PLEASE HELP AHC pogo stick

[Stricmic000]

More

 

[BEG]

That's some good info. Any closer to chasing down the issue?

 

[Stricmic000]

Nope, i need a different wiring test thing so i can ground the end of the harness but local auto shops were useless so i need to do internet

 

[uHu]

I was hoping you would see this post in the famous thread: Definitive list of AHC maintenance items
Might be what you need.

 

[Stricmic000]

Thanks for looking out! I dont see anything in the last 3 pages that applies to me except maby the shocks "shutting off" due to low pressure making me think my airbags are too high (they are at less than 5psi) but thats not it cause my rear pressure reads 7 when in N and L and 6.8 when in H...and the dampers are in safe mode while in N and L, and its cool to remember that before i had the back of the car lifted on jack stands for 8 hours everything was completely perfect and well within specs (never disconnected any suspension parts just used spring compressors to take springs out)

 

[Stricmic000]

Oh and I have no check engine light and no DCT according to OBDlink even after driving and cycling the heights

 

[Stricmic000]

Took a video just for fun going from H to N

 

[Sargy]

What rear springs do you have?

You also mentioned airbags? Like leveling airbags when towing?

 

[Stricmic000]

What rear springs do you have?

You also mentioned airbags? Like leveling airbags when towing?

yeah airbags inside the coil springs, but htey are at 5 psi or less in L mode and provide no lift especially in N, I have new AHC springs that ive have for about 6 months

 

[Sargy]

yeah airbags inside the coil springs, but htey are at 5 psi or less in L mode and provide no lift especially in N, I have new AHC springs that ive have for about 6 months

Got it.
- Put the truck on low,
- Turn off truck and reset ahc (remove negative battery terminal and wait around 30 seconds before inserting back. VGRS will light up if equipped but will self calibrate after some driving and dissapear)
- Hook up techstream / other device and switch to N mode and send back the new pressure readings front and rear.
- Check to see if pogo stick is still occuring while driving.

Is your rear height sensor in its stock position?

 

[PADDO]

When you’re sitting in park, engine running the front and rear damper settings remain at mid setting (step 8 if the system is working as designed). The adaptive variable dampening doesn’t become active until you’re moving and then it’s a function of speed, braking, acceleration and a few other inputs and it will vary the front and the rear between 1 (soft) and 16 (hard). Bouncing the truck in H and comparing that effort to bouncing in N doesn’t reveal anything about the adaptive variable suspensions performance unfortunately - it’s just bouncing.

 

[Sargy]

@PADDO's knowledge is unreal sometimes

 

[PADDO]

@PADDO's knowledge is unreal sometimes

Nah, it’s all in the books. Books + Techstream + experimentation = results (sometimes)

 

[Stricmic000]

Nah, it’s all in the books. Books + Techstream + experimentation = results (sometimes)

Yes, what I am showing is that it's not just "stiff" its locked out, and when I am driving in H its perfect and I can watch the damping change from 1 to 16 while moving BUT when in N it says (OBDlink) its changing but the rear end is locked out still while saying its going from 1 to 16 just like the front is...hench i have no DCT and the computer thinks everything is good

 

[Stricmic000]

Got it.
- Put the truck on low,
- Turn off truck and reset ahc (remove negative battery terminal and wait around 30 seconds before inserting back. VGRS will light up if equipped but will self calibrate after some driving and dissapear)
- Hook up techstream / other device and switch to N mode and send back the new pressure readings front and rear.
- Check to see if pogo stick is still occuring while driving.

Is your rear height sensor in its stock position?

Okay I put the car in L disconnected the battery for a few minutes hook the battery backup while I was still in L and made sure that my airbags had is absolutely zero pressure in there and then raise the car back up N I felt no change in the rear damping and these are my numbers although I'm not sitting on perfectly level ground at the moment

 

[Stricmic000]

I could swap my old globes on real quick and see if that fixes it (even though they are worn out)...I have another new rear height sensor i could put on and my old one which i think is functioning properly and see if that helps, I followed the wire on the frame from right rear to the front and saw no obvious damage from an exhaust leak....ALL my symptoms happened after I had the rear on jack stands for 8 hours and removed rear springs and put airbags in using spring compressor

 

[Sargy]

Good idea.

 

[PADDO]

Yes, what I am showing is that it's not just "stiff" its locked out, and when I am driving in H its perfect and I can watch the damping change from 1 to 16 while moving BUT when in N it says (OBDlink) its changing but the rear end is locked out still while saying its going from 1 to 16 just like the front is...hench i have no DCT and the computer thinks everything is good

What’s the ride quality like at N with the system manually locked at damper setting step 1 front and rear? If you’re seeing the rear step changing whilst in motion then that suggests the control side of things should be (could be?) ok. I’d love to know what your actual pressures are, via gauge and not from the pressure sensor, at N. Comparing suspension performance at H (and up to the 19mph limit) should be irrelevant because that extra 1.5+ inches over N really bumps the pressures up to the detriment of dampening. Now if dampening is better at H (with higher pressure) then that suggests your pressures at N are too low. Either too high or too low pressure at N, where it’s supposed to be optimized, is bad for damping quality.

 

[Stricmic000]

Nah, it’s all in the books. Books + Techstream + experimentation = results (sometimes)

What’s the ride quality like at N with the system manually locked at damper setting step 1 front and rear? If you’re seeing the rear step changing whilst in motion then that suggests the control side of things should be (could be?) ok. I’d love to know what your actual pressures are, via gauge and not from the pressure sensor, at N. Comparing suspension performance at H (and up to the 19mph limit) should be irrelevant because that extra 1.5+ inches over N really bumps the pressures up to the detriment of dampening. Now if dampening is better at H (with higher pressure) then that suggests your pressures at N are too low. Either too high or too low pressure at N, where it’s supposed to be optimized, is bad for damping quality.

In N the front is great but the back is so stiff I am genuinely afraid I will lose control of the vehicle, it stays locked out even when I bypass it in the DLC3 to do the 16 step test but when in H mode it goes through all 16 steps just fine. My obd2 indicated pressure on rear in H is right at 6.8 and in N and L it stays above 7 but is locked out so the actual ride is pretty much impossible to tell....I might be able to rent a pressure gauge from Autozone and see what it says.

To me the mystery is why does H work but n and l are locked out, my best guess is a broken/melted/smashed wire loom but I'm waiting on a tool to be able to test continuity without removing the harness

It was interesting to me what @Sargy said about his dampers "turning off" when the load is too light, Ive heard this referred to as them going into a safe mode or locking out...I put 450lbs of tires in the back where the seats go and nothing changed so I don't think the pressure is too low

 

[uHu]

In N the front is great but the back is so stiff I am genuinely afraid I will lose control of the vehicle, it stays locked out even when I bypass it in the DLC3 to do the 16 step test but when in H mode it goes through all 16 steps just fine. My obd2 indicated pressure on rear in H is right at 6.8 and in N and L it stays above 7 but is locked out so the actual ride is pretty much impossible to tell....I might be able to rent a pressure gauge from Autozone and see what it says.....

Really puzzling - can't understand what the problem is.
But, in order to not make you more confused, the reading of pressure at the different heights is just nonsense. The are no pressure sensors in the system which can tell you the pressure. There is only one pressure sensor and that is at the pump. The system (the ahc ecu) is designed so that if and when you move from Lo to N, and only then, it will give you a pressure reading. The reading is (a bit) meaningful only if you first are at rest at Lo, and then move undisturbed all the way to N. All other reading are just spurious momentary readings of what the pump is doing just then, and that depends on a lot of non synchronized factors. That's why Paddo mentions gauges, that's the only way of telling what's the real pressure at different levels.

Do you have ohm readings of all the 3 height sensors at different heights, similar to what SlowOnTheBrakes did in the "Definitive" thread? It could be that the lack of a reliable height signal makes the ecu lock out. And it doesn't have to be the rear sensor for the rear end to act up. And, btw, the trouble codes for the ahc are not very reliable. Most possible problems have no error codes at all, and others are just confusing.