Tow bar installation issue
Hi, I have 2016 bmw 520d and last week had westfalia detachable Tow bar with vehicle specific 13 pin electrics installed at a registered installer. Shortly after leaving I had warning about tyre pressure sensor failure. This is still present despite installer disconnecting electrics and running diagnostics. I have now booked car into bmw for them to investigate.
My questions are twofold. Firstly is this a common problem. Secondly, what do people think regarding liability. Bmw will undoubtedly say no warranty cover, even though there is possibility of it being a coincidence.
The installer has tried all he can but ultimately cannot resolve. The sensors need fixing and I feel unhappy paying out if my own pocket. It may of course be a simple and cheap resolution. Will know in a few days.
Any advice gratefully received.
Pete
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Hi, it's not a reset. The message is that the sensor has failed, which means it can't read tyre pressures, or set them. Tyres are correctly inflated, checked them.
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The tyre pressure monitoring sensors on a BMW are usually in the valve of the tyre. Its is unlikely that the installation of the towbar would have any effect on these sensors unless rear wheels were removed and the pressures altered. I have 320d with a westfalia detachable tow bar with 13pin electrics and didn't have any issues after installation. The wheels did not have to be removed either. Maybe just a coincidence 😀
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When I owned a 2010 520d out of curiosity I asked the mechanic how the TPM worked. He told me it was all part of the ABS system which monitored wheel rotation and not the valve.
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There are two different systems whatever flavour of car. TPMS comes as direct or indirect. Direct has a pressure/temp sensor within the tyre valve which transmits back to a box of electrickery in the car & tells the driver the exact pressure of each wheel. Indirect uses the ABS system to look for a wheel that is going slightly faster that the others. When it detects a faster wheel, the driver gets a message that one of the tyres is soft ..... it's up to the driver then to look for it.
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I could be corrected but I think that VW have similar system working off the ABS.
I had no trouble with the tyre monitoring system until I had to replace an alloy wheel (VW genuine £600 !!!) after a pothole incident. Since then the monitor comes up not infrequently, although the wheel is balanced, wheel nuts tight, pressures correct.
it may pay to check tyre wear, tracking, balance etc.
Next car I am going to buy will have minimal electronic bits, probably a Suziki Jimny, Spec not changed in 14 years !
Or or maybe the sensor has failed !
Rgds
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I don't know BMW. Tow bar electrics are usually a loom that extends the original car wiring. So a lead comes from the fuse box that takes the power to the back of the car. A module in the rear then splits it a number of ways. Wires come from lights etc to the module. These wires act as sensors. So if the brake lights go the module picks up a current from the brake light and puts power to the caravan brake lights. Problems can occur where the towing loom meets the car one. At one brake cluster for example the original plug is removed and the tow bar loom fitted. The original plug is then put into the back of the towing loom socket. This means no wires are cut. So you might remove the tow socket at say the lights and put the original one back on. This means the tow bar electrics won't work but if the tps sensor then goes off you'll know it's the tow bar electrics. If not then you know and you can replace the plugs. Check in the handbook about batteries. If permitted I would also try disconnecting the battery, and reconnecting it. Leave disconnected for more than 20 minutes. This should clear any memory glitches.
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Hi all,
Thanks for the replies. Car went into bmw today and after 2 hours of problem solving they found earth connection to tyre pressure sensor receiver wasn't in, so must have been taken out during tow bar installation. All working ok now, just need the Tow bar electrics reconnecting and we're good to go.
Pete
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The installer was very fair in all this - yes they made a mistake, but they tried all they could to resolve and when i told them how much BMW charged me to fix, he asked for my card and put that money straight back on it.
Mistakes do happen, but can't fault him once problem was found.
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