Yaw Rate Sensor circuit failure? Code C1279

[RodFerris]

Hi, Not quite sure where to post this plea for help as i was investigating two problems, but as this fault code shows up on my ICarsoft under ABS section i have put it here. Please feel free to correct me if its not relevant.
Car is a 2005 3 litre V6 X350 with 80K miles.
First thing i noticed was a Warning light on dash with ASC DSC failure with associated car sliding image. So my first thought was battery, as car has not had a lot of use lately and this came up regularly on my X308 XJ. But also i noticed the suspension was very hard and i could feel every bump.There are no Air suspension faults showing. (Its never been as comfortable as my old X308 to me anyway, but i think this is more to do with the seats in my x308 which are very comfortable) But this was clearly very different to when i bought the car about 14 months ago. Battery is about 3 years old but i charged it up anyway. No Change. ASC fault light was still on and suspension very hard. I connected up my ICarsoft scanner and did a diagnostic test. Under manual scan DTC Code C1279 YAW RATE CIRCUIT FAILURE came up and i could not clear it. Could this yaw rate sensor be my suspension problem too? Also Where can i find the Yaw Rate sensor module? The internet forums suggest its under the centre consul which i have just removed but its not there. I also thought it might be under the spare wheel with the air suspension tank and valve, again no joy. Suspension heights seem low - 360mm on 3 wheels but OSR is only about 330mm
Can anyone help please?
Regards
Rod

[PaulGover]

The yaw sensor is under the J-gate; it's quite small, and has a private CANbus to the ABS/DSC/TC control unit, better known as the brake master control gubbins, with a great big multi-way connector and all the pipes coming out of it. But unless someone's taken an axe to the J-gate or wiring, it should be safe.

OSR ride height low on one side suggests a failed height sensor on that side - possibly it's just become disconnected from the suspension arm, so the air suspension unit thinks its in the right place, even though it isn't. I think alternative causes - leaks or blown air bags - should result in diagnostics for "suspension too low".

I'd sort the suspension issue out first, and then see if the yaw sensor issue goes away. When the various ECUs get conflicting data the programming logic assumes various subsystems aren't working, and their choice can be "baroque" - for example a failed rear wheel speed sensor gets diagnoses as a broken gearbox, yaw sensor and steering sensor, since the ECU believes that one wheel isn't turning and so the car is turning hard to one side, despite all the other evidence to the contrary!

[RodFerris]

Thanks Paul, Thats really helpful. I'll try and have a look at the OSR wheel ride height sensor tomorrow, weather permitting.
If the ride height sensor isn't the culprit, would i need to remove the J gate selector to get to the Yaw sensor? I did remove the centre consul and J gate surround this afternoon but could not see the yaw sensor. I probably missed it if its small as i was expecting something bigger looking at examples for sale on ebay.
Thanks for your reply.
Rod

[PaulGover]

The J-gate assembly shouldn't need removing: you remove the centre console cover and the plastic air duct, then unplug its cables, a bit fiddly as there's a lot in a small space, but all very tidy, and then a couple of small bolts holding it in place. It's probably somewhat more difficult than it sounds as you have to work round the rather rigid "flexible" gear shift cable.

Probably avoid removing it until proven guilty, as the manual warns it's a delicate part that can be damaged by dropping etc.

[RodFerris]

Thanks Paul, very much appreciated. Iv'e just had a quick look with the J gate surround removed and i can just see it under the handbrake switch. I think when i had the centre consul off yesterday the air duct being there made me think that the sensor wasn't there. Now i know differently, thank you very much for that. I won't mess about with it other than check the multiplug/cables going into it for any obvious problem.
The car is booked in for its annual service next Wednesday with Wiltshire Jag in Swindon so will probably get them to scan the car for the suspension problem as the weather here is not too good for crawling around under the car. Won't be easy on the wallet but the car is not very usable as it is. Just hope it will stand the 30 mile trip.
Thanks again for your brilliant information, and i will hopefully post a result at the end of next week.
Regards
Rod

[RodFerris]

Hello,
For anybody interested, or as a reference in case anybody experiences the same problems, the faults have now been diagnosed and repaired by Paul at Wiltshire Independent Jaguar in Swindon. The code C1279 was the Yaw Rate Sensor circuit failure. The (expensive) sensor has been replaced, which cleared the fault. The air suspension issue was caused by a broken nearside Rear Ride Height sensor bracket which was repaired, and what felt like riding on a sheet of board feeling every bump, has now been resolved. (I suspect the potholes that i hit on my way down to South Wales being the culprits)
The car was booked in for its annual service anyway so it made sense to get Wiltshire Jag to do the work as although i was given good advice in this forum as to the problems, i wasn't feeling that confident to carry out the work myself.
Thank you to Paul Gover for his knowledge and communication in pointing me in the right direction to resolve these problems.
Regards
Rod

[PaulGover]

You're welcome. You might try guessing which parts of my X350 I've been taking apart recently