. The wheel is in the same position as your old one, the bag when inflated will try to protect you same as the old bag, although the new bag will probably be smaller because back in the old days one couldn't be sure people were using safety belts. Your old module is tuned to your car, so you need to keep that, but on the airbag side all you need to keep the module happy is present it with a 3.3 Ohms squib, which pretty much all airbags I've come across share. But YMMV. Don't measure the Ohms with a handheld Ohmmeter, just to be safe! But if you look at the airbag I'm pretty sure you'll see two connectors. Why? Because you have two (!) squibs! The C6 very likely has a dual stage airbag incorporating two squibs which the module can decide to fire together or in sequence, depending on the situation. For instance, it's not uncommon for a second crash to happen after the first one, then the second squib can reinflate the bag a second time, or firing them together fills the bag quicker for high speed crashes (these can be problematic because everything happens so quickly that in theory the SDM should have wanted to fire the airbag before the crash. Now, your old module can not handle two squibs. You could wire them in series, but that would set off the SDM because resistance is wrong. You could wire them in parallel, agan the SDM would notice. You could compensate with parallel or serial resistors, but that would only trick the SDM while wasting firing energy possibly to a point that the squib no longer fires (because it only gets 1/4 of the original firing energy). Bottomline: You should only hook up the main squib, if the squibs have different sizes. It would be better if you found a mechanically compatible airbag with a single connector, because that'll have a single squib. Hook it up, and your old SDM or DERM will be happy, and it will be able to fire your new bag. And to the people advocating to keep the old bag because it's safer: Those airbags are now 40 years old, it's not guaranteed they'll still fire, and if they do, if they can do it in the 30-50ms. But your new bag will likely be smaller than the old one, offering less cushion. Then again, the new one may inflate quicker and provide more protection. You won't know unless you put the setup through a series of crash tests, which you obviously won't.

Bottomline: it's doable, but is it safe? Nobody knows. Drive carefully.

 

Long time on this... Wow interesting it got bumped.

At some point I bought an entire steering column from a CTS for a song more than just the shaft, so I've got everything I need to adapt, and I have a wheel, and an airbag. It is a dual stage, yes, but I'm going to only hook up what I think is the primary one, and I'm going to short circuit the pins of the second squib so that there isn't any risk whatsoever of the open pins somehow getting a static discharge that blows it randomly (doubtful but maybe). I worked with airbags for a short time at my old job position and we always shorted the pins before doing anything else with them (checking them out, disposing, etc) so I'll play by the same safety rules now that I know more.

I've re-read this thread a few times, then I recently remembered I have a new gauge overlay, so I just bought a new cluster... Then stumbled across another of LT4vert's threads with the carputer thing that you made years ago, and found my posts that I not only bought that but also had bought a cluster off ebay for dirt about 7 years ago. What? I don't remember that I guess I have a spare cluster in case I really screw it up the first time around with my planned mods. Now I wonder where the stuff is, and what else do I have lying around that I forgot about?

Maybe I'll be able to spend some time on this thing eventually. Since getting married in 2017 and moving to an apartment and the car in storage, we bought a house in 2019, had 3 kids, blah blah... car is running at least lol, been driving it. But winter hit, they threw crap all over the roads again, so the car now sleeps. I'm thinking maybe while sleeping I'll do some surgery on it and see about getting my new wheel installed. But then, I can't leave things well enough alone, so I've been looking at the wiring diagram of the switches on my wheel, the diagrams for the switches on the column itself, and electrically I think I can make everything work. Now physically fitting it all? That's another question. It would be cool if I can somehow fab it up. That's going to take more head scratching and mocking up stuff out and in the car.

Wish me luck.