Well this won't help with the situation but I have to agree with Don B above in that I have studied the manuals (I'm a geek like that) and I still don't understand 100% how the darn system behaves. I had 3 months of maddening issues last year and I will say that if you have a strut that leaks air, even a little, it will fool you for weeks chasing down other perceived issues. Part of my ignorance comes from the fact that with the suspension you really need the proper diagnostic software to not be guessing and most of us don't have that at our disposal. When I was learning years ago I had a mentor that taught me to always look at the simplest things first before heading into the weeds diagnostically. 99% of the time he was right. So here I tend to believe it has to be something simple as the car was working before the transmission work. I hate to say it but if the car is being passed on to a young driver the cost of converting to car to coilovers, and doing away with what I find is the biggest challenge with these cars as they age, might be money and time better spent. But that suggestion usually can fill an entire thread with opinions.

 

Quick update for problem front struts down at lowest, rear at highest.
1) Fitted new seal in compressor, although did not think that was the problem.
Connected to 12V battery to check motor works and solenoid clicks.

2) On the off chance one of 2 front height sensors maybe has corroded connector.
Removed sensor plugs and cleaned with spray.
The plugs are a PIA to remove, having locking tabs at top and bottom.
Very difficult to deal with having all the suspension hardware in the way, and humans only having two hands.
Ended up busting the plug locking tabs which are very fragile and 18 years old.
Photo shows the locking ramp on top of the unit, and there is one on the bottom.
They have to be released simultaneously while also pulling on the plug.

3) Started engine with car on hoist and holding front struts about half way up.
Compressor did not run, front struts not pressurising.

So I will look under the spare wheel for the solenoid block and reservoir.

Question: Is there one fuse that could make the sytem dead ?

Question: Anybody experimented by connecting the compressor to a battery to fill the reservoir.
Followed by manually operating the solenoids to apply air to the struts ( if possible ).


Height sensor plug

Height sensor unit and plug

 

Quick update for problem front struts down at lowest, rear at highest.
1) Fitted new seal in compressor, although did not think that was the problem.
Connected to 12V battery to check motor works and solenoid clicks.

2) On the off chance one of 2 front height sensors maybe has corroded connector.
Removed sensor plugs and cleaned with spray.
The plugs are a PIA to remove, having locking tabs at top and bottom.
Very difficult to deal with having all the suspension hardware in the way, and humans only having two hands.
Ended up busting the plug locking tabs which are very fragile and 18 years old.
Photo shows the locking ramp on top of the unit, and there is one on the bottom.
They have to be released simultaneously while also pulling on the plug.

3) Started engine with car on hoist and holding front struts about half way up.
Compressor did not run, front struts not pressurising.

So I will look under the spare wheel for the solenoid block and reservoir.

Question: Is there one fuse that could make the sytem dead ?

Question: Anybody experimented by connecting the compressor to a battery to fill the reservoir.
Followed by manually operating the solenoids to apply air to the struts ( if possible ).


Height sensor plug

Height sensor unit and plug

 

Forgot to mention:
Unhooked battery and discharged stay alive caps before starting engine.
Did not help.

 

Hi Richard,

When you unhooked the battery, did you touch the negative cable terminal to the positive terminal for at least two minutes? That is required to drain the keep-alive-memory capacitors, and turning the key to position II (Ignition ON) may help drain the caps in more of the modules.

Also, the ride height sensor electrical connector in your photo appears to be wet with oil. Is that penetrating oil you applied to aid in disconnecting, or oil that had contaminated the connector from some other source? You'll definitely want to clean that with zero-residue electronic contact cleaner or other zero-residue solvent since the oil can add resistance to the electrical connections and cause the signals to the ASM to be incorrect.

When I break the retaining tabs on brittle old connectors, I clean the connector then use a dab or blob of silicone sealant across the seam of the two halves of the connector to hold them together. Once the sealant cures it does a good job of keeping the connector together, but it's easy to separate the connector if necessary in the future. Don't smooth the sealant flat or you may have to use a knife to cut through it. Just apply a blob that you'll be able to grab and pull off.

Cheers,

Don

 

Thanks for feedback Don.
Yes, shorted battery cables to discharge caps.
If caps have reverse protection diodes in front of them that does not do much of course.
Did not have ignition turned on, that may help depending on how the switch energises the system.

I used an Australian made product caled RP7 to flush the height sensor unit and plug.
It is similar to WD40 but has more lubricity and I use it a lot on my Jahgs and also in my electronics manufaturing business.
Certainly does not affect resistance. Apparently the height sensor has a hall effect device, not likely to be a problem.
And yes, made sure the plugs stay in place with silastic for exactly the reasons you give.

Next step is to ask my stepson where he put the scanner and I will see if I have any useful code data.
If I were a betting man I would put my bet on the ASM control unit having a sudden failure.
The problem was sudden, the height sensors ( if working ) tell the ASM to raise the struts and if needed run thecompressor.
The compressor does not run so far.

I have "Jaguar2004MYElectricalGuide.pdf". Looks like a lot to read to zero in on the ASM and circuitry.

 

My recollection is that the ignition switch connects some system grounds/earths, so it certainly could assist in some draining keep-alive-memory caps.


Since some sensor signals are parsed in tenths and even hundredths of an ohm, any added resistance at the connector is cumulative with all other resistance in the circuit (corrosion on connectors, ground points, etc.). WD40,dielectric grease and other lubricants (probably including Selleys RP7) are poor conductors at best and insulators at worst, and can potentially reduce the contact area between connector pins or even block contact entirely, so I personally recommend cleaning connectors with zero-residue products and ensuring they are clean and dry before re-connecting them. In the U.S., CRC Electronic Contact Cleaner is a popular product. You may be right that a little added resistance at the connector for a Hall-effect sensor may be inconsequential.


Air Suspension DTCs are typically C-prefix (Chassis), B-prefix (Body), and U-prefix (Network) codes. Most generic OBDII scanners can only read the P-prefix (Powertrain) codes, so they are not helpful in diagnosing air suspension issues.


ASM failure has been very rare. In fact, I'm struggling to remember a single instance when replacing the ASM solved a suspension malfunction. Maybe someone else will remember.

It seems far more likely that your issue is related to having the car on the lift, possibly combined with leaks in your front air springs. Have you been able to drive the car with all four wheels moving at over 2 mph / 3 km/h to see if the ASM may just be in Jacking Mode?

Cheers,

Don

 

Back to the problem.
Quite correct Don, my scanner did not reveal any codes for suspension.
The instrument cluster is warning of low suspension.
If the ASM generates that error message then there is a reasonable chance it is O.K.
The fact you have no memory of an ASM failure is most welcome.
My stepson has a good mechanic friend with a Snap-On scanner which is much more comprehensive.
Hope to use it next weekend and it should be able to reset the ASM if that is the headache.
Following your suggestion I will short the battery cables with ignition switch on before trying the Snap-On.

The odd thing is that car has been up and down on the hoist many times.
Recently more often than average while fixing the ZF.
Why suddenly the ASM would decide to lower the front to min, and raise rear to max ?

With front at min it will not clear hoist arms. However with help from stepson can release it next weekend.
There is enough room to drive it at up to 10kmh over short distance before hitting the big dip at end of driveway.

Not sure I agree with your comment on connectors.
In my factory we make test equipment with high electronic content.
The equipment is used for field testing in many parts of the world.
It gets slung onto trucks and bounced around in harsh conditions.
Recently we ran into trouble with a few customer complaints of loss of measurement accuracy by anyhing from 0.02% to 1%.
The measurement board is mounted on IDC type connectors and we suspected possible change in connector resistance.
Many Google searches showed some inconsistency on the subject, but there seems to be agreement that vibration and thermal expansion/contraction will cause most connector pins to gradually wear away the pin coating to reveal the base metal.
That causes corrosion in the contact area which may well increase resistance.
There is a protective gel which is claimed to prevent this. I forget the brand name, I have bought 2 tubes of it for the factory.
It is approved by Ford and some other car makers and it is claimed they use it on new cars to mitigate connector problems.

Using it may help our equipment, the jury is still out on the issue.
In theory the connector resistance of concern is not a significant factor in the measurement accuracy.
As you will know it pays to devise circuits where measurements are from voltage dividers which are far more tolerant of connector resistance.
Depending on very low connector resistance for accuracy is a recipe for problems.

I guess once the X350 is in the hands of my stepson I will have withdrawall symptoms.
Did not realise how pleasant it is to drive until I bought the XF.

 

Agreed, but off the top of my head, few sensors in the X350 are set up as a voltage dividers. The throttle position sensor and accelerator pedal position sensors come to mind. Other critical sensors, such as the coolant temperature, intake air temperature, engine oil temperature and fuel temperature sensors are simple thermistors, so added resistance in their circuits can cause the ECM to, for example, provide incorrect fuel injector pulse duration.

Cheers,

Don

 

Yes, those sensors are set up purely as resistance elements which makes sense.
The XJ-S for instance is notorious for problems with the coolant sensor connector going open circuit or high resistance and screwing up the A/F ratio.
It is a concern modern cars have many computer type modules and sensors with collectively many, many hiundreds of connector pins which over time can go open circuit or high resistance.
That is not a user friendly environment for the DIY brigade to work in.
It needs high end scanners with all the software to interrogate and possibly adjust/reset every parameter that affects the car functioning.
That does not line up with manufaturers wanting to give as much work as possible to dealers.

 

It certainly does.
Problem of front struts totally down, rear ones totally up now fixed.
You might recall I was giving the 2003 XJ to my stepson after buying the 2017 XF.
We messed about for a whle checking all the usual suspects, new pump seal and battery on/off a few times with no luck.
My stepson has a mechanic friend who is pretty clued up, and he has an oldish Range Rover with similar suspension.
He also has a high end Snap-On scanner much more expensive than mine.
He came along to my garage with my step son and tried his scanner on the car, but nothing really obvious to see.

I was not there at the time, but they dropped the car down from the hoist, ran the engine, drove the car a few times back and forth in the garage.
VOILA ! Now the struts are where they should be. The scanner must have reset something, so much for reliable software.
Now one very happy step son.
There is a slow leak in at least one strut, because after sitting for a week not driven there is a "Low supension" message but it pumps up again ater a few minutes driving.

Must say some regret handing over the car. I always thought the suspension a bit "floaty" after driving my XJ-Ss and previous XJ6s, but otherwise a very nice car to drive.
With luck my stepson will have no great maintenance/repair events and the car will be around a while yet.

 

Pump up car until the low suspension message is gone. Open the trunk (boot), lift the floor cover and the foam protector beneath it to expose the air tank with tubes. Spray the tubes with soapy water. If you see bubbles you found your leak. Much simpler than replacing a strut (air spring) and a common area that leaks.

 

Thans for info.
I will tell my step son to check it out.