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Discussion Starter #1
Last week I had to take my 2010 Caliber in for his yearly "safety" inspection and received an instantaneous failure because the SRS ("Air Bag") light was on (as it had been since before last Christmas). I don't regard this as a problem because I habitually wear seat-belts and demand that anybody riding with me do likewise; however the State knows more than I do, so it wound up being a $650 tax bill.

That said, being the curious type that I am, I asked the garage to retain the failed part for me -- the "clockspring" module that contains the wiring for (1) all the pushbuttons on the steering wheel and (2) the wires for igniting the pyros that inflate the "air" bags (hint: it's not air or compressed gas in there -- it's rocket-engine exhaust). Likely one of the pyro-ignition traces in the long flexible printed-circuit board that makes up the "clockspring" proper had failed and that was causing the idiot-light to illuminate.

The point of this is that (1) the pyro-ignition connections were easy to identify as those are heavy-current devices and so the connectors are easy to spot (in the 2012, two wire pairs in the wheel, four pins on the back, for the two pieces of ordnance -- with shorting devices when the module is disconnected); there's another 6-pin connector on the dashboard side of the module and a corresponding 6-pin connector on the steering-wheel end (these for all the controls on the steering-wheel). But, there's an additional 4-pin connector that has no corresponding end-point on the wheel proper, and a disassembly of the module points up a printed-circuit board with four(!) optical encoders directly attached to the steering-column, two through a small gear-train. My guess is that this is for the black-box-recorder function and measures steering inputs.

I'm curious how one might "talk" to this thing so I can figure out how precise the angular measurement is. With four separate encoders with different encodings and gearings, my initial guess is that it may be almost good enough for steer-by-wire (if that ever happens).. It's almost certainly on the CAN (Controller Area Network), so that may be a bit of an obstacle, but if I can figure out how to talk to it it'd be rather cool.

Ideas?
 

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Don't take this as gospel but higher end scan tools can read the steering angle sensors in the wheel that are used as part of the stability control (and maybe ABS?). Assuming those ARE angle sensors, such a scanner might give you the info you need.
 

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Discussion Starter #3
I didn't even think about the "stability control" angle, but that makes perfect sense because the thing will need to know what the intended direction is before it can know to "do something" about it. Thanks for pointing that up!

As for whether it's an angle-sensor or not, I can't imagine anything else being keyed onto the steering column with optical encoders reading what the column is doing could be. The primary ring doubles as the release levers for the pawls that release the turn-signal stalk from its activated positions as the steering-wheel rotates. There's one optical encoder on the firewall-side and another on the steering-wheel side, and there's a gear off that ring that has two encoders on its underside. It's a pretty slick piece of design.

I'll toss up a photo of the thing with the covers removed if anybody's interested. This whole thing is an intellectual exercise anyway because I'm the curious type.
 

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2008 Dodge Caliber SXT 2.0
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I didn't even think about the "stability control" angle, but that makes perfect sense because the thing will need to know what the intended direction is before it can know to "do something" about it. Thanks for pointing that up!

As for whether it's an angle-sensor or not, I can't imagine anything else being keyed onto the steering column with optical encoders reading what the column is doing could be. The primary ring doubles as the release levers for the pawls that release the turn-signal stalk from its activated positions as the steering-wheel rotates. There's one optical encoder on the firewall-side and another on the steering-wheel side, and there's a gear off that ring that has two encoders on its underside. It's a pretty slick piece of design.

I'll toss up a photo of the thing with the covers removed if anybody's interested. This whole thing is an intellectual exercise anyway because I'm the curious type.
Did you ever post that picture?
 
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