Just read an article that changing the ride height (lowering the car) requires a control module update to tell the car what the new ride height is so the computer does not think the car is always under load with the lower height. Each lower control arm does have a ride height sensor so the car needs to know the ride height, just not sure what the car does with this info?

or is this just fake news?

 

Never heard of anyone doing that. The base car with MSRC, and all Z51s, Z06s and E-Rays have the ability for the user to lower the suspension, and I've never seen anything from GM that says you need to update any modules when you do so.

 

Thanks for the reply, I figured this was bogus as I live on these forums and never heard of this? 4 plus years into the C8 run I figured this would have come out somewhere.

 

If lowering is accomplished in accordance with what is in the Owners Manual for track use, no relearn is indicated. Documentation does not address what might be necessary if lowering is accomplished using an aftermarket kit. There is a Front Suspension Position Sensor Trim Height Learn in the Service Manual.

In the Track Events and Competitive Driving section of the manual, it says that front shocks without front lift, and rear shocks can be lowered for track use. It says nothing about a relearn process.

However if lowering the car using an aftermarket product, that might be a different story. There can be issues associated with that, and there is a bulletin about it advising dealers that "before any diagnosis of the front lift system takes place, the front shocks should be inspected to confirm they have not been modified. The E60 front lift system shocks should not be modified to lower the vehicle in any way. Lowering the lift actuator may cause internal damage to the part. Repairs to the front lift system after the shocks modification should NOT be submitted as a warranty repair. Damage to suspension components caused by modifying vehicle height outside of factory settings will not be covered by the vehicle warranty."

https://dot.report/bulletins/10215636

Some forum members have used lowering kits successfully, other have reported issues.

There is relearn procedure in the Service Manual - Front Suspension Position Sensor Trim Height Learn
It says the " front suspension position sensor trim height learn should be performed any time a Suspension Position Sensor is removed or replaced, or if the Front Suspension Leveling/Lifting Hydraulic Power Pack Module is replaced." However, while the Service Manual instructs the tech to inspect for aftermarket lowering kits, it does not contain procedures related to what might or might not be necessary if an aftermarket lowering kit is installed.

 

Nope thats a crock of ****. LOL I have lowered ALL my cars including all my C5's, C7, and C8. Other then dragging my front splitter over everything, no issues.

 

What is th relearn procedure?!??

Has anyone else had these message show up?

"Maximum speed 80mph, Shocks inoperative, service ride control"

I thought it was because I broke the clips that connect to the top of the magnetic shocks when I dropped the rear cradle but I've replaced them and the ride height sensors too...

I'm also getting a U0123 code "Lost communication with Vehicle Dynamics Control Module."

I couldn't find much info online...where is this module?

 

The procedure you asked about is attached. It is all initiated and accomplished using a scan tool.

 

I have a front end lift and lowered with paragon collars. I am going into dealer for new tires (I think a set of P4S mounted and balanced for $1200 is not too bad of a price for a dealer!) I could ask the corvette tech to try this relearn procedure on my car, but I am a little hesitant because my car runs fine and I have no lift error messages.
Will this procedure trigger an error because the car is lowered and then create a troublecode that can't be cleared until I remove the collars?

 

I've had zero issues by NOT performing the ride height sensor relearn procedure after lowering both my C7 & C8, but curiosity got the better I me today... I performed the procedure using my Launch Creader Elite scan tool just now. I'll report back if I notice anything different with how the shocks behave or car rides.

 

Thanks all,
I'm currently dealing with a no comms issue. I have the "service ride control, shocks inoperative, max speed 80mph" messages. I suspect I accidentally cut the harness when doing clutch job. I have not had time to tinker with it.

Let us know your results with the relearn procedure.

(2013 Corvette Grand Sport, manual transmission)

 

@Kracka I'll be interested to hear if you find any difference.

 

I didn't drive it tonight, but plan to take the wife to dinner tomorrow night if nothing else.

 

Alright, drove the car into the office this morning... Overall, the car does feel less bouncy now across transitions or when leaned over in a corner. I'm not going to call this a requirement by any stretch, but if you have access to the scan tool, I'd say its worthwhile to perform the procedure.

 

Any idea what the relearn procedure actually does?

 

My guess: If we are discussing the Front Suspension Position Sensor Trim Height Learn procedure. It is stated that the procedure is to be performed any time a B152 Suspension Position Sensor is removed or replaced, or if the Front Suspension Leveling/Lifting Hydraulic Power Pack Module is replaced. There are several pages in the manual that state the exact trim height measurements and the conditions under which they are to be measured (fuel in tank and loading). I believe that these are supposed to be verified prior to performing the learn procedure. The trim height inspection procedure includes a step to look for aftermarket kits - and the measurements only are applicable for stock set ups. There are no stated provisions for what to do if the measurements are not in spec. So given that the trim height measurements are in spec, the learn procedure is just so that a previously disturbed height sensors can learn the correct trim height position.

That is, if a sensor is removed and/or replaced, it will not go back in exactly as it was before, and difference will initially be perceived as a trim height difference, when it is actually caused by a slight repositioning of the sensor. The learn process tells it that where it is, is the correct trim height. But the trim height itself is always assumed to be in spec.

All just a guess.

 

Thanks Andy. I guess what I was asking is how and what does the trim height learn procedure actually change (how does it make the car act any different)?

 

Yes understood. After writing what I posted, which suggests it calibrates the sensor(s) to the standard trim height, it seemed to me that the question was "well then, what do those ride height sensors that are being calibrated do?" That is how do they affect the the car behavior. In looking into this way in the past, it appears there are at least two sets of sensors (I think with front lift). There are sensors inside of the front shocks, and then there are some external sensors that also seem to measure suspension height. I am not clear on whether the learn process affects them all, or just the external ones mentioned in the explanation. Among the things they do are provide trim height info when the front lift system is used. And, there is some internal headlight leveling (inside of the headlight assembly) that adjusts aim as the suspension moves. Again, I am not clear on whether this just with front lift activation or all the time. And, I do not know if or what else those sensors do. Some of the info is in the Service Manual, but its intent is to diagnose and repair, so the explanations for how things work are not necessarily perfect or complete.

I never found anything that suggested it would affect ride or handling - but I don't dispute it either. I just don't know. They may have some role in mag ride - but that is questionable. I think the sensors for that function are different.

 

I had a DSC Sport Controller on my C7. The controller allowed me to customize my MSRC settings (a lot!). The amount of damping varied with a lot of things and, as I remember, position was one of them. Every time I made a change to the settings I had to reestablish the null position (car sitting level with me sitting in it). So it is quite possible there is some interaction between the lift position inputs and MSRC, especially since MSRC cars can turn a tighter radius at slow speeds.

 

OK - still not a direct answer to the question, but I tried. I went through the manual and attempted to determine how the learn procedure might affect the car - based on the sensors that the learn procedure seems to address. I starting with a specific learn procedure - there are also programming and set up procedures. So I looked that those to the extent they are discussed. Other than affecting headlight leveling and front lift operation, I could not find anything that says it affects ride or handling. Not saying it doesn't, just that I cannot find it. The manual is for diagnosis and repair and not a tutorial on how the car works. I have attached an illustrated write up of what I was able to find. Read or ignore - its ok with me - I had fun looking it up.

 

Andy, thanks for taking the trouble. It was a very complete and deep dive effort as usual. It doesn't look like there would be any compelling reason to buy the X431 scanner tool just to do the ride height learn procedure. I don't need to do the exhaust valve relearn procedure again. I'm still waiting to see if the latest update allows it to do the Hydraulic System Flush procedure properly but am not holding my breath.