OG Dada

iTrader: (10)

My 1995 SC400 is still giving me problems and I'm getting tired of it, seriously. I was planning on selling it quick after getting the 5 speed, but want to fix the problems I'm having with it first to get top dollar since its a high mileage. What's happening is it keeps on unlocking itself without any warning or any reason at all without pressing the unlock button on the switch or the key FOB, and it happens even when I'm driving. And the lock button on either the switch or the key FOB will no longer work after all this happens, so I need to manually press the locks, until it happens again after a while. What''s really pissing me off is there are times that when I walk up to the car the next morning it's already unlocked.

Here are things I've already done before the problem occurred. About 2 years ago, my window stopped working while I was driving. It was just stuck in the open position and I couldn't close it without helping the motor push it up. So, to try and fix it, someone suggested replacing the ground wire, it's the color white with a black stripe on it, and a little bit thicker than the other wires. I replaced the wire from the plug of the switch, then tapped it in to a good ground on the door, which someone also suggested worked for him and so I did. It did not fix the window problem though, later on it turned out to be just the window motor needing to be cleaned due to carbon build up inside the motor. The locks and alarm worked fine for the past 2 years like that, with only one side effect. Whenever I would shut the door it would unlock twice. Didn't bother me much since it didn't make any difference to the functionalities of the alarm nor the locks.

I only had the key without the button when I got my SC, so I had to manually open the locks every time back then. I grew tired of it and eventually bought a brand new key FOB from Lexus Sewell. I got it programmed to the car with the instructions I found here in CL, and it worked perfectly fine for about a year or so. Then this problem started. Last night I replaced the ground wire again, but this time I put it back the way it is supposed to be. I rewired from the switch to the fuse box in the foot panel. It still does the same thing. Unlocks itself with no warning, but not as much as before, where sometimes it almost wouldn't stop. But I noticed that the lock function only works when the key is in the ignition. When it's out, it doesn't work at all. I tried using the switch from my other SC, which works perfectly fine, and still the same, so I know its not the switch. Anybody help?

TheAzn

iTrader: (2)

Could be the Door Lock Control/ Theft Deterent ECU.

I've been having my factory alarm sounding for no reason. I had my dashcam run one time when I locked and left the car. Caught on camera It sounded like my car re-locked itself and triggered the alarm on its own...

t2d2

iTrader: (8)

Have you tried taking the battery out of the FOB to see if it's sending an errant signal? Probably not the case, if it's unlocking itself overnight, but it would eliminate one of the easiest things to check.

soarer93

I suggest - opening the door(s) and noticing the exposed wiring where the rubber boot should be protecting it from water -
Usually happened to my car after pressure washing it - ensuring water got in there, or after a long heavy rain - that being said.. I just ended up pushing the boot more intowards the door to better cover the wires - and havnt had that issue since.. Though best option is to replace that boot, or silicone it up or something..
though mine would actually LOCK instead of Unlock.

OG Dada

iTrader: (10)

Hmmm... So yours locks instead of unlocking... I read somewhere here in the past that our electrical have a common ground for each electronic part. I don't know if I messed it up when I grounded it on the door that's why it immediately had that effect where it unlocks twice everytime I shut the door. It's just weird that it developed that intermittent unlocking in time and not immediately like the fore mentioned.

soarer93

Im still betting its moisture in the wiring -

OG Dada

iTrader: (10)

It got me really thinking, cause one thing I noticed ever since this problem started, is it only happens when the weather is cold. When it's really hot it never malfunctions like that. I'll open it up and take a look. I know for sure that there's a rip in the rubber loom. I did read somewhere here that there are wires that do get cut from there so I'll take a look. Thanks for the input. I'll report back whatever happens.

OG Dada

iTrader: (10)

ISSUE FIXED!!!

Kris9884

iTrader: (7)

Was is the wire/looming in the door?

OG Dada

iTrader: (10)

Nope. It's in the wiring harness leading to the o2 sensor. Click on it to see the pics I from the other thread.

Kris9884

iTrader: (7)

Oh lol, the blue text color made it look like it was just bold, didn't even think to click on it. Awesome fix, I would never have thought to go under the car for this issue... Crazy..

t2d2

iTrader: (8)

Those were some gnarly looking wires! I've found two partially bare wires in my engine bay, worn out from where they bend toward the connector, but nothing nearly as bad as your's. And mine were only one bare wire per connector, so not a bunch of adjacent bare wires touching each other.

94sctt

iTrader: (1)

I clicked on the ISSUE FIXED but didn't see the pictures.

94sctt

iTrader: (1)

Never mind. Didn't think to check the other pages on the thread.

OG Dada

iTrader: (10)

I wouldn't have guessed it in a million years. But I guess this is where "the central grounding for each electronic part takes place" if that affected the alarm as well.

Yeah, the previous owner had a really bad oil leak going on before I got the SC. I fixed it, then a couple years later another oil leak came out. I've seen a lot of wire insulations frayed just like this due to years of being soaked in oil then the engine constantly heating it up. The insulation becomes really brittle and just chips off when rubbing against each other.