Suspension flat / Fault code: 'B22/3(Rear level sensor) No signal'

[Nod]

2004 E320 Wagon, rear suspension stopped inflating both sides. Happened on very wet day, as to whether this is a coincidence, I am unsure.
Dash shows Red Error screen, 'Stop car visit workshop'.
Icarsoft MB2 showing Fault code :-
B22/3(Rear level sensor) No signal

Replaced ride height sensor and cleaned and inspected sensor arm and mounting brackets but fault still remains. I have found the relay and Ohms is okay and it seems to click ok. Think the fuse is number 37 inside the side of the drivers dash, that checks out ok.
Would the fault lay maybe in the harness/ connector that plugs into the ride height sensor? Heard this harness can go bad.

At abit of a loss and am think the fault lies pre- sensor. I guess will take the rear wheel liner out of passenger rear arch and get to the other end of the sensor harness where it plugs into car and check the continuity of the pins.
Any ideas?

 

[Uncle Benz]

Definitely wiring next

 

[alexanderfoti]

Check for supply, ground and signal return at sensor. If fine. Test again at ecu, if missing, wire broken somewhere.

 

[Nod]

Check for supply, ground and signal return at sensor. If fine. Test again at ecu, if missing, wire broken somewhere.

Many thanks for the assistance and guidance.
How do I go about testing for the 'supply, ground and signal return' at the sensor? I,e I cannot put a multimeter on it as its plugged it? I noticed the Icarsoft is saying the Sensor is getting about 4v, which I think would be the supply?

 

[alexanderfoti]

You need a multimeter and some backprobe pins.

One wire (brown) will be ground. The other 2 will be signal supply and return, you need to probe them whilst its connected.

Yes should be a 5v sensor, so the supply will be 5v, and the signal will be something between 2v and 4.5v depending on position usually.

 

[Nod]

You need a multimeter and some backprobe pins.

One wire (brown) will be ground. The other 2 will be signal supply and return, you need to probe them whilst its connected.

Yes should be a 5v sensor, so the supply will be 5v, and the signal will be something between 2v and 4.5v depending on position usually.

Thanks again.
The supply appears to be present then, its 3.96V
Backprobe pins new to me, I usually have made very crude things up to imitate them by poking bits of wire in etc, which probably isn't a good idea ultimately, when I short them out on something!
Would these do the job?

How do the backprobe pins work? Do you actually pierce the casing with them, or the insulation of the wire itself to make a connection? Are they kinda like needles?

Sorry for my ignorance, as I only am familiar with very basic electronic testing and methods etc.

 

[alexanderfoti]

The poke through the back of the connector into the terminals, like shown in the left most image you posted. You dont poke through the insulation with them, they are as you say, like very fine needles.

 

[Nod]

The poke through the back of the connector into the terminals, like shown in the left most image you posted. You dont poke through the insulation with them, they are as you say, like very fine needles.

Oh thanks so much. I will order some right now.
Will be really useful for other things also, rather than poking bits of wire into the connector pins etc.
A 'must have' really to keep alongside the multimeter.

 

[Nod]

Check for supply, ground and signal return at sensor. If fine. Test again at ecu, if missing, wire broken somewhere.

Update:-
I had the idea to disconnect the harness from the wheel arch to the rear sensor itself and check the continuity on the 4 pins. All checks out good, so I am assuming that section of lead is all fine.
Bearing in mind that the sensor is getting its power it appears by the Icarsoft, does this mean using the process of elimination that the longer section of wiring to the ECU may have a break or the connector plug to the ECU?
Again the error code is B22/3(Rear level sensor) No signal

How do I check the signal is getting to the ECU? which according to the error message it is not I guess.
So would this mean the fault lies in the section of wire from the rear wheel arch plug to the ECU?

N.B : Also it appears that the harnesses rubber plug that connects into the sensor is totally sealed when connected to the sensor, don't think it is possible to backprobe it. As said though the sensor is getting its power and the harness has continuity on all 4 pins.

 

[Nod]

Also the bar mechanism that is bolted to the sensor lever arm and sits on the chassis above.... I noticed when I got it off it had quite alot of play on the swivel joints. Could this be faulty and not swivelling properly(because of the excess play on swivel joints) thus causing the level sensor arm to not move properly, i.e then not triggering the relay?
I may get under it and try and force the lever arm to the north and see if that triggers the air pump.

 

[Nod]

Check for supply, ground and signal return at sensor. If fine. Test again at ecu, if missing, wire broken somewhere.

Thinking fault may lay at at the ECU end, or section of cable between ECU and wheel arch. How do I check for signal on Ecu end?

Think the sensor bar mechanism is ok and not the culprit. I took the sensor off and moved the arm around, could not get it to trigger pump.

 

[Nod]

Seems the sensor is giving a signal, like 3-4v. I just jumped the relay pins 30 and 87 and the air pump comes on. It appears that even when left running the bags are not inflating one cm even.
So would the fault lay either in the Air pump not working correctly(even though its chugging away) or a break in the air supply line?
Possibly more likely to be a break in the supply line that the pump itself? (before I go tearing into the pump).

 

[Uncle Benz]

The bags have a solenoid valve on the top that opens when signalled to both allow air in and out. Just running the pump won’t automatically raise the suspension

 

[Uncle Benz]

 

[Nod]

The bags have a solenoid valve on the top that opens when signalled to both allow air in and out. Just running the pump won’t automatically raise the suspension

Aah, yes I forgot that, i.e the Solenoid valve, I have replaced the airstruts so am familiar with the valves on top.
The Icarsoft fault reader is showing on live data like 4v volts odd so some signal is on the sensor itself but it appear it isn't getting back to the ECU as the fault code is : B22/3 Rear level sensor : No signal

Also I did take the cable lead from the wheel arch to the sensor off and check the 4 pins for continuity, which was good.
I ordered a new relay(yet to arrive)as am not totally sure if the old one is functioning as it should, it does sound slightly sticky when you apply voltage to it off the car.

Update :-
Just went out to the car and scanned the fault codes again..... I glance at the car(jacked up high on one side with the wheel off), one side has mysteriously (over)inflated and the other side a fair bit also! Just wondering if somehow it has corrected itself? Possible water ingress somewhere along the circuit/ cable? This did all happen on a ridiculously wet day.

Well I guess will see by putting the car on level ground and test drive. One side is up very high compared to the other but guess it would be, as one side was jacked right up high and its trying to self level.

To recap, I have fitted another sensor, inspected and checked the 4 pin cable for continuity and plugged/ unplugged it and had the relay in and out but other than that haven't really done anything. Seems to have a mind of its own and find it really odd how its somehow started inflating, I guess whilst I been starting the engine on and off without actually noticing it had inflated.

 

[Snake Charmer]

My 53 registered S211 is in storage at the moment and did something similar recently. The rear dropped and sat on the stops so I started the car to get the rear back up then placed a low axle stand under the towbar.
A few weeks later I started the car and noticed the pump continuously running so I removed the axle stand and the car sat low, no dash warnings and did not rise so even with the engine running so I left it.
Opeing the door a couple of times since the pump runs for a short while and cuts out but the rear stays down. Sunday, same thing opening the door, pump runs for a short time. Started the car and no dash warning but straight away the rear rises.
Voodoo.

 

[Nod]

Appears mine has not corrected itself (or behaved mysteriously like the last post!)
Idiot brains here(me) left an axle stand under the diff and the suspension was sagging down giving the false impression it had rose high! Hahah- got my hopes up there, only to get 'that sinking feeling (literally)' when I removed the rogue axle stand and the thing dismally sunk to the floor!
...Back to square one...

Could it be the relay causing it? The Icarsoft does state the fault as 'b22/3: no signal' but also says in live data that the signal is about 3-4v odd, presume that is at the actual sensor reading and not at the ECU end?

How does the system work exactly? The sensor sends a signal to the ECU and if that is in range to wake up the pump. the ecu then sends a signal to the Relay to trigger and switch on the air pump? Could it be that the signal from the sensor isn't getting to the ECU in the first place (section of cable from Rear Wheel arch to ECU) so with no signal it is not triggering the relay? As said I inspected and checked the 4 pin rear cable section from the rear wheel arch to the sensor itself and it appeared to have continuity.
How do I check the first longer section of cable, or even get to it come to that? if you take the side undertray off is it accessible to inspect/ unplug etc?

 

[Snake Charmer]

Looks fairly simple when you look at this....



Then this lot gets involved!

 

[Nod]

Holy Mother Mary! (Thanks for the diagrams and pics BTW)

I looked at the first diagram and pic and thought, "Oh that looks well simple! I will soon have this fixed either with a new relay or at worst a new N97 Rear Axle Control Unit"....
Then I saw the 2nd diagram !

Anyone wanna buy a nice E320 with 'slight suspension fault...' !?

Well, I guess maybe not to get too daunted by the 2nd Diagram(or maybe get very daunted?!) but alot of that probably doesn't really apply to the airmatic side of things(tell myself that to make myself feel better!)
Well, what I am gonna hope for is that the new relay solves issue before I go tearing into all that and probably messing a load of other things up also. Are the N97 units renowned for going bad? or is it more likely a relay would commit suicide and give up the ghost? the latter I hope....

 

[Snake Charmer]

Can you get the pump to run or test with the iCarsoft MB2?