Check engine with trailer connected

[Ivan Tuma]

the question is ... does the "brake problem" light come on or the "brake 
lamp" light come on.
my understanding is that the lighting system test the entire system for 
a certain resistance ... when
adding another set of brake lights in parallel on the trailer, you in 
effect reduce the resistance in
the brake light circuitry thereby causing the warning system to think a 
brake light is out.


Larry Newman wrote:

> I recently installed a trailer hitch and wired my '89 200 for a 6 wire
> trailer umbilical.  Whenever I connect the plug to the trailer, my Check
> Engine light comes on and indicates a brake malfunction.  I've been told
> by an Audi owner who tows a race car that this always happens and there
> is nothing one do about it.  Anybody familiar with this phenomenom and
> have discovered a way to have the trailer connected without lighting up
> the brake problem symbol?
> 
> Larry
> 
> 
>