Effduration

Here is the harness I made.
The wiring diagram I used.

The pink terminals are a temporary bypass till I have the original setup figured out.

Ouch...I am not sure I would have spliced the car side of that connector for your bypass- but it’s always reversible, I suppose.

I guess I cringe a little when I see spliced E53 wiring - which is my baggage.


That fact that you have created a bypass (which I presume works? ) from the car side of that connector tells me that the harness from that connector to the trailer plug (trailer side) is bad. I would pull your custom harness out and double check your wiring.

This is the controller I am using for now.

The vehicle side of the connector has the pink terminals.
I can re-attach the vehicle wires back to the vehicle plug, (That I did to check out that CURT 57003 LED-Compatible 7-Way) that is why I installed the pink terminals.

Those 3 pink terminals supply power (brake, L/R turn & park) through the vehicle plug into the trailer plug.(trailer Y,G & Br wire was only used to connect the Hopkins controller to those 3 terminals on the vehicle side)

I am a little puzzled. What does the Hopkins controller do? Trailer Brakes?

Curt 57003 is an adapter that plugs into your 7-way trailer plug (near the hitch). It required no splicing.

Trailer brakes are nice (if that's what the Hopkins controller is) but you should get it working as the manufacturer intended before adding trailer brakes.

All you needed was the white trailer module (which you show) and a proper harness between the in-car plug and the 7-way plug on the hitch outside. It was all plug and play. You don't need the hopkins controller in between.

They are not connected together at all.



I am a little puzzled. What does the Hopkins controller do? Trailer Brakes?

It's for vehicles equipped with independent bulb turn signals and brake signal or common bulb systems.

Curt 57003 is an adapter that plugs into your 7-way trailer plug (near the hitch). It required no splicing.

It hasn't been spliced.

Trailer brakes are nice (if that's what the Hopkins controller is) but you should get it working as the manufacturer intended before adding trailer brakes.

That is my intention.


All you needed was the white trailer module (which you show) and a proper harness between the in-car plug and the 7-way plug on the hitch outside. It was all plug and play. You don't need the hopkins controller in between.[/QUOTE]

They are not connected together at all.

Put it back to original. test the plug in the car.

-I suggest you connect the wiring as it was stock from the factory
-remove the hopkins controller
-make sure the OEM trailer module is installed near the battery cover and its wiring is stock

using a test light at the vehicle-side plug in the car, test the various functions.

If they don't work, you have a problem up the line (you have already tried 2 modules)

If they do work (and they should), you have a pblm with the harness between vehicle-side plug and trailer plug.

The images with my X5 and incandescent trailer, was with the OEM connected nothing else. And only mounted in the stock position/location.

(Only thing I made was the trailer plug to trailer connector. used OEM plug and pins that connect to vehicle plug, and used thicker wires.)

I had tested the Vehicle side plug wires with a voltmeter, I can read the bulb check pulsing on the voltmeter, but no turn/brake solid signal when initiated.

I will swap back the 3 pink terminals to the OEM setup, use a test light instead of the voltmeter. To verify I have a signal other than the pulses.
And post what I can back on this forum.

Here is the test.

Thanks for posting. Sorry to hear this. It appears the problem is upstream from that plug. I suppose you get the same issue with a different trailer module (you said you tried a different one earlier) ?

I really can't offer any more guidance remotely. Most of the time the factory wires/connectors for OEM trailer electronics are completely untouched and work perfectly. I would be looking for any other splices anywhere near the trailer module or rear light wiring. Any tail light error codes on the dash? If, for example, you had trouble with reverse lights, AND you had a back-up camera triggered by the reverse lights, I would be looking at that..But that doesn't seem to be the case here.

I had the Hopkins trailer controller hooked up before, it works fine. (use trailer frequently)
I wanted it to be a stock setup, (now have a bigger trailer, Car hauler with brakes) so to save money I purchased the module (real oem # match) of ebay.
Purchased the plug and pins and made the trailer harness.
Set everything up and got the same results.
Bought another module a year before mine, same outcome.
Hooked up bmw scanner, seen trailer light check box empty, I checked the box.
Plugged my new to me trailer and on the dash it displayed check trailer lights.
Tried park, turn & brake, and only the park lights worked.
Tried resistors (older post) , tried incandescent trailer and now a test light.
Same outcome.
Figured it might be coding (in the this forum someone mentioned "it's plug and play, rarely it might happen but it does, that it would need coding")

That being said, (having to use my trailer weekly) I installed those 3 pink terminals so I could continue using my trailer (Hopkins controller) without getting a ticket for the trailer lights. (brake controller not installed yet)

I appreciate your time and effort, in troubleshooting it with me.