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Dash Lights Dim When Brakes Applied!


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SOP, sort of.........

Clean and burnish the battery terminals and connectors will help somewhat.

When engine falls to idle, and rear brake lights add to load, alternator doesn't pick up the load right away so battery must fill in. Unless the battery can't turn the engine over for starting everything electrical is SOP.

On newer models Lexus disables the torque converter lockup the instant you touch the brake. But then that should "feel" like an upshift.

Don't

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  • 4 months later...
Hey guy's,

Check this out...my dash lights dim and the transmission downshifts everytime I touch the brakes on my 91 ls.  It sounds like it would be a sensor or something like that.  Any suggestions?  Please help.

check the posts, but there is a wire bundle on the drivers side trunk hinge that flexes and breaks. this cause your reverse indicator to light up when the brake is applied and also feels like the transmission is disconecting or downshifting. Fix that wire, and your car will not jerk anymore when touching the brake. For some reason this fixes a lot of problems. I fixed mine, with butt connector, but im sure that soldering the wire back would be cool too. later

THE SNAKE

1992 LS 400

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  • 3 weeks later...
Hey guy's,

Check this out...my dash lights dim and the transmission downshifts everytime I touch the brakes on my 91 ls.  It sounds like it would be a sensor or something like that.  Any suggestions?  Please help.

check the posts, but there is a wire bundle on the drivers side trunk hinge that flexes and breaks. this cause your reverse indicator to light up when the brake is applied and also feels like the transmission is disconecting or downshifting. Fix that wire, and your car will not jerk anymore when touching the brake. For some reason this fixes a lot of problems. I fixed mine, with butt connector, but im sure that soldering the wire back would be cool too. later

THE SNAKE

1992 LS 400

Thanks Man! Cleaned the battery connectors well. Still didn't help.

After more investigation, it seems to downshift from OD to 3rd (or D) once the brake is applied, however, if I take it out of OD and place it in D and apply the brake it stays in that gear when the brake is applied.

Suggestions!

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check the forum for posts related to this, i did,...... but there is a wire bundle on the drivers side trunk hinge that flexes and breaks one of the wires in this bundle. . this broken wire causes your reverse indicator to light up when the brake is applied and also feels like the transmission is disconecting or downshifting. Fix that wire, and your car will not jerk anymore when touching the brake. For some reason this fixes a lot of problems. I fixed mine, with a butt connector, but im sure that soldering the wire back would be cool too. later

THE SNAKE

1992 LS 400

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  • 3 months later...

Checked the white w/black strip wire on left side of trunk hinge and it was cut. Spliced it back together as you suggested and it fixed everything! WOW! Thanks!

You the MAN!

SOP, sort of.........

Clean and burnish the battery terminals and connectors will help somewhat.

When engine falls to idle, and rear brake lights add to load, alternator doesn't pick up the load right away so battery must fill in. Unless the battery can't turn the engine over for starting everything electrical is SOP.

On newer models Lexus disables the torque converter lockup the instant you touch the brake. But then that should "feel" like an upshift.

Don't

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SOP, sort of.........

Clean and burnish the battery terminals and connectors will help somewhat.

When engine falls to idle, and rear brake lights add to load, alternator doesn't pick up the load right away so battery must fill in. Unless the battery can't turn the engine over for starting everything electrical is SOP.

On newer models Lexus disables the torque converter lockup the instant you touch the brake. But then that should "feel" like an upshift.

Don't

for you no military types, SOP= Standard Operating Procedure. :D

EDIT: aw hell, he solved the problem...im late again! :(

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check the posts, but there is a wire bundle on the drivers side trunk hinge that flexes and breaks. this cause your reverse indicator to light up when the brake is applied and also feels like the transmission is disconecting or downshifting. Fix that wire, and your car will not jerk anymore when touching the brake. For some reason this fixes a lot of problems. I fixed mine, with butt connector, but im sure that soldering the wire back would be cool too. later

THE SNAKE

1992 LS 400

I wouldn't have believed it, but I found that the wire at the hinge was cracked. My garage fixed it and the problem went away. One garage was going to charge $$$$ to fix the problem by going into the transmission. My garage charged me $96 and this included an A/C service as well. A million thanks to the SNAKE 8^)

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  • 6 years later...

Hi, I am new to this forum and I'm experiencing the same problems with my 98 GS300. May someone please provide me with feedback as to what wire you're referring to so I could resolve this issue with the dash lights dimming while pressing the brake pedal. Thank you for your time and attention.

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This trunk wiring issue only applies to 90-94 LS's.

I would carefully check your ground connections to the chassis from the battery to see if there might be some corrosion. Do any other interior lights dim or just the dash lights?

Also, this is the LS forum, not the GS. You might have someone who knows on that side.

Welcome, Michael.

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