2005 4.8iS Suspension Trouble
 

Having problems with my air suspension, and at a loss for what to do next:

2005 e53 4.8iS with the intermittent Inactive Suspension message, which I finally diagnosed to a bad passenger side front sensor (using INPA). Soon after the sensor was replaced, the rear driver side started sagging to the bump stop and the rear passenger side would also drop but not as much. The system resets itself sometimes to normal height all around, and at other times gets stuck and be completely inactive.

What should I be looking for? Does the system need to be reset/recalibrated after a sensor swap? Or is this an entirely new problem?

I found some issues on my rear air level system that I experimented with that solved my problem.


Jack up the rear on stands.
Remove both rear tires

On both side sensors: the level arms should be 'exercised' to full swing up and down several times, and spray oil into the joint. I confirmed that my level sensor was stuck at 4.4 volts in any position until I disconnected the pillow ball linkage, and operated the level to full swing positive and negative several times. The left side was responding to a level change just not the right. And when I was performing the level calibration procedure, I would call the ECU function to raise the suspension and would be perplexed as to why the airbags would inflate to raise the rear axle and then drop down again. The reasoning is the sensors were not sending accurate feedback voltages from their measurements to the control module.

Perhaps there was dust inside or something. I had this problem on the left side sensor, and then two weeks later on the right side. Which were both solved.

The pillow ball joints need to be spray lubricated, and the linkage needs to be free moving over the balls. Previously mine were corroded and stiff.

The lever arms and the connecting rod must be pushing at the correct angle again once the vehicle is lowered back down.


The calibration procedure was performed using ISTA/D and I can't recall the procedure now but I have it written in my notebook exactly.

Bonus tip: I use the product 'AT-205' in a spray bottle, spray the airbags and I used a gloved hand to get the back side of the airbags. This can prevent cracks. I have cracks in my bags, but I don't have any leaks so I want to keep the rubber from drying out.

Great tip on the AT-205. I want to get some for my CV boots

Thanks this is great info! I guess the sensor swing arms should be considered serviceable items.


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I use it on the CV boots, driveshaft dampeners, rubber mounts, etc.

I recently saw the tip on Scotty's YouTube channel and wanted to get some so I was very glad to see it mentioned. I put some in my Amazon cart so I won't forget.

Yes it does need a reset.

A simple explanation is that the system operates by each sensor providing a voltage value that is read by the control module.

This voltage output varies depending on the position of the arm on the sensor which is linked to the suspension... ie as the suspension moves up or down the voltage output varies and this value is sent to the control module.

When you are 'setting' the ride height you are in effect telling the control module which 'voltage output' you prefer on each of the 4 sensors and thus what ride height you want.

To achieve the correct ride height, the control module just regulates the pumping in or out of air throughout the system to each air shock which in turn moves the suspension up or down to achieve the 'correct' values you've told it ie the ride height.

When you replace a sensor, the voltage outputs are usually different and the system doesn't know where to find the correct value or the sensor output is out of the range it can tolerate.

It then has a fit when things get out of its' range and usually shuts down (inactive) when you manipulate the suspension out of level eg when crossing a driveway access ramp / parking on sloping ground.

Do a reset and you should be good.

Excellent explanation and makes ton of sense, thank you!

And now to the $64,000 question: how do you reset the system? Are there step by step instructions somewhere?

I tried Google and a search in this forum, with no luck.

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Can reset with foxwell NT510/520 I’m sure there is a 30 yr old windowz program in German that can also do it.

There are basically 3 ways to reset the system

1. Take it to your local BMW dealer / indy with software who can (for a fee) reset it and you're good to go...
2. Buy an aftermarket scanner such as a Foxwell NT520. These code readers are handy for quick scanning of errors and diagnosing faults. They can come preset for BMW codes and have a connector to plug straight into your port in the drivers footwell dash area. They also have the ability to do some functions such as reset's of certain items in the car. If you do a search of "foxwell" on this forum you will see lots of threads about using it in various situations
3. You can buy one of two types of software that give you comprehensive 'dealer' level access to the functions of your car. The older one of the two is called INPA and the later version is called ISTA. I have both and prefer ISTA, although some functions on INPA are unique that I can see. If you go this route, you will need a cable which comes with the software and a laptop to load it onto. Various people around sell laptops as older versions only worked with Win XP. Mine works with Win8. Again, if you search around this forum and search for each of those terms, you will find various posts on situations and advice/step by steps provided by the members here.

My advice to you would be if you need the car on the road, take it to a dealer/indy with software and get it reset so you're running in the meantime while you get on ebay, order in a copy of the software/cable and learn how to play with it.

With a 4.8is you WILL need to delve deeper into the suspension quirks sooner or later and a code reader will be insufficient the deeper you go....