93 Grand Cherokee - Towing Brake light problem

[FrostyTech]

Greetings,
My 93 Jeep Grand Cherokee (I6 - AWD) is having a problem with the rear towing brake and turn lights..

Towing Parking lights work fine.
Turn headlights on, parking lights turn on, including the trailer.

It's the brake and turn light voltage from the Jeep.
I'm using the adapter that converts the round cable connector to the standard 4 pin flat trailer connector

No voltage on pins 3 and 4 from the Jeep
(1-ground, 2-parking, 3 and 4 - brake and L/R turn lights)

I know the cable connector and converter is fine.
Tore it apart, cleaned it out, checked wires..

I know the trailer lights on the trailer (parking, brake, and turning) work fine.

The problem appears to be NO voltage comes from the Jeep to the trailer for the brake or turn signals.. (pins 3 and 4)

I am 100% sure the problem is the wiring on the Jeep before the actually towing lights cable connector..

All Fuses are good.

Anybody have some suggestions where to start checking?

I'm fairly adept at troubleshooting electrical circuits..
I simply cannot locate where the trailer towing cable gut ties back into the actual wiring on the Jeep. It goes into the frame on the passenger rear and I cannot figure out where it goes from there.

I'll be unavailable to reply for the next 3 hours, but I will return to check for responses and to carry on the conversation..

Thanks!!!

[Mord]

According to my diagrams, the main connectors are at the right rear quarter panel and under the rear seat.

1 question: if pins 3 and 4 are for brake and turning, assuming pin 3 is for brake signal, when it gets voltage on pin 4 for turning, how does the trailer know if its turning left or right?

[FrostyTech]

Pin 3 and 4: dual action
3 and 4 constant voltage = brake lights
3 or 4 on/off voltage = turn signal (same light as brake)

I've checked the rear panel and connectors under back seat.
The cable / connectors under the back seat make no difference.
I disconnected the plug and brake lights on the Jeep stayed on.
In the rear quarter panel, it's the 'light failure' detection electronics.

I believe the trailer towing wire gut ties in under the dash.
I'm not positive, but I'm waiting for a buddy who's a Jeep expert to reply to an email.

[treker]

Originally Posted by FrostyTech

Pin 3 and 4: dual action
3 and 4 constant voltage = brake lights
3 or 4 on/off voltage = turn signal (same light as brake)

I've checked the rear panel and connectors under back seat.
The cable / connectors under the back seat make no difference.
I disconnected the plug and brake lights on the Jeep stayed on.
In the rear quarter panel, it's the 'light failure' detection electronics.

I believe the trailer towing wire gut ties in under the dash.
I'm not positive, but I'm waiting for a buddy who's a Jeep expert to reply to an email.

I have 96 GC with same problem. I have not had time to look into it so any help would be nice. Thanks