Thread: Trailer Stability Assist stuck on

Originally Posted by SBD4

Yes Barry is correct, the trailer electrics do not need to be plugged in for TSC to work - it is a function of the ABS Module as Graeme has stated.

As I understand it, when the electrics are plugged in the engine and gearbox dynamics are changed to accommodate the additional weight being towed and rear sensors turned off all of which is indicated by the blinking symbol on the dash.

So, if you have hard wired resistors into the car to account for LED lights on your trailer and have not provided away to switch them out of the circuit when the trailer is not attached then that would cause the issue too.

Thanks for all the responses. So as I understand it, the video mentions it is the swaying motion while towing that the car recognises and adjusts for, which is the TRailer Stability Assist feature.
Am I right in thinking the adjusted gearing and cancellation of parking sensors become activate when the trailer electrics are plugged in, and therefore is quite separate?

That aside it's the latter that is causing me problems.
To the point on the wired resistors, these are in the trailer not the car, so this shouldn't be causing the car to think a trailer is still connected.
So I'm still trying to work out if the problem is simply the parking sensors, or whether it is more related to the car thinking there is a trailer connected (which would temporarily deactivate the parking sensors) *scratches head*

Do both the front sensors usually also deactivate when reversing with a trailer on?

Originally Posted by mijango

Thanks for all the responses. So as I understand it, the video mentions it is the swaying motion while towing that the car recognises and adjusts for, which is the TRailer Stability Assist feature.
Am I right in thinking the adjusted gearing and cancellation of parking sensors become activate when the trailer electrics are plugged in, and therefore is quite separate?

That aside it's the latter that is causing me problems.
To the point on the wired resistors, these are in the trailer not the car, so this shouldn't be causing the car to think a trailer is still connected.
So I'm still trying to work out if the problem is simply the parking sensors, or whether it is more related to the car thinking there is a trailer connected (which would temporarily deactivate the parking sensors) *scratches head*

Do both the front sensors usually also deactivate when reversing with a trailer on?

Yes that is correct, I would listen to what Graeme is saying.

Baz.

Hello
Possibly could be related to the trailer wiring sockets on the car. I mistakenly sprayed some lanolin around our trailer plugs to prevent the corrosion issue. Now have a similar issue in that the car thinks the trailer is connected so wont auto raise the suspension when selecting low range sand mode. I have to manually do it. I get a message pop up on dash saying something along those lines too.
Cheers
Steve

Originally Posted by mijango

So I'm still trying to work out if the problem is simply the parking sensors, or whether it is more related to the car thinking there is a trailer connected (which would temporarily deactivate the parking sensors) *scratches head*

Perhaps you have never noticed that the normal short beep when reverse is selected does not occur when the trailer is connected. Because there is a beep, whether its a short one that indicates the sensors are indeed working or a long one indicating a sensor error, the vehicle knows that no trailer is attached.

Originally Posted by mijango

Am I right in thinking the adjusted gearing and cancellation of parking sensors become activate when the trailer electrics are plugged in, and therefore is quite separate?

This is true up to a point. Just the act of connecting or unconnecting the trailer is not sufficient to activate/deactivate the reversing sensors. Another event must take place probably related to the sending of an electrical trailer detection pulse.

For instance, when reversing up to my trailer the reversing alarm will sound as I get close. If, without turning off the engine I get out, leaving the drivers door open and plug the trailer in then the reversing alarms will not cancel until I close the drivers door again.

Similarly. If, after the reversing sensors have been disabled by the detection of the trailer I get out of the car (with the engine still running) and disconnect the trailer then the reversing sensors will not be re-enabled again until the car engine is switch off and switch back on again.

This how the reverse sensors behave on my MY11 D4. I have no idea whether the gear box behaves the same but I suspect it probably does.

So, in summary my reversing sensors are always disabled after disconnecting my trailer (and probably gearbox program thinks trailer is still attached) until a restart of the engine has occurred.

The car sends a pulse width modulation to the trailer socket to detect a trailer when the driver door is closed - so after plugging in or unplugging open then close the driver door should do it. The pwm is a couple of different voltages ( 2-3ish) to test for resistance of the circuit- (current flows there is a circuit so car senses trailer attached and bulbs okay ) no trailer no current. Front sensors should stay active when trailer plugged in

Well thanks everyone for your comments.

After multiple conversations with Ayers automotive and lots of diagnosis, it's come to light that the problem is to do with a the parking sensor wiring harness earthing at the front (nothing to do with the trailer at all!). So, sorry for leading you all (and me;-)down the wrong garden path. It's uncanny that it happened when it did though.

It seems there is a bad connection somewhere up front and having taken off the front bar and tested the sensors it is suddenly working again. Over next few days they've said to see how it goes and bring it back in if the problem returns..

I'll let you know if anything else unfolds!

The gear shift etc being different after towing is the adaptive transmission behavior and will move away to your normal driving style over the next few drives.

Glad the Sensor fault has been sorted.

I'd be claiming back some of what you paid for te misdiagnosis...