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Old 03-08-2019, 07:13 PM
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Air compressor turns on when jacking up the car.

I noticed when I jack up my X5 from the front, the air compressor that inflates the rear suspension air bags turns on. is there a way to avoid that? thank you.
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Old 03-09-2019, 08:21 AM
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Originally Posted by Bmwfvr View Post
I noticed when I jack up my X5 from the front, the air compressor that inflates the rear suspension air bags turns on. is there a way to avoid that? thank you.

When you raise the vehicle the ride height sensors at the rear axle sense a change in "ride height", and trigger the compressor. I've never found this to be much of a problem, but if you want to avoid it either pull the fuse or disconnect the plug at the compressor.
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Old 03-09-2019, 10:40 AM
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Originally Posted by LightlyToasted View Post
When you raise the vehicle the ride height sensors at the rear axle sense a change in "ride height", and trigger the compressor. I've never found this to be much of a problem, but if you want to avoid it either pull the fuse or disconnect the plug at the compressor.
Ok so it's normal. Didn't want to overwork the compressor cause it kept turning on and off as i was lifting the front. There has to be some sort of service mode so the compressor doesn't come on while the car is being lifted.

Thanks.
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Old 03-09-2019, 01:28 PM
ard ard is offline
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How often do you jack up the front? 3 or 4 times a day?!?

Once every few months will not damage the system. Even 2,3,4 times over the course of a weekend, once every few months is fine.
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Old 03-10-2019, 12:43 AM
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Interesting. I have the opposite effect, but it’s on a lift not a jack so maybe the tilting has some impact. When I put it on the lift and lower it back down the rear sits low. It doesn’t ever leak otherwise so I don’t worry about it. I figure the ride height sensors detect a ‘high’ condition with the wheels dangling and deflate.
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Old 03-10-2019, 11:05 AM
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Originally Posted by absentmathis View Post
Interesting. I have the opposite effect, but it’s on a lift not a jack so maybe the tilting has some impact. When I put it on the lift and lower it back down the rear sits low. It doesn’t ever leak otherwise so I don’t worry about it. I figure the ride height sensors detect a ‘high’ condition with the wheels dangling and deflate.

Same thing happens to me. When I raise the front the compressor usually comes on. When I raise the rear and lower it back down, vehicle sits low at back until next drive. It seems the system only inflates or deflates when the vehicle is "awake". I've found that even opening a door can wake it up and make the compressor turn on. Anyone know the criteria used for awake and asleep?
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Old 03-10-2019, 01:47 PM
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Awake and asleep are one of the most annoying issues about these cars. Why turn on all the modules when I just opened a door to grab something? And then there's a stupid timeout period even after you lock and arm the alarm. Annoying as fk
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Old 03-11-2019, 08:26 AM
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Originally Posted by robnitro View Post
Awake and asleep are one of the most annoying issues about these cars. Why turn on all the modules when I just opened a door to grab something? And then there's a stupid timeout period even after you lock and arm the alarm. Annoying as fk

Because imagine hopping in the car, hitting engine start, and nothing happens because not everything has woken up yet. Maybe someday cars will be smart enough to know if you're opening the door to drive somewhere vs just to grab something, but alas, today is not that day.
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Old 03-11-2019, 09:39 AM
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Quote:
Originally Posted by robnitro
Awake and asleep are one of the most annoying issues about these cars. Why turn on all the modules when I just opened a door to grab something? And then there's a stupid timeout period even after you lock and arm the alarm. Annoying as fk
All of the modules don't turn on when you wake the car up by opening a door. I believe it is only a few that are associated with a particular bus. The e70 is a new gen BMW with a more complicated communication bus...but the old gen BMWs (like the e38/e39/e46/e53/.etc)...only a few modules on the K-bus & P-bus come online when the door handle is lifted. These are modules that start up in preparation for an all system go scenario (IHKA temp fan sensor, door microswitches etc). If the vehicle was optioned out with all those options like auto climate, anti-theft alarm systems, electric windows, electronic central locking...then it wouldn't be necessary to have these modules come online in expectation:


{this is the old gen BMW Wake-up & Sleep criteria...again the e70 has even more features and more online technology and different bus system and modules...but the criteria is similar}

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Old 03-11-2019, 09:53 AM
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Originally Posted by Bmwfvr View Post
I noticed when I jack up my X5 from the front, the air compressor that inflates the rear suspension air bags turns on. is there a way to avoid that? thank you.
The EHC system (rear air suspension) has multiple modes and parameters it operates within. There is a LIFT PLATFORM mode which may or may not take affect if you're only lifting the front.



The text below is an extract from the online TIS...if you want to see all of the info...click this link: https://www.newtis.info/tisv2/a/en/e...ystems/1odeF1T


The EHC control unit recognises the different operating conditions from the incoming signals and messages. Depending on operating conditions, appropriately adapted control functions are activated.

The following control functions of the single-axle electronic height control are described:
  • Sleep mode
  • Pre-mode (temporary start/run-on)
  • Post-mode (readjustment)
  • Normal operation
  • Drive mode
  • Cornering
  • Twist
  • Level-up function (only E61 All-wheel drive until 09/2006)
  • Inclination detection after tyre pressure loss (only E70, E71 with 8-cylinder engine or option 4UB ”3rd row of seats”)
  • Lifting platform
  • Transport mode
  • Production mode

    Transport and production modes can be set and cancelled with the BMW diagnosis system.
    If transport or production mode is set, ”power economy mode active” will be stored in the fault memory.

Sleep mode
No regulation is performed in sleep mode. Control functions that were started in other control modes are cancelled when sleep mode is activated.



Pre-mode
In pre-mode (temporary start/run-on), changes in load are equalised even as the vehicle occupants are getting in and then again for a certain time (approx. 20 minutes) after the vehicle is shut down.

In pre-mode, the ride height is only regulated to the specified height if it differs significantly from this height. The tolerance range for regulation is approx. 40 millimetres under the mean value (the tolerance range stipulates when the electronic circuitry in the EHC control unit performs regulation).

This tolerance ensures that regulation is only initiated for large loads, to increase ground clearance before pulling away. Small loads produce smaller amounts of spring travel, which are not equalised until the engine is started. These control characteristics reduce load on the battery.
In pre-mode, only the mean value of the two level sensor signals is considered.


Post-mode (readjustment)
Post-mode is used to equalise any inclination before sleep mode is initiated (fast filtering).
Control function is time-limited (approx. 1 minute).
In post-mode, regulation is restricted to a defined tolerance range (+7/-10 mm).



Normal mode
Normal mode refers to the normal operating conditions for the vehicle. Normal mode is initiated by the ”engine running” signal. Regulation is performed within a defined tolerance range on each side (±10 mm, fast filtering).


Drive mode
If a roadspeed signal greater than 1 km/h is detected, the EHC control unit will switch to drive mode.
In drive mode, regulation employs slow filtering. For example, in drive mode, changes in ride height caused by the reduction in the vehicle's weight due to fuel consumption are equalised.


Cornering
The ”cornering” control function prevents adjustments being made when cornering is detected. Slow filtering is suspended and ongoing regulation sequences suspended. Cornering is detected from an incoming transverse acceleration signal (e.g. cornering greater than 2 m/s2, less than 1.4 m/s2 when leaving bend). The DSC control unit transmits the transverse acceleration signal via the K-CAN.


Twist
”Twist” mode prevents equalisation of an inclination caused by driving over an obstacle with one wheel. Equalisation would cause a new inclination after the vehicle is driven off the obstacle, making a new regulation sequence necessary.
If the vehicle is driven onto the kerbstone and stopped, the EHC control unit will switch from drive mode to normal mode. In this control function, the signals from the left and right level sensors are evaluated.
”Twist” control function is activated if the difference in height between the left and right-hand sides exceeds a certain value (e.g. 28 mm).

In this control function, the vehicle's ride height in the middle of the axle is evaluated by the EHC control unit.
If the vehicle is loaded or unloaded, the degree of spring deflection is considered. If this value is outside the defined tolerance range (e.g. ±10 millimetres), regulation is initiated.
The left and right-hand sides of the vehicle are raised or lowered in parallel.
The difference in height between the two sides is maintained.
When the EHC control unit goes into drive mode, control function
”Twist” is terminated. An ongoing regulation sequence will be cancelled. The ”Twist” control function is ended if the height differential between the left and right sides of the vehicle drops below a predefined value.




Inclination detection after tyre pressure loss (only E70, E71 with 8-cylinder engine or option 4UB ”3rd row of seats”)
If the Run Flat Indicator (RPA) or tyre pressure control (RDC) detects a loss of pressure at one wheel, the control function will relieve the load on the affected tyre.
When the tyre pressure loss has been rectified and the Run Flat Indicator / tyre pressure control no longer indicates a pressure loss, this control function will automatically be ended after about 5 minutes with the engine running.


Lifting platform
In the ”Lifting platform” control function, any adjustment is prevented during a wheel change or other work carried out on the lifting platform.
The following conditions trigger the ”Lifting platform” control function:
  • Permissible spring extension exceeded (e.g. more than 50 millimetres, recorded by left and/or right-hand level sensor)
  • Vehicle raised slightly (spring extension e.g. less than 55 millimetres), regulation starts but vehicle is not lowered

The height is stored in the EHC control unit.
A reset is performed when the vehicle is again e.g. 10 millimetres under this stored height or when drive mode is detected.


Transport mode
The specified height is raised in transport mode (e.g. 30 mm). The increased ground clearance guarantees risk-free transportation of the vehicle.

Production mode
Production mode is employed for assembly on the production line and prevents regulation sequences from being initiated.
New EHC control units are delivered with production mode set. Production mode must be cancelled after the new EHC control unit has been installed.



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