Air suspension in firm mode all the time.
Hi, I have a 2008 XJ8 VP that the air suspension seems to be working properly. No DTC's, compressor (new) comes on and turns off no problems. Car levels no problem. On my I930 diagnostic tool when monitoring the PID DAMPER FIRM ERROR it says NO when parked but as soon as I drive off it goes in YES and the dampers are all indeed firm. I checked lots of things and everything seems to work properly. Wheel speed sensors etc. Anyone have any ideas on this one?Can a height sensor cause this? Not sure what is causing it to go into firm mode. Thanks for any help.

 

It can be a leak or it can be a height sensor.
Try jacking up one side and then the other.
When I did that on mine there was a high pitched whistle.

Try also 'painting' some soapy water arond the top of struts
Please post your location and air temperature

 

On a 2007 x358 diesel we tried if it was possible to eliminate the coming back transport mode.
I have a 2003 x350 with over 222k miles second pair of struts. After an icy nightshift the x350 got super stiff plus way too frightening high . I thought it might explode .
Sdd said front and rear left sensors shot.
Went to jaguar dealership and bought 4 new ones 2 front 90€ and 1 rear160€ . All went well i finally realised i could replace the last rear one on the right side too but using a new front sensor and switching the longer arm from the old rear sensor over. 20min with pryer and hairdrier .
perfect improvement in comfort 10 to 15 percent

A couple of days later ordered 3 front ones for the x358 changed the longer rear arms over to the new ones
Installed ,working like it should at first plus a felt 15- 20 percent improvement in comfort( despite 20 inch rims).. after returning from a 20 minute test drive Tom parked the car parallel a wall where the road has a dide incline . So the car stood lower on the right. Next drive same problem is back, transport mode
That was a year ago still did not find the real reason. Car had a crash in the back detected in the boot floor. The connectors on top of the struts might have a problem. One thing for shure it was not the hightsensors

 

For some reason Jag decided the car would be in firm mode at slow speed. Have you checked the readings when going faster?

 

Yes, always in firm even at speed. I 930 always shows DAMPER FIRM ERROR YES. I ordered the SDD software. Hopefully that tells me what is wrong. Shocks hold air fine.

 

SDD will probably point you in the right direction. Since it is put in firm due to any fault in that system it helps to see which is causing the problem. The early XJ8s are problematic if using some of the clones since they only function on CCF cars and not VID block ones. Not sure if the output can be cycled on and off with SDD to see if each works. Some things can and some not. I have a 2004 built in 2003 and a number of clones would not even talk to the ECU!

 

I have been having an error where no DTCs are set but when monitoring my I930 signals when driving the PID Damper Firm error =YES. All shocks are firm. Level is fine. Compressor works as it should. I decided to OHM out the switching solenoids on each shock. ( the solenoids that control soft and firm) Testing the front ones a measure 5.4 ohms on both front shock. The rear ones measure 2.4 ohms on both. Is this correct? I thought they should all measure 5.4 ohms.

 

So I think I figured out my Damper Firm error = YES. I pulled the trunk trunk trim and found to my surprise the rear struts have the tell tale silver cone on top which means they are aftermarket and that they actually don't have a soft mode. I suppose that makes sense now.

 

The cone should be Arnott airstruts

 

Sounds like the Suncore (China) knock-offs that I am using. Thise are all over ebay and 'not-only' @ under $200 per strut.

AFAIK the con-puta logic only GUESSES that they are in firm mode (the powered OFF default) when it cannot detect a solenoid (or "cheater" resistor) drawing current in response to a "comfort mode" (powered ON) ..command..