Trailer Stability Assist stuck on

[mijango]

Hi
I towed my camper trailer on the weekend (up to Hawk's Nest, NSW) and as usual unhitched the trailer on Friday night and setup camp.

We went for a drive on Saturday and I noticed the gearing was slightly different (holding 1st for longer) and that the parking sensors weren't working. I am pretty sure the car still thinks the trailer is attached as is in Trailer Assist mode :(

I've since come back home with the trailer and unhitched again and still the problem remains.

Any ideas how to fix? :D

[discotwinturbo]

Weird.

I would try a hard reset first.

Brett..

[Basil135]

Have you (or someone else) installed a trailer module for LED's?

If so, it is either locked into the on position, or gone faulty.

Another alternative, is that a short has occurred between earth & the indicator circuit in the socket.

[mijango]

Thanks guys.

I have fitted in line resistors to the indicator circuits on the trailer, but that was a good 6 or so months ago and til now they've worked perfectly.

If I was to do a hard reset, firstly are there any downsides in doing this, and also how do I do that?;)

[discotwinturbo]

Thanks guys. I have fitted in line resistors to the indicator circuits on the trailer, but that was a good 6 or so months ago and til now they've worked perfectly. If I was to do a hard reset, firstly are there any downsides in doing this, and also how do I do that?;)

No downsides that I am aware of.

Pop bonnet. Put hand brake on and close doors. Wait for hand brake light to go off. Remove negative terminal than positive (if you have a dual battery system that feeds back into the starter then you will need to disconnect it too). Use a metal rod or spanner to short the battery cables...not the terminals.

Reverse for reconnection, positive them negative.

See if that fixes it.

If not...you have a short likely in the car trailer connection.

Brett....

[mijango]

So I first checked the trailer for any shorts (just checking that all the various signals and brake lights work) and all seemed ok.
I hooked up the trailer again, and disconnected it, just to see if it would magically remedy itself .. but alas :(

So then tried the hard reset, but again no joy. The hard reset meant I had to reprogram the clock and also the one-touch 'up' for the windows.

So got it booked in with Ayers Automotive to diagnose. I keep telling myself that'll be cheaper than having my wife reversing it into something :angel:

[sniegy]

Have you checked fuses?
Be the first place to look..

[mijango]

I just tried checking the fuses and strangely can't find one for the trailer stability assist. I checked all the other fuses that are related to the trailer tho.

Furthermore, Ayers Auto have had the car today and are originally diagnosed the problem to be in the TSA loom. They have now replaced the trailer module and spent 5hours diagnosing only for me find out problem still remains.
They did mention it was fixed (ie parking sensors working) tho when my wife reversed it out of the garage, the sensors stopped working again.
$840 for nowt!! Grrr..

[LandyAndy]

Thanks guys.

I have fitted in line resistors to the indicator circuits on the trailer, but that was a good 6 or so months ago and til now they've worked perfectly.

If I was to do a hard reset, firstly are there any downsides in doing this, and also how do I do that?;)

Check your resistors for loose or broken connections.
We have a Mercedes prime mover at work,the wiring has failed twice in the last couple of weeks,once on the indicator circuit and once on the reverse beeper circuit.The truck has resistors fitted due to LED trailer lights.When the resistors are faulty you can here the computer looking for the issue when its parked ans ignition off,the faulty resistor makes a clicking sound,much like a shorted electric fence.May not be your issue but worth a look see.May only click when you open the drivers door so get a helper;);););)
GOODLUCK
Andrew

[Graeme]

As I understand it, the only definite information is that the rear parking sensors aren't working when they should be. I would persue a probable wiring fault with the sensors, possibly behind the bumper. I would take it back to where it was attempted to be repaired to ask them to have another look because I would expect some warranty on the work done. My D4 had an intermittent fault caused by a short circuit on a sensor wire that had rubbed on metal.

[SBD4]

I would go with what Graeme said especially if you are not seeing the trailor symbol blinking in the dash when using the indicators. That symbol blinking would prove the TSC is active.

[Redback]

I just tried checking the fuses and strangely can't find one for the trailer stability assist. I checked all the other fuses that are related to the trailer tho.

Furthermore, Ayers Auto have had the car today and are originally diagnosed the problem to be in the TSA loom. They have now replaced the trailer module and spent 5hours diagnosing only for me find out problem still remains.
They did mention it was fixed (ie parking sensors working) tho when my wife reversed it out of the garage, the sensors stopped working again.
$840 for nowt!! Grrr..

That's because it's not electronicly operated, Trailer assist doesn't need the trailer electrics to be connected to work, so the trailer symbol on the dash means nothing in regards to Trailer Assist.

See here
Land Rover Discovery 4 Trailer Stability Assist Video - YouTube

[mijango]

As I understand it, the only definite information is that the rear parking sensors aren't working when they should be. I would persue a probable wiring fault with the sensors, possibly behind the bumper. I would take it back to where it was attempted to be repaired to ask them to have another look because I would expect some warranty on the work done. My D4 had an intermittent fault caused by a short circuit on a sensor wire that had rubbed on metal.

That's pretty much the avenue Ayers have been pursuing but when the IID tool said BOTH front and rear parking sensors were faulty it seemed odd and we assumed (wrongly) replacing the module would fix it.
My gut still tells me there is something in the computer system that thinks the trailer is attached. (Although that said, that wouldn't explain the fault message

When I do reverse I get a longish beep, the parking sensor button flashes and then goes quiet. If I try to push the button to turn it on, nothing. The key though is that I'm sure the gearing is different ( especially when coasting slowly and then accelerating) which feels jerky as the gears change down earlier.

Part of me wants to go back to the main dealer at Artarmon!

[Redback]

That's pretty much the avenue Ayers have been pursuing but when the IID tool said BOTH front and rear parking sensors were faulty it seemed odd and we assumed (wrongly) replacing the module would fix it.
My gut still tells me there is something in the computer system that thinks the trailer is attached. (Although that said, that wouldn't explain the fault message

When I do reverse I get a longish beep, the parking sensor button flashes and then goes quiet. If I try to push the button to turn it on, nothing. The key though is that I'm sure the gearing is different ( especially when coasting slowly and then accelerating) which feels jerky as the gears change down earlier.

Part of me wants to go back to the main dealer at Artarmon!

The only way the system senses the trailer is there, is if the trailer is attached to the car.

Baz.

[mijango]

The only way the system senses the trailer is there, is if the trailer is attached to the car.

Baz.

I'm trying to work out what it is that senses a trailer is attached. Is it the weight on the hitch? Or the electrics being plugged in?

[Basil135]

I'm trying to work out what it is that senses a trailer is attached. Is it the weight on the hitch? Or the electrics being plugged in?
The car senses the extra current draw of the trailers indicators to tell it that it is attached.

[Graeme]

When I do reverse I get a longish beep, the parking sensor button flashes and then goes quiet. If I try to push the button to turn it on, nothing.Typical of a fault, probably short circuit, in the rear sensor wiring. No beep occurs when selecting reverse when it detects that a trailer is attached.

Edit: Front and rear sensors are controlled by the one park assist module. Trailer assist is a function of the ABS module. I suspect that the park assist module was replaced.

[Redback]

I'm trying to work out what it is that senses a trailer is attached. Is it the weight on the hitch? Or the electrics being plugged in?


The car senses the extra current draw of the trailers indicators to tell it that it is attached.

No to both, you need to watch the video above that I posted to clarify my statement, watch it all and listen to what he says at the end, it's only 56sec:cool:

Baz.

[SBD4]

No to both, you need to watch the video above that I posted to clarify my statement, watch it all and listen to what he says at the end, it's only 56sec:cool:

Baz.

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.

[Redback]

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.

X2 what he said.

[Graeme]

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.Not quite on my D4 with my box trailer and its incandescent lights where the reverse sensors are disabled yet the trailer blinker indicator never operates. Perhaps the brake lights draw enough current to trigger the trailer-connected condition (presumably set in the bcu) but the blinker globes don't draw enough to make the bcu think there is a trailer blinker. The trailer indicator operates with my van blinkers though. I'd like the reverse sensors to operate again once the trailer lead is unplugged without having to cycle the ignition.

[mijango]

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?

[Redback]

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.

[baldivistribe]

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

[Graeme]

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.

[Ferret]

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.

[Meken]

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

[mijango]

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!

[Tombie]

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...

[mijango]

Well.. problem solved.. (Though my kids will now enjoy $1,100 less inheritance!)

It was down to a faulty wire at one of the front parking sensors which jumped out when the electrician took the front bar off. It wasn't there previously so had obviously dislodged itself from doing a bit of 4wding on the weekend.

Ayers claimed it's just one of those things with electrics- ie trial and error diagnosis. I can almost see where they are coming from, but it would have left a far less bitter taste in the mouth had they checked this first.

On the other hand I'm happy as at least Disco Dave is back to full strength again!

Hopefully anyone with the problem in the future will find this thread (though it should probably be renamed 'faulty parking sensors'!)

[jonesy63]

Sorry, I haven't been around here for a while - too busy at work. :mad:

If you want to simulate this failure mode - try running into a kangaroo or wallaby, which takes out one or more front parking distance sensors. *** Exactly the same symptoms.


*** Seriously, don't try this! :D

[Redback]

Well.. problem solved.. (Though my kids will now enjoy $1,100 less inheritance!)

It was down to a faulty wire at one of the front parking sensors which jumped out when the electrician took the front bar off. It wasn't there previously so had obviously dislodged itself from doing a bit of 4wding on the weekend.

Ayers claimed it's just one of those things with electrics- ie trial and error diagnosis. I can almost see where they are coming from, but it would have left a far less bitter taste in the mouth had they checked this first.

On the other hand I'm happy as at least Disco Dave is back to full strength again!

Hopefully anyone with the problem in the future will find this thread (though it should probably be renamed 'faulty parking sensors'!)

Any decent auto electrician would have picked up on this, I'd be blaming whoever took the front bumper off.

Baz.

[matti4556]

So Graeme's diagnosis was on the money all along? Seems a lot cheaper than $1100 to check sensor wiring front and back!