Converting back the Z55 Air Ride Suspension

[Joseph Garcia]

I have a question for you folks who have the Z55 suspension and have recorded Tech 2 snapshot data regarding its functions. Specifically, the Damper Actuator Commands for each of the 4 electric shocks, and their % range of dampening while driving.

I am learning more about my Tech 2, and I practiced by monitoring the function of the electric Damper Actuators in all 4 shocks in real time while driving, and what I noticed is that they all stay on 0% pretty much all of the time. The only time that they consistently move above 0%, is when I brake to a stop, with my foot staying on the brake pedal, such as at a stop light. Then, all 4 Damper Actuators show 20%, until I release the brake and start to move forward. Then, all 4 Damper Actuators revert to 0%. Occasionally, I see one or more of the Damper Actuators go to 20%, but never above that. I have no DTC codes related to the suspension.

So, today, I tried out the Tech 2 Snapshot recording and playback process, figuring that the Damper Actuators may be operating between 0% and 95%, but the changes may be occurring too fast for me to see them in real time on the Tech 2, since the actuators can respond to changes within 20 milliseconds. So, I recorded all 4 of the Damper Actuators (3 at a time), and I drove over a dirt road, complete with potholes, rippled bumps and washouts, and tight curves, just to be sure that the electric suspension would have many changes to respond to. When I reviewed the snapshot recordings plots on my Tech 2, the behavior was the same as my real time observations. ==>> The Damper Actuators typically stayed at 0% and occasionally went up to 20% (typically all 4 Damper Actuators changing in unison), but no higher than 20%, even though the Tech 2's vertical axis on the plot showed a potential Damper Actuator range of 5% to 95%.

I not believe that this is expected behavior for the Z55 suspension electric Damper Actuators, but I'd like to hear from you who have the Z55 suspension, and who have observed their operation with the Tech 2 or a similar scanning/programming tool. All of the suspension components are either brand new, or operating within spec, as observed on the Tech 2. The only 2 significant suspension components that have not been replaced are the suspension control module (15095254) and the yaw rate sensor (25930324).

Please give me your thoughts.

 

[George B]

@swathdiver
James, have you logged the damper actuation?

If I get a chance I will take Heidi out with me to see what mine does tonight.

 

[TollKeeper]

This is one I cant help you with. I got snap shot data of staying static.. Esky is leaving my possession tonight, so...

 

[gooffeyguy]

@swathdiver
James, have you logged the damper actuation?

If I get a chance I will take Heidi out with me to see what mine does tonight.

I don't think he has the Z55 suspension

 

[George B]

I don't think he has the Z55 suspension

Oh, yeah… That’s right.

 

[George B]

Here is a log I took this evening. I graphed it for easier viewing. Pretty cool how mine works.

 

[swathdiver]

Here is a log I took this evening. I graphed it for easier viewing. Pretty cool how mine works.

Really cool! Never seen that as mine has a dumb suspension!

 

[Joseph Garcia]

Here is a log I took this evening. I graphed it for easier viewing. Pretty cool how mine works.

Thank you so much, George, for taking the interest and time to record this data from your truck's Z55 suspension for me. VERY much appreciated.

Again, this Forum and its members ROCK!!

That is what I expected to see in damper behavior on my newly installed Z55 suspension components. Yet, I never saw any of the tall spikes that you show on your recording. I have a few questions for you:

1). What is the vertical scale in your plot? 0%-95%

2). What is the level of most of the low 'square wave' spikes? ~20%?

My question to all of you is what would you recommend that I do next in my attempt to get my Z55 suspension to behave as designed? Given my plot results, where all 4 Damper Actuators are in fact responding, but not more than 20%, (appears not to be a damper function issue nor an electrical wiring issue) should I consider replacing my suspension control module (15095254) as the next step?

I will record additional Damper Actuator data in Tow/Haul Mode, just to see if the responses are different than what I see in normal mode.

Please give me your thoughts.

 

[George B]

Thank you so much, George, for taking the interest and time time to record this data from your truck's Z55 suspension for me. VERY much appreciated.

Again, this Forum and its members ROCK!!

That is what I expected to see in damper behavior on my newly installed Z55 suspension components. Yet, I never saw any of the tall spikes that you show on your recording. I have a few questions for you:

1). What is the vertical scale in your plot? 0%-95%

2). What is the level of most of the low 'square wave' spikes? ~20%?

My question to all of you is what would you recommend that I do next in my attempt to get my Z55 suspension to behave as designed? Given my plot results, where all 4 Damper Actuators are in fact responding, but not more than 20%, (appears not to be a damper function issue nor an electrical wiring issue) should I consider replacing my suspension control module (15095254) as the next step?

I will record additional Damper Actuator data in Tow/Haul Mode, just to see if the responses are different than what I see in normal mode.

Please give me your thoughts.

I am unsure of the scale however as Heidi called out numbers during the logging process the highest I recall was 95% and the square wave spikes are 20%. If you watch on a pc in full screen mode you can see the values displayed in the upper left. Go to 0:50 of the video and go full screen. Looks like the upper scale is 100%

 

[George B]

Also, it took quite a jolt to get the 94% spikes in normal mode.

 

[Joseph Garcia]

Thanks, @George B . Your test of Tow Mode intrigued me, so I repeated the same road test and Tech 2 recording with the Tow Mode on. Under this scenario, I did receive a number of 95% spikes, but not nearly as many as your road test generated.

It does not appear that any of the other folks with Z55 suspensions on this Forum have any additional suggestions for me to troubleshoot at this time, so I believe that my next step is to purchase a new ESCM and see if my road test results change to more closely mirror your road test results.

I have read that a new ESCM requires programming/calibration upon installation, but I do not see any functions on my Tech 2 regarding programming/calibrating a new ESCM, other than the Auto Level Control calibration. Is anyone aware of any other required procedures for installing a new ESCM?

 

[George B]

@Joseph Garcia
Do you think you might be worrying about nothing? Maybe our comparison is not apples to apples.
My truck has about 85,600 miles on the original front struts and about 10,000 on Arnott remanufactured rear shocks. I also have 22" wheels with extra load tires which are heavier than your 20" wheels with I assume LTX m/s tires.

Maybe there is more need for actuation with my suspension than yours since this is a smart system and accounts for wear and other conditions. That said I don't know how to test that theory unless I went and put all new components on mine as well to compare to the current equipment you have.

 

[Joseph Garcia]

@Joseph Garcia
Do you think you might be worrying about nothing? Maybe our comparison is not apples to apples.
My truck has about 85,600 miles on the original front struts and about 10,000 on Arnott remanufactured rear shocks. I also have 22" wheels with extra load tires which are heavier than your 20" wheels with I assume LTX m/s tires.

Maybe there is more need for actuation with my suspension than yours since this is a smart system and accounts for wear and other conditions. That said I don't know how to test that theory unless I went and put all new components on mine as well to compare to the current equipment you have.

You do make a good point, George. And, my truck has the Hellwig sway bars, which tend to reduce the overall suspension movements versus the original sway bars. But, I still believe that if only 20% dampening was the max dampening needed in 95+% of the road situations, then the Z55 suspension was not really a significant overall design improvement over 'dumb' suspensions (and, maybe, it wasn't).

Since I'm already many dollars into this suspension rebuild project, I'm leaning toward replacing the ESCM, as $295 is only a relatively small addition to the money already spent on this project. The only other electronic item that I did not change was the yaw rate sensor (another $162).

 

[George B]

You do make a good point, George. And, my truck has the Hellwig sway bars, which tend to reduce the overall suspension movements versus the original sway bars. But, I still believe that if only 20% dampening was the max dampening needed in 95+% of the road situations, then the Z55 suspension was not really a significant overall design improvement over 'dumb' suspensions (and, maybe, it wasn't).

Since I'm already many dollars into this suspension rebuild project, I'm leaning toward replacing the ESCM, as $295 is only a relatively small addition to the money already spent on this project. The only other electronic item that I did not change was the yaw rate sensor (another $162).

Maybe look into if there is an improved calibration for your current ESCM on the AC Delco site?

 

[Joseph Garcia]

The last time that I checked, I did not see an option for updating an ESCM. In fact, I did not even see anything related to the ESCM. Today, I cannot get into the SPS section on the ACDelco site for some unknown reason.

 

[91RS]

Maybe I missed it but what problem do you think you're having now? If you have no DTCs set and the air compressor works then the system should be working. If the system was still disabled then it should have code(s) set.

 

[Joseph Garcia]

Maybe I missed it but what problem do you think you're having now? If you have no DTCs set and the air compressor works then the system should be working. If the system was still disabled then it should have code(s) set.

There is no issue with the air side of the suspension, it is on the electric side that I am having an issue. The issue is that I cannot get any of the 4 the Damper Actuators (solenoids) on the shocks to activate by more than 20% even on the roughest and curvy test road, even though their range of dampening goes from 0% - 95%. This just does not seem right.

 

[Joseph Garcia]

I have made a decision to replace the ESCM, and see if the Damper Actuators then operate in the 0% - 95% range in the normal driving mode. If someone has access to the Service and Repair manual, I'd like to view any content on replacing an ESCM, to see what I need to do to get it operational. I know that I need to an Automatic Level Control calibration with my Tech 2, but I want to see if there any other requirements for this process.

As always, any input is appreciated.

 

[Joseph Garcia]

Update and Solution

I reprogrammed the existing ESCM, and that did not change the response of the 4 Damper Actuators, as they still predominantly ranged between the 0% - 20% settings on my dirt test road. The process to re-program the ESCM was another separate challenge, and I've created a separate thread to discuss that experience (Migration from ACDelco TIS to GM Techline Connect for Tech 2 Users). As such, I removed the existing ESCM and I replaced it with a new ESCM, and then I programmed it to my truck. The old ESCM literally came apart from its frame from corrosion, as I removed it.

The response of the Damper Actuators changed dramatically with the new ESCM, with the range increasing to the full 0% - 95% settings range. In addition, I saw each Damper Actuator fluctuating on its own, rather that all 4 Damper Actuators essentially fluctuating together, as I had with the old ESCM. The movements within this extended range are not as dramatic as the test logged by @George B , and still show more 20% setting than any other setting number, other than 0%, but I believe that the reduced fluctuations are a result of my Hellwig sway bars, which permit very little roll of the truck. I noticed on my dirt road tests that the steering angle, the tilt/roll, and the lateral acceleration of the truck in cornering are large components of what drive the change in the solenoid office settings in the Damper Actuators.

So, at this time, I believe that I have successfully completed the conversion back to the OEM Z55 electronic/air suspension, and I thank all of you who participated virtually on this project and shared your knowledge and sage advice with me.

 

[George B]

Update and Solution

I reprogrammed the existing ESCM, and that did not change the response of the 4 Damper Actuators, as they still predominantly ranged between the 0% - 20% settings on my dirt test road. The process to re-program the ESCM was another separate challenge, and I've created a separate thread to discuss that experience (Migration from ACDelco TIS to GM Techline Connect for Tech 2 Users). As such, I removed the existing ESCM and I replaced it with a new ESCM, and then I programmed it to my truck. The old ESCM literally came apart from its frame from corrosion, as I removed it.

The response of the Damper Actuators changed dramatically with the new ESCM, with the range increasing to the full 0% - 95% settings range. In addition, I saw each Damper Actuator fluctuating on its own, rather that all 4 Damper Actuators essentially fluctuating together, as I had with the old ESCM. The movements within this extended range are not as dramatic as the test logged by @George B , and still show more 20% setting than any other setting number, other than 0%, but I believe that the reduced fluctuations are a result of my Hellwig sway bars, which permit very little roll of the truck. I noticed on my dirt road tests that the steering angle, the tilt/roll, and the lateral acceleration of the truck in cornering are large components of what drive the change in the solenoid office settings in the Damper Actuators.

So, at this time, I believe that I have successfully completed the conversion back to the OEM Z55 electronic/air suspension, and I thank all of you who participated virtually on this project and shared your knowledge and sage advice with me.

Success!