1991 Ls-400 Electrical Problem

[David E]

I have a 1991 LS-400. My dash shows a light out, but all lights are working. When I hit the brake the "R" (reverse) light comes on. Suddenly, when my lights are on, the transmission will not shift out of 1st gear (this is an automatic). If I turn off the lights, the transmission is fine. Any thoughts if the two problems are related and what the fix would be?

[steve2006]

I have a 1991 LS-400. My dash shows a light out, but all lights are working. When I hit the brake the "R" (reverse) light comes on. Suddenly, when my lights are on, the transmission will not shift out of 1st gear (this is an automatic). If I turn off the lights, the transmission is fine. Any thoughts if the two problems are related and what the fix would be?

Hi,

This sounds like the usual LS problem due to a break in the wiring loom that passes over the trunk lid hinge.

If you look on top of the hinge on the LHS ( may be the RHS in the US) you will see a loom covered in plastic that contains the wires to the trunk lid lights.

Carefully open this up and check for frayed/broken wires.

Repair as needed and this should sort your problem.