Trailer wiring causing limp mode?

[user 1279]

Hi guys, when I'm towing my boat trailer with the lights on, my D40 (2014 series 6 manual) seems to lose all power (cannot rev, no turbo etc). I assume this is limp mode?

As soon as I turn the lights off it returns to normal.

This only seems to occur with my boat trailer, other trailers are ok so it would point to my boat trailer wiring.

However, what would cause this to occur? The lights on the trailer (LEDs) all work fine.

Would appreciate your thoughts!

Cheers.

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[Old.Tony]

That's an interesting fault. It shouldn't happen! I suspect something's wrong with the second pin from the left of the trailer socket on the trailer. That should be the clearance light pin if it's using standard wiring - I always refer to this page for my trailer sockets.

It's curious that it should cause limp mode. I also wonder if there's a cross connection between that and the pin beside it (3rd from the left on the trailer) which may be fed by the car's reversing signal? That could bring the reversing light circuit on, which might indicate to the ECU that your power should be restricted because you're in reverse - it's a bit of a leap, but a possibility.

Try disconnecting those two wires from the trailer socket (you don't need either during the day) and see what it does.

 

[jonney]

does sound like there is a bad connection or something to do with the Lights Wiring to trailer. i would use a multimeter and check for good 12 volt power at the plug harness and at the tail lights, i know you can,t check the LED as there sealed but probe the wire at the tail lights to get the voltage. has to be something very simple.

 

[bods]

That's an interesting fault. It shouldn't happen! I suspect something's wrong with the second pin from the left of the trailer socket on the trailer. That should be the clearance light pin if it's using standard wiring - I always refer to this page for my trailer sockets.

It's curious that it should cause limp mode. I also wonder if there's a cross connection between that and the pin beside it (3rd from the left on the trailer) which may be fed by the car's reversing signal? That could bring the reversing light circuit on, which might indicate to the ECU that your power should be restricted because you're in reverse - it's a bit of a leap, but a possibility.

Try disconnecting those two wires from the trailer socket (you don't need either during the day) and see what it does.

I seem to recall d40s having something where if the brake lights come on, it reduces power. So the only thing I can think of is that when the headlights are on, power is being fed back into the brake light circuit on the vehicle. It could be a stray wire in the trailer plug or a bridged wire somewhere else in the wiring loom, but will take a bit of diagnosis with a multimeter to find the short...

 

[user 1279]

Some interesting comments there guys and it does help. I added a rollbar with the inbuild LED brake light and a friend wired it into the cars trailer plug. Not sure why only my boat trailer does it but the cars trailer plug has been 'messed' with.

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[user 1279]

Actually, come to think of it when I turn my park lights on when the boat trailer is connected it does turn the rollbar brake light on! This is when limp mode or power loss starts. When I turn park lights off its fine again (including turn signals and brake lights on the trailer).

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[user 1279]

I seem to recall d40s having something where if the brake lights come on, it reduces power. So the only thing I can think of is that when the headlights are on, power is being fed back into the brake light circuit on the vehicle. It could be a stray wire in the trailer plug or a bridged wire somewhere else in the wiring loom, but will take a bit of diagnosis with a multimeter to find the short...

This sounds exactly the problem. As I said below, when park lights are on power is being fed back into the brake circuit as it causes my rollbar brake light to come on (as its wired into the trailer socket)...

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[bods]

Sounds like it may be something in the trailer wiring. Can you try the same trailer on a different vehicle and see if the same issue happens?

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[user 1279]

Sounds like it may be something in the trailer wiring. Can you try the same trailer on a different vehicle and see if the same issue happens?

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I dont have access to another car with towball unfortunately but I think (hope) its on the trailer side.

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[bods]

Fair enough. Best bet would be to googe a picture of your trailer plug (unless you know what the pin diagram is) and test for continuity between the tail and brake light circuits. Obviously there is somewhere, it just depends whether it is in the trailer plug itself or one of the connections at the lights on the trailer...

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[bods]

I know this is an old thread, but thought I would add some findings.

My 2010 d22 never did this from the factory, however I recently changed the ecu for one from a 2014 model (same part number but newer revision) and it now does it. I have tested this by holding the manual control lever on the brake controller on with no trailer connected (which brings on the brake lights) and there is a definite engine derate. As soon as the brake lights go off, power is back to normal.

Obviously something has been changed in the later models to bring this into effect.

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[Old.Tony]

Could it be (odd as this may sound) that the brake light circuit is monitored by the ECU, so that if the brakes come on, the engine is treated similarly to being in neutral?

 

[bods]

I would say it is some sort of "feature" that stops you accelerating under full power when the brakes are applied.

It is a dirty word, but the new hiluxes are the same, except they have a warning message come up on the dash cluster screen warning that the accelerator and brake are being pressed together and cuts power completely. You can't rev the motor at all while both pedals are being pressed.

In the d22s at least, you can still accelerate, it is just a form of limp mode. The engine just revs up very slowly.

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[KevinE]

I'm a complete novice when it comes to auto elecs, but I was told by a service manager at a dealer that Nissan re-mapped the ECU in the D22 in 2012.

The brake controller on my 2013 is wired up differently to the one on my old 2010 D22.

Exactly the same brake controller on both of mine & the same guy installed them both:

On this one, the brake controller only fires up once the engine is running.

On the old one, the brake controller used to fire up as soon as the key was turned on at the ignition.

He tried wiring the new one up the way that the old one was wired & it threw a CEL, so he changed it.

Like I said, I'm electronically challenged, so I have no idea on the specifics. But it may pay to get someone who installs them everyday to have a look at it.

Good luck with it!

 

[bods]

I'm not really sure what you're getting at. I only mentioned noticing the power loss with activating the manual switch on the brake controller to eliminate pressing the brake pedal hard enough to activate the vehicle brakes.

My brake controller works fine, I can't understand how you would have any issues wiring them up, they generally only have 4 wires...

Anyway, I was just adding to this thread that the later model d22s also have this "feature" (if you'd call it that) of reducing power output when the brake lights are on.

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[KevinE]

"Anyway, I was just adding to this thread that the later model d22s also have this "feature" (if you'd call it that) of reducing power output when the brake lights are on."

My 2013 doesn't do that. It never has from new.

 

[bods]

Fair enough, but if you read the earlier posts, I said I fitted an ecu from a 2014 model...

It never did it with my factory 2010 ecu either, which I tried with the brake controller fitted before changing the ecu.

I should also add, my original ecu has a part number 23710-vn37a

The new one I fitted has a part number 23710-vn57a

So obviously something has changed. If your 2013 doesn't do it, maybe it was brought in for the 2014 model?

 

[Tms40]

I had this problem today. I'm very electronically challenged but when I got back in the car at the the servo after fuelling up I noticed that the LED screen on my brake controller was displaying 51. Usually it is blank when the brake is not applied. Anyway didn't think anything of it.

I pulled out of the servo and I couldn't get over 60km/h. I yelled and cursed and looked for an engine light but nothing. Didn't help that i was running late for an important meeting and had about an hour and a half drive to get there. Still didn't connect the brake controller to this issue so drive a few km's home to change cars.

Anyway while pulling gear out of the 2014 D40 and placing it into the ever faithful Ford Courier I noticed the brake lights were still on. It was then it clicked. I had a look at the brake controller and wiggled the wires going into the rear of it. The LED display flashed back to 00 then blank. I fired up the rig and had full power again.

Can high temps effect electronics. It was 38 here today with the next 7 days straight to have a maximums between 42 to 37 degrees.

I think since the controller came on the vehicle when i purchased it and I only have an un-braked camper trailer I might remove it all together to stop the problem.

Thoughts?

 

[bods]

You could remove it if you wanted to. If you want to leave it there just in case, you can just unplug the wiring loom from the back and tuck it away somewhere.

High temps could affect them I guess. With electronics anything is possible...