hasagerkirk
Member Since: 16 Mar 2008
Location: Dubai
Posts: 17
  
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I had a somewhat interesting experience this morning.
I sent my vehicle for 48,000km serviced Monday and I had a few additional items that needed to be attended to, things like: change of brake pads, spare wheel winch not working (the result of having all 5 tires rotated and balanced by a Tire Center), the infamous screeching APB issue had also caught up with me and few other minor things.
I got the vehicle back from LR yesterday, everything was attended to and fixed (the fixing of the APB and a new spare wheel winch was done under warranty) and on the way back to the office noticed a slight ‘bounce’ from the rear end occurring at speeds just over 120 km/h and it felt a little like a puncture. I pulled over, checked the tires – no puncture and no visible problems – but I noticed a slight burning smell just like when a PCB board is burned.
I had a look under the car – and still no visible issues.
I jumped back into the car and drove off – no problems – whatsoever. Drove another 30-40 km yesterday at speeds not exceeding 120 km/h due to traffic. No more problems at all..
This morning I had to drive from Dubai to Abu Dhabi and initially at speeds of 120 km/h – no issue - but as the traffic eased and speed went up to 130 km/h, the ‘bounce’ and noise came back and this time quite violently. At first I thought I had a puncture but as I slowed down it started to feel like a wheel was loose..!!
I pulled over and the smell of burnt “PCB board†was again quite strong but once again all the wheels and tires were OK – nothing wrong.
I cancelled my meetings in Abu Dhabi and returned to LR. As I drove off – again there were no signs of any problems at all.
The drive back to LR was at 110-120 km/h and no issues – normal drive.
When I got to LR – explained the situation to the Service Advisors and there still was a hint of the “PCB†burning smell at the backend.
They figured about 2 hours to check and fix the problem. 4½ hours later the car returned from the test drive and ‘all was fixed’!
I was told that the problem was a software bug in the APB software. This bug would activate the APB ‘under certain circumstances (in my case a certain speed) and that what was creating the smell of burnt PCB.
Unfortunately, the Service Advisor couldn’t quite explain what happened mechanically when the APB activates at speed (his English was not up to scratch and neither is my Indian) but he said they had changed the APB controller and the wheel hubs that are just behind the wheel both left and right rear wheels. All fixed under warranty.
As there was no de-acceleration or braking action happening when the ‘bouncing’ occurred, I would think that the brakes themselves are not activated by the APB over a certain speed but as the software bug kept requesting APB activation, that somehow created a mechanical mismatch in the wheel-hub, creating the bouncing and the PCB burning smell.
I thought I would share this with you, as I had not seen this type of failure yet anywhere. Also, I’m sure there is somebody out there who would know much more about what actually happens if/when the APB is activated at speed and can explain it to me/us.
Cheers.
Lars
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 8th Jan 2009 2:38 pm |
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ThatMartinChap
Member Since: 06 Nov 2007
Location: Deepest Darkest Berkshire
Posts: 696
  
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very interesting - it reminds me of an article I read some time ago where Jaguar had to recall cars when their automatic gearbox software would mistakenly select reverse gear. this was speed defendant also - it only did it at high speed.  Also Gone : MY14 D4 SDV6 HSE : Barolo Black + Almond
Sadly Gone : MY08 D3 TDV6 HSE : Stornoway + Alpaca + Privacy + BAS Remap
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| 8th Jan 2009 2:44 pm |
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