Wonder if that is why our BMW SUV has a small battery next to the large AGM battery in the rear. They put them in series to operate the electric power assist. Don't know if 24 volts is used anywhere else or perhaps the system operates at a lower voltage and has the extra in reserve.

 

Cars all still use a 12V, if they have two batteries it's to increase the amp draw (or keep steering assist in a start/stop event). The battery can't take sudden current draws over a specific value the chemistry prevents it. Alternators can, but need to be running, if not below the set point then the voltage will drop, kicking on the alternator. Most if not all low voltage faults/events in a car are transitory in nature and highly dependent on loading and temperature.

Parts need to be robust to these transitory things. your car load sheds systems when voltage is an issue (like heated seats) but typically for such a short duration that you don't even notice it. BMW and Ford both have complex battery management systems in their cars. GM doesn't, they are more simplistic, although they do load shed more (since they like to put in the smallest alternator possible).

 

The second smaller battery is typically installed if your model has the "Stop-Start" feature.

 

Sudden loss of steering assist is a problem. I don't care what the engineers give for a reason. If the engineers know the reason- fix the problem in production and give the current owners a resolution. The loss of assist is there and does occur without warning. In the parking lot at 3 mph is an inconvenience. Wheel to to wheel competition at 160+ mph is another matter and could be catastrophic. For crying out loud, the GM fix for loss of EPS assist on a track car is to add a modified C6 rear brake duct to act as a cooler instead of properly correcting a known problem. GM has integrated so many modules in C7's that need to talk to each other, a hydraulic retrofit may not be feasible without some serious code rewrite. i.e.- adding the Chevy Performance Z06 brake upgrade to a Stingray.

 

Sorry if this sounds rude but reading comprehension and physics must not be your strong suit. A loss of assist at 160 MPH would be unnoticeable. Because at 160 MPH your steering system is providing ZERO gain, it's all driver torque. At any speed above 100 this is true. Between 50 and 100 gain is marginal. The steering system really is doing a lot of work under 50 mph and the most at parking speeds (drastically so under 5 mph).

Solving loss of assist fully is impossible. You can't solve the "loss of power" failure from a battery that dies, unless you have two batteries.

This methodology would have to be cascaded to the entire system you basically need a fully redundant electrical system. Probably this is where the industry will go, but in the short term common hardware failures (like sensors) will probably be made redundant.

This still doesn't as I said solve the issue. What SW can and will do in the short term is attempt to control the loss of assist. Ramp rates are better than a step, but this can't be done in all cases. If I have a micro controller failure then I'm SOL, it's a drop to zero assist.

No current module in the car is as complex as power steering (except hybrid powertrains). Traditional ECMs if the electronics fail stall the engine, as the worst case. TCM's put the transmission into a limp home. ABS modules disable traction control, stability control, and ABS but brake boost is still mechanical (for now). All of those failures are mitigated in the same way as power steering is (electronics basically turn off) but don't generate the complaints. My feeling is people expect to be able to steer a car with their pinky and any greater effort to them is considered unacceptable. The fear people have is because they can perceive the difference in steering. Most people don't use ABS, TCS, and ESC every time they stop so an ABS module failure goes unnoticed. So while the loss of features is similar in the customers mind steering loss somehow is "worse" when in reality it's equal.

 

I think it should be noted that loss of assist is not the worst failure, or even second worse failure for power steering.

The worst is "unintended steering" or what many people call a "self steer." This is the motor providing excessive assist with or against you as the driver. The thing to note is you CANNOT control this. If a motor in an EPS goes to full power, your wheel will spin so fast it can break your hand. This failure is 100% made sure it cannot happen as it would be catastrophic. The failure mode when a self steer happens? Pull assist, immediately (in under 20 ms), and return to manual steering.

The second worst failure is similar, but it's over gaining your driver input, such that you have an ever increasing sinusoids output (as you try to catch the steering and correct it the over boost actually shoots you too far the other direction). Like self-steer this is an unacceptable failure. The solution like self steer is to again, pull assist, immediately.

So because these two failures were the focus of all the safety critical diagnostics in EPS, the default way to handle a failure was to pull assist. Hence the large issue with customers, as pulling assist is to them unacceptable.

I will tell you this, you would take a loss of assist any day of the week versus those other two failures. That's what engineers have been doing, protecting you from those.

EDIT: As an FYI the Corvette EPS motor is a 5 Nm Motor, it has a ratio of 20:1 versus the steering wheel (so motor angle/torque to steering wheel angle/torque). This means full motor torque of 5 Nm manifests its self as 100 Nm of torque at the steering wheel. For your information when you have assist, 5 Nm of torque at the steering wheel is a lot, the sensor actually only measures up to 10 Nm for your input. Even in pure manual mode you are putting in at most 30 Nm of torque (this would be at parking), unless you REALLY man handle it. So if you think parking with no assist is difficult, imagine tripling that force, and then trying to FIGHT IT. That's what a self-steer would do, which is to say if it happened at speed your car would make an immediate turn (left of right) and there would be nothing you could do. Hence this is why THIS FAILURE is the #1 thing that needs to be prevented.

EDIT2: https://www.automotive-iq.com/chassi...ver-been-safer

 

[QUOTE=NYVette2112;1595268199]So are you guys still having the issue ?

Just a quick update on mine in case anyone is interested.
I haven't had the issue for a month. I average about 2 drives per week.

Last thing I did, was push on all the connections and cables around the EPS motor.
Not sure if that did anything.
Of course now that I mention this, will most likely go our next drive.

Also had it at the dealer last week for oil change and I mentioned it to them. They did not see a log in the computer. Basically told me to drive it there next time it happens.

 

[QUOTE=NYVette2112;1595467085]Since they replaced the entire rack in my car it's been perfect. My car is a daily driver and the issue became worse as time went on, eventually it got to a point where it was happening multiple times per day. When it first started it was a lot more intermittent and the dealer told me the same thing, no codes. While it's possible that your issue was just something loose, I doubt it. If I were you, I'd put as many miles on it as u can so you can to duplicate the issue and get it taken care of.

 

I just went into my garage and tried turning my steering wheel with the car off. It is not hard at all. It actually feels like the manual steering that I had in my 1971 Camaro. Maybe I am too strong

 

[QUOTE=VistaVette;1595467223]Glad your issue is behind you.

 

NYVette, Hmm, did you notice if the Torque Sensor connector on the ECU was loose?

VistaVette (in his other thread) had a "bad" torque sensor DTC, this can be caused by a bad cable (or a bad sensor). If the cable from the torque sensor is not fully seated (this is done at the supplier plant) then it's possible during driving it can wiggle off. Once it's off for that power cycle the power steering is disabled, but on the next cycle if the connection is good it would come back.

If this is all caused by something as simple as a bad batch of seated connectors from Bosch's plant then it's quite embarrassing for them. Because all those replaced gears will technically be good parts...

 

Well its much better than when my steering locked up on my 85 Supra.
Car was broken into and ignition was broken. I started it with a screwdriver and drove for a couple of months with out an issue. There was a part missing and no parts store or dealer could identify it.
After about 2 months of occasional very spirited driving. Going through an intersection slowly the steering wheel locked. No prob, happened to point me right into a parking lot. Wedge my screw driver into a slot to prevent the steering from locking. All good for a few weeks as long as the screw driver didn't come out. Well of course one day cruising on the bumpy side road at about 45 mph. Screwdriver fell out, I said oh crap and luckily was able to slow enough and went up on an embankment seemed like in slow motion. I was like on a 45 degree angle leaning on the drivers side door. Was a bit embarrassing as cars went by. Thank goodness didnt hit anything. I guess it was young stupid luck.
Needless to say. Then next day I went to multiple junk yards until a guy was nice enough to pull out the ignition switch from a wrecked celica and there was some little piece that I needed.
Still counting my lucky stars that I was driving for months with a steering wheel that could have locked at anytime.

 

[QUOTE=VistaVette;1595467223]Glad your issue has been resolved. Mine has been working flawlessly since I had my rack replaced too and I also DD it and have probably put over 1,500 miles on it since.

 

Sometimes, I just have to wonder how I ever made it out of being young. Every person I know has some story like the above or ones that I used to do.

 

Great story - I can't believe any of us are still around with the types of cars we drove around as young men. My '66 Beetle had no floors. My buddies '74 MGB had no floor so we put ply-wood down but never bolted the seats in so we would just rock back and forth as we drove..the stories go on and on

 

Finally had time to take my 2017 GS to the dealer and was stunned at what they found:

"DTC 0545 3A steering wheel torque sensor incorrect component installed."

"Electric belt drive rack and pinion steering gear replaced."

How does it happen that an incorrect component is installed in the steering wheel torque sensor causing the power steering to fail multiple times? Why are incorrect components even available to be installed? What is the quality control failure that lets this happen?

Perhaps Corvette supervisors could let us know what is going on.

 

Does seem strange, it's not like they make other car in Bowling Green!

 

You can't take the DTC description literally. So before you fly off the handle and make assumptions, calm down. It's not anything like you think it is.

That's a Torque Sensor fault DTC, which is internal to the steering system. VistaVette had the same code.

Basically if the Torque Sensor (located in the pinion tower on the gear) is damaged (unlikely due to the intermittent nature of your faults), the cable is damaged (possibly as a short/no short condition would produce an intermittent issue), or a bad/loose cable connection to the ECU (connector not seated properly) you would get this DTC.

So likely it was a bad cable or improperly connected cable.

Funny thing is, the cable can be replaced, but GM won't do it, because you have to remove the input pinion cover.

So basically this was a supplier manufacturing error, and likely these gears are totally fine. I myself think it's an improperly connected cable.

 

Don't further that incorrect view. The part isn't made by GM, Torque Sensor is internal to the Steering System. It's located in the pinion tower.

The Torque Sensor Cable is the one shown in this picture. It comes as part of the gear.



The plastic "top" above where the cable goes into the pinion tower is what needs to be removed so you can "unplug" the cable inside the pinion. The other end is a regular connector on the ECU.

 

Here are more detailed photos I found online (since I don't have access to any gear anymore other than the one in my car)



Close up of the pinion tower and the cover, remove the plastic cover (after taking out the two screws and you can see the internal "connector" it's basically a clip



Here is the entire length of the wire, including the ECU connector.