when in gear and apply brake, reverse light illuminates & engine is strained

20

Asked by Jul 25, 2012 at 02:17 PM about the 1992 Lexus LS 400 RWD

Question type: Maintenance & Repair

when I put the car in drive and come to a stop, the moment I press on the brake petal both the drive and reverse
lights are illuminated on the dash and the car engine seems to be downshifting into 2nd but the rpms are
increasing...like the engine is fighting itself

7 Answers

55

kind of sounds like a brake light switch shorting out or possibly a sensor on the transmission.

2 of 2 people found this helpful.
20

we thought this too but even when we disconnect the brake lights on both sides at the same time, the problem continues but erratically where when the brake lights are connected it happens each time the brake is pressed. friend/mechanic is going to override the park release button to see if that helps any but i will advise him to look for a sensor on the tranny....thank you

20

ok both brake/tail lights are off of the car and the braking switch is disconnected & the gear lock is disengaged and yet the reverse light still comes on when the brakes are applied; however, the engine does not seem to be downshifting or increasing rpm as before. tomorrow friend is going to disconnect the 3rd brake light and the cruise control. any other ideas as then we'll start to trace the turn signals? any idea where the sensor on the transmission might be....internal or external? thank you

2 of 2 people found this helpful.
30

i had this prob. we looked everywhere. it was really simple though. the wire from the brakes from the trunk were loose. the wires are located within the trunk and the opening and closing cut the wire in such a way where it would shift it into reverse for a fraction of a second. fix/change the wires located in the boot and ull be good to go.

3 of 3 people found this helpful.
20

Du, you were right. the white wire with a blue tracer was the problem but there is more. mine was broke in 2 places. So pull all to the black tape off and the all the wires. the green ones looked in rough shape too! also had a left front fog light bulb being replaced every two weeks, had a bad right rear brake light socket go bad, replaced the harness (factory) and no more fog light bulb replacement. Bill

2 of 2 people found this helpful.
30

That's not too bad. That's really the only problem you'll have. Around 180k-200k, you'll need a new head gasket, but that's it. It's one of the best cars and put all the previous Mercs to shame.

10

Great to find this thread, A few days back, the tail light indicator was on. The then next day it was off. Today I noticed that the door ajar light was on. As I was slowing for a stop sign, there was a sudden shudder as if I had jammed the brake. Once again as I was coming to a stop and this time I noticed the Reverse indicator came on as soon as I touched the brake. Got home and did a google and the first hit was this thread. Popped the trunk and noticed a wire hangin on the left trunk hinge as I was looking in the trunk. Pealed back the tape and there was the break in the "White Wire with dark tracer" I didn't have any but splices in my stock, so down to the hardware to pick up a package. Spliced the broken wire and did a road test and all is well again. From the time I first popped the trunk to have a look to finish taping the harness back together and putting things right, about 20 minutes and 15 of that was the trip to the hardware store. Can't thank you guys enough.

1 of 1 people found this helpful.

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