L322 Accelerometer values

This site contains affiliate links for which LandyZone may be compensated if you make a purchase.
jeremy156

jeremy156

New Member
Posts
7
Location
Southampton, UK
Going over my new-to-me L322 and examining suspension readings because I have an intermittently harsh ride.

I'm curious whether these values look typical? These are taken at standstill, engine off, so not sure why it's showing acceleration both sides. Presumably this is normal "zero-ish" tolerance and not a concern?

2011 L322 4.4 TDV8
 

Attachments

  • accel2.PNG
    accel2.PNG
    47.5 KB · Views: 28
These were mine when I checked them for a another thread. This is for my 2005 L322 and will be slightly different from yours due to calibrated heights and sensor resistance variations. The pictures show the 3 height settings.
 

Attachments

  • Access.jpg
    Access.jpg
    340.2 KB · Views: 20
  • Normal.jpg
    Normal.jpg
    406.8 KB · Views: 20
  • Off road.jpg
    Off road.jpg
    365.2 KB · Views: 18
jeremy156 said:
Going over my new-to-me L322 and examining suspension readings because I have an intermittently harsh ride.

I'm curious whether these values look typical? These are taken at standstill, engine off, so not sure why it's showing acceleration both sides. Presumably this is normal "zero-ish" tolerance and not a concern?

2011 L322 4.4 TDV8
Click to expand...
Moving quite fast for a car that's switched off !! . . . . . . but is that up or down, and how long was it accelerating for ?

https://www.omnicalculator.com/physics/acceleration
1733424660490.png
 
Last edited:
pwood999 said:
Moving quite fast for a car that's switched off !! . . . . . . but is that up or down, and how long was it accelerating for ?

https://www.omnicalculator.com/physics/acceleration
Click to expand...
My point exactly... 0.4ms/s or 0.6ms/s could either be an incorrect reading which *might* be within threshold for the system to decide to firm up... or it could be "noise" and well outside of the threshold at which the dampers tighten.
 
As far as I know, an L322 only has an accelerometer sensor for the SRS system. If you are diagnosing the suspension then your diag is converting height readings into acceleration !!
 
pwood999 said:
As far as I know, an L322 only has an accelerometer sensor for the SRS system. If you are diagnosing the suspension then your diag is converting height readings into acceleration !!
Click to expand...
No the accelerometers control the suspension operations. may also have some control with crash sensors for the SRS.

But the Op doesn't actually say if he has any fault codes for the suspension, So no real fault to see.
Although I would expect a 5v sensor to give a reading of around 1(ish)volt at rest.

J
 
pwood999 said:
Sensor voltage yes somewhere between 0v-5v, but if the car isn't moving surely acceleration should be zero !!
Click to expand...
My understanding is a 0-5v sensors working range is always between 1ish-4ish but never 0 or 5v.
I really should just go out and check shouldnt I ;)

J
 
Just been out to check, cant find that on my GAP (maybe it needs updating)
So if @jeremy156 could direct me to the settings I will try again.
Not tonight though cos grubs up :)

J
 
marjon said:
Just been out to check, cant find that on my GAP (maybe it needs updating)
So if @jeremy156 could direct me to the settings I will try again.
Not tonight though cos grubs up :)

J
Click to expand...
Live Values
Select Live Values...
Complete List...
ADCM - Active Damping
Screenshot 2024-12-06 160156.png


Indeed, I have no error message, just an intermittent rough ride. Sometimes magic carpet, sometimes close to rigid.
 
Ok will have a look.
We have had an issue with the wiring that goes in the top of the front struts (apparently a known issue) for the active dampening but yours seems different.

J
 
Well the values are meaningless, because you cannot be accelerating when the car is stationary. . . . unless JLR assume 0.4-0.6m/s^2 is not moving !! Maybe that's why they take so long to answer the phone !!
 
Sensor supply voltage should be 5.0VDC +/-0.25VDC Also bear in mind that 'we' are moving at (depending where on the planet you are) ~733 miles per hour, so yes, constant speed but acceleration will be measured because it's a vector, not a straight line speed. The value is a relative value, not an absolute and needs to have an 'above zero' value at rest as capacitors cannot 'go negative'.
The sensors in question are exclusively for the adaptive damping and are processed along with other input signals to determine the current applied to the magnetic damping fluid or variable venturi orifices depending upon the type fitted.
The accelerometers measure acceleration in the vertical plane and output a
corresponding analogue signal to the Integrated Suspension Control
Module. The algorithms in the Integrated Suspension Control Module
predict the heave, pitch and roll motions of the vehicle, which are used to
control body modes.

Each accelerometer is connected to the Integrated Suspension Control
Module via three wires, which supply ground, 5 V supply and signal return.

The sensing element comprises a single parallel plate capacitor, one plate of
which moves relative to the other dependent on the force (acceleration)
applied. This causes the capacitance to change as a function of applied
acceleration. This capacitance is compared with a fixed reference capacitor
in a bridge circuit and the signal is processed by means of a dedicated
integrated circuit to generate an output voltage that varies as a function of
applied acceleration. The sensors output a signal voltage of approximately 1
V/g ± 0.05 V/g.
Click to expand...
 
marjon said:
My understanding is a 0-5v sensors working range is always between 1ish-4ish but never 0 or 5v.
I really should just go out and check shouldnt I ;)

J
Click to expand...
Supply voltage is 5V, output voltage should be between 0.5-4.5V, this is so the control module can detect short to ground (<0.5V) and short to positive / open circuit (>4.5V) and set DTC's as appropriate.
 
Well they've applied the wrong term then, it's g - a measure of sustained acceleration. The systems description & operation define it as a measure of 'heave, pitch and roll', not all of which is vertical. m/s2 (the SI measurement of g) can be in any plane, if you look at the orientation of the sensors, you'll see the rearmost one is 90 degrees rotated to the other two.
 
A change in speed relative to, which is why the 'standstill' value isn't zero.
Edit: Actually, it's not a 'steady state', the rotational speed does vary, but it's the rotation that's important - it's a (relatively) constant vector acceleration.
Back to the sensors, they need to be able to measure acceleration or deceleration, hence the mid-range starting value. If it were possible to do it with resistors, it'd be a simple Wheatstone bridge array.
 
Last edited:
You must log in or register to reply here.

Similar threads

P
2012 Range Rover Westminster 4.4 TDV8 Review
Replies
15
Views
18K
2.0_hippo
2.0_hippo
Back
Top