Surge Trailer Brakes Lock Up when Backing Up on Trailer with Electric Reverse Lockout  

Question:

Expert Reply:

If your 2006 Toyota 4Runner has a 7-Way, then the center pin on it should be the reverse light circuit. To test it you will need one other person, a circuit tester such as # PTW2993, and the vehicle wheels will need to be chocked. Basically, you will have the other person sit in the vehicle, start it up, apply the emergency brake, keep their foot on the brake, and put the vehicle in reverse while the wheels are chocked (safety first). Then you can use the circuit tester to test that center pin on the 7-Way.

If there is no power when doing this test, then it could be a blown fuse or relay on the vehicle side. If there is power, then the issue is somewhere else.

I assume you are using a 7-Way to 5-Way adapter such as # A75TB. You can perform the same test as above only this time with the adapter plugged in. The pin furthest from the uncovered ground pin should have power then the vehicle is in reverse. If the 7-Way does but the adapter does not (show power) then there is something wrong with the adapter and it will need to be replaced.

If everything on the vehicle side is working fine, then the issue is on the trailer side. Check to make sure that the last pin and its associated wire goes to the solenoid on the coupler and that the solenoid is grounded to a clean bare metal surface. If power is making it all the way to the solenoid when the vehicle is in reverse, but it isn't activating then there is something wrong with the solenoid and it will need to be replaced.

There are different kinds of reverse lockout solenoids. One type when powered will route brake fluid back into the master cylinder so there will be a separate line that feeds back into the master cylinder like in # DM5404. The other type is just in line with the brake line and does not feed back into the master cylinder, # DM11993.

expert reply by: Michael H

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