It sounds like the converter box may have shorted out, which can cause high and low voltage readings. To verify this, you will want to test the power going into and out of the converter box. If all power readings are fine going into the box but not coming out of the converter, then we'll know it is a problem with the box and not an issue with your Lexus. I've provided a link to our article on troubleshooting 4 & 5-way wiring installations which may be helpful.
It is most likely a short... view full answer...
The P3 brake controller # 90195 only uses the 4 wires. The 5th wire you are referring to sounds like the illumination circuit that is not needed by the brake controller. I am not sure though what the year, make, and model of your vehicle is.
You should get the no trailer connected message with no trailer connected when you apply the manual override but not with the brake pedal. Brake controllers like the P3 need to be moving (the vehicle moving with the brake controller in it I mean) so... view full answer...
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