Holy crap, thank you for stepping in! Tons of great info!As an engineer who works on electronic power steering (EPS) design / integration into a vehicle, this thread peaks my interest for obvious reasons. No, the company I work for doesn't supply the 2nd Gen Colorado / Canyon steering gears so I do not know specifics and I won't share things I shouldn't.
Great thread and good job investigating this on your own.
I didn't get a chance to read all 100 posts yet in detail, here's some of my thoughts.
On Locked Steering Cause:
1. A chipped rack or pinion tooth causing binding is rare, but can happen due to a high impact event (curb impact, off-roading, etc)
2. Water & Debris intrusion due to leaking boots (bellows) that cause corrosion / contaminant build up on the ball nut and/or rack teeth. This typically happens due to either a cut boot or improper fitting of the clamps. We run destructive testing for this exact scenario, and the pictures you posted look just like our post destructive testing gear tear down. Over time the corrosion / contaminants build up results in lesser assist (higher human input at the steering wheel) and the driver should start to feel or hear a crunching phenomena and possible stickiness during rack movement. The crunching / stickiness / binding are worst after letting the truck sit for a while (overnight), then after you steer left / right the corrosion can "wear-in" to the point where steering starts to feel normal again. Eventually, the corrosion / contaminants either cause a sudden locked steering events requiring very large steering wheel torque by the driver (120+ lb-ft) to break throught the bind or freeze up the whole steering gear. From my experience, the water doesn't intrude into the motor due to a shaft seal, but I'm sure it's happened to someone at some point especially if the motor is below the rack due to packaging reasons.
Torque and Pinion Angle / Position Sensor Connector:
1. There shouldn't be dirt inside the connector. Did you disconnect / reconnect this at some point? Adding a little grease to the connector seal can help prevent future water / contaminant intrusion. Obviously, clean that up as best as possible.
2. If you lose electrical connection between the torque sensors and motor, you will lose assist.
3. If you disconnect the torque sensor connector while the vehicle / steering gear is powered on, you WILL set trouble codes. Typically, reconnecting and cycling ignition will put the trouble codes into history.
4. Torque sensors use a change in the magnetic flux to calculate the driver input torque, so the teeth / gaps you mentioned in post #76 (Steering locked up on freeway - the investigation begins) aren't gears you're feeling engage a tooth at a time nor is the cause of notchy steering feeling. See this US patent as a reference: US9302700B2 - Torque sensor and power steering system using the torque sensor - Google Patents
5. From post #93 (Steering locked up on freeway - the investigation begins), since you reassembled the gear back together not in the same position relative to each other from original, you'll need to clear the learned value and/or retrim the pinion position sensor (S.A.S - steering angle sensor I assume). If the after reinstalling the gear, the pinion sensor reads say 200 degrees at actual mechanical center this is likely this is causing errors in the angle hand off to the ABS brakes computer, setting the stabilitrak warning light.
Other Notes (in no particular order):
1. The tie rods are designed to be the weak point and buckle prior to a damaging load causing rack deformation, EPS housing cracking, etc. Keep this in mind if modifying or beefing up your tie rods, like adding tie rod sleeves or replacing with Heim joints.
2. If using Oetiker clamps for the boots, make sure to have the right tool and avoid damage to the boot during removal. Just buy new Oetiker clamps for reinstall if questionable.
3. EPS is reliable, there's vehicles on the road for decades now (yeah, you could claim my bias here). As with anything, once you start causing events outside the range of original design you will cause the part to eventually fail.
4. Loss of assist from EPS is controllable per ISO safety standards, there's a test for loss of assist while steering into a curve at speed and the steering wheel effort by the human driver must be below a certain torque based on vehicle classification. However, during loss of assist the steering effort by the driver is very heavy especially when vehicle is static or low speeds (less than 3-5mph). Steering a full size truck with no assist is difficult and I'm a pretty fit younger man, so I know my wife couldn't do it no assist.
5. The ball nut acts as a lead screw to translate the rotational torque from the motor into linear force. The tolerance for the balls and rack is high, therefore sensitive to contaminant intrusion.
Let me know if could clarify anything else.
The rough action with slightly increases effort was exactly my experience. The motor had no evidence of water intrusion, so that's good. And I confirmed the lock on the bench, which was cool.
Torque and Pinion Angle / Position Sensor Connector:
I have never touched my connectors until this investigation. In the past, I have experienced smaller episodes of the minor loss of assist at the center, but this time it was coming and going at random. I can only suspect that it was the connector wreaking havoc. I received a scanner today which ended up NOT having the ability to relearn the wheel angle for my model year 🤦🏻♂️🤦🏻♂️🤦🏻♂️🤦🏻♂️🤦🏻♂️, but I did find the live data showing angle was in the 200+degree range like you mentioned. A few codes were thrown, including connection loss at EBCM (Electronic Brake Control Module), and two references to "Invalid data received" from both the power steering control module and EBCM (looking at either modules' codes), one of which followed by "Not plausible". So this all makes sense. I forced her to rotate past where the assist stopped, so she probably read 800+ degrees on a system that might only see ~600 degrees. Pics of the codes below.
I'm well aware of the risks with heim steering. With so many folks paranoid from two instances of broken racks under very extreme conditions, I found it a challenge to see how far I could realistically take this. It likely helps that I'm much more conscious about it than others. People are cutting tie rod sleeves because of those two isolated incidents, instead of being more careful. I ditched the oetiker clamps this time, in favor of basic worm gear clamps. I make enough DIY changes to my toe, so I need quick access to the inner heim without needing to redo a clamp. I have no doubt that the systems are reliable, I just put off replacing the boots a couple weeks too late. The rack was actually quiet and smooth before the water entered. Hilariously, it's the first water that the rack has seen in a out 1.5 years. I started tinkering with new tie rod setups in May of last year. I theorize that the dirt/contaminants accumulated at the "bottom", then once the flood water made it's way in, it stirred up and pushed into the ball nut. So that's what that's called! I'm just glad it happened before the road started to get curvy.
I've done lots of troubleshooting on many things, but to have completely torn into this new system and then have an actual engineer drop facts, was awesome. I appreciate your time.
As for my next steps, I remembered that I have lifetime alignment at Firestone. Just haven't gone since I started messing with tie rods. 😂 Made an appointment with them for Camber, Caster and an SAS relearn (I'll handle my own toe, as always). Says on their appointment generator that they do the SAS relearn, so fingers crossed I can actually get it done. And for free! I'll take my disappointing new scanner with me to reset the codes if they don't do it. Eventually I wanna track down a better condition shaft and ball nut 😂, and get her back to normal. Maybe even look into building the center section brace when it comes back out. 🤷🏻♂️