TyStephens

Hey everyone,

I've been searching around and no one seems to have mentioned this issue before so I thought I would start a thread based off what I'm about to go through lol

I have a 1996 Lexus SC400 with 265,xxx KM on it, nearly 100,000 put on by yours truly. One morning on my way to work the car started acting strange. When I would press the brake pedal any amount (light or heavy braking) the transmission would downshift, rpm would spike up then once the pedal was released it shifts back.

Symptoms are as followed
If left in Drive with Overdrive OFF, the car shifts and brakes normally, once you turn it on and touch the brakes it starts downshifting on me.
Reverse seems to be unaffected.
Shifting from 1st - 2nd - Drive goes fine, but really rough shifts Drive- 2nd - 1st
Occasionally lurches forward when put into Drive (however this has been the case since tightening up the throttle cable over a year ago)

A CEL has come on for P1780 PNP Sensor Malfunction and will not go away with clearing the code
My car does have the "4th Solenoid mod" set on a relay and switch. It's been used maybe 20 times, last time being over a year ago and sits in the normal functioning position


I found a PNP Sensor (neutral safety switch) from a 92 but of course after an hour getting the other one off, it has a different plug.
Does anyone have an incite as to what to look for while I search for another PNP Sensor?


Thanks in advance!


Pic of my bae

TyStephens

** SOLVED**

Well I dug around on the interwebs and found a guy with a Corolla who had the same code but not the same symptoms. His issue was that he had a broken taillight wire throwing that code, thats when the bells started ringing!
I had installed an LED Strip on my sunroof 3 years ago, and wired it into my taillights. Just recently someone pointed out that it wasnt working anymore and I thought nothing of it, sure enough I unplug the wires for that extra brake light, clear the CEL code and it shifts normally!!!!
What a strange seemingly unrelated issue to cause this but thats why people hate electrical issues I guess lol

Maserati

iTrader: (1)

Hmm, Thats pretty interesting. I want t o do the led strip break light mod also. Hopefully this doesn't happen. Thanks for your findings!