I made a thread a few weeks ago when my car all of a sudden died. To get straight to the point, I took my battery to get replaced and it turned out the old one had a bad cell. I was hoping it was the battery that was the issue but I put it in my car and it still doesn't start.
All of my electronics and lights work as if the car was running. A few times throughout the last year my car would not start at first, so I would try again. Sometimes it would start right away, and other times it was rather weak but would start. I think most of the time when the car wouldn't start, my clock would reset, as if my battery was disconnected. I've never had my car stall out or any issues while actually driving it besides a "hiccup" or "pop" where it feels like the car hiccups. But from some reading it could be related to the IACV??. Anyways I'm really hoping my starter isn't the culprit because I have no time and no space to work on it. I wouldn't even be able to get the car in my garage because my drive way is at probably a 15-20 degree angle.

Here is what I've tried so far:
- Replaced battery and made sure cables were tight on the terminals
- Checked the fuses in the engine bay fusebox as well as the footwell, everything appeared fine
- Checked the only ground I could find for the negative terminal (near the oil filter). I checked to see if it was tightened (it was tight) and cleaned the gunk off it
- Tried jumping the 3 and 5 on the relay plug in the fuse box
- Tried doing the fuel pump bypass in the diagnostic port on the intake manifold
- Made sure car was in park and made sure the corresponding light on the dash was on "P"
- Tried starting it in neutral
- Opened the car as if the security alarm went off
- Checked to see if the starter relay clicks and it does.

So far nothing has worked. I only found one ground location for the negative cable. I found one diagram but I couldn't for the life of me find exact locations. Right now the car does not click or anything. When I turn the key to start it it just dies and the lights dim.
Does it sound like a grounding issue? Could I have fried my computer if I tried starting it too much or with a dead battery? I did smell burning once but it looked like it was mostly at the battery terminals. I also read in some threads it could be the fuel pump? But like I said earlier I've never had issues while actually driving the car. I'm not too knowledgeable and at this point I think I've tried basically everything that doesn't require taking the engine apart. What are some other things I can check? I think I pretty did everything on the list from https://www.lextreme.com/how-to-diag...aulty-starter/

If anyone has any insight, I would really appreciate it. I'm not sure what to do besides take it to the mechanic.

 

Is your car an automatic? Maybe the neutral safety start switch is failing. You need to do some basic diagnostics, first find out if the starter relay is working, then look for power output on the relay and trace it as close as possible to the starter solenoid. What is the battery voltage when you try to crank the engine? Is there a voltage drop between the battery post and the battery terminal when trying to crank the engine?

 

It's an automatic. Relay is working, clicks when trying to start the car. My dad took my multi meter to his house so I can't test the voltage right now. The solenoid is basically in the same area as the starter itself right? I do hear a sound within the intake manifold as well. I'm not really sure what the starter trying to run sounds like. I'm pretty ignorant when it comes to most things electrical. I'll see if he can find it so I can test the voltage. So when I want to test the voltage, I know the settings to put it on, but where exactly would I put the leads in this case? Or is there a guide? Thank you for the help!

And just to add, I could not find any records from the previous owner about starter replacement, so I'm guessing they never replaced it? OR if they did they didn't keep the receipt or paperwork. Also my car has around 230-240K miles I believe. Just thought I'd add that.

 

IACV doesn't sound likely. Starter is always a concern... They don't fail often (yours is most likely the original), but they're a major project when they do.

I'm with Lexus2000 on the starter relay. I had a brief stretch of odd behavior that went away when I swapped in a replacement, despite nothing appearing wrong with the original. It's in the fuse box in the engine bay and is the purple one, if I remember correctly.

Another possibility is ECU. Leaking capacitors are known to cause all sorts of problems, so if you have no records of yours having been serviced, consider that something that needs looking into regardless.

 

I thought the starter relay was the green one. I believe I do have a purple relay in there too. The ECU is the one in the rear driver side quarter panel right? How would I go about checking that? If I tried jumping 3 and 5 positions in the starter relay plug holes and it didn't start, would that not mean the starter is dead? Should I try another starter relay?

 

That's the fuel pump ECU back there. The main ECU is in the passenger foot well, below a plastic cover where you put your feet. All you can do to check it is open it up and look for capacitor leakage, damage to the board, etc. However, my old one was nealry toast and I couldn't tell from looking at it, because the damage was mostly hidden from view.

 

So I finally got the time to take the ECU out and open it. I took pictures of the capacitors but I did not see any leaking or blown caps in there. I didn't see any damage to the board itself either. Honestly the thing looks brand new.
So since the ECU seems to be in good shape, would the most likely culprit be the starter? I haven't tested the voltage but I did find out my battery had a bad cell so I replaced it hoping that was the issue. Unfortunately it doesn't even click more than once anymore. Now it just clicks once and dies. When I try to start the car it clicks and then the dash dims and the lights pretty much turn off in the car. Any other thoughts or suggestions? I really don't have time or the space to replace the starter, so if it does end being that I would probably get some estimates at local mechanics. And if I do end up taking it to someone local, it's recommended to change the TB and water pump right?
Also I read in some threads to check to see if the fuel pump turns on? I'm pretty dumb when it comes to this kind of thing, but I would have to turn the key to "on" in order for the pump to actually turn on? Do you think it sounds like a failing fuel pump or fuel pump ECU?

Thanks a lot for your help!

 

That doesn't sound like the starter to me. A bad starter wouldn't cause all the lights to go out like that unless the battery was also flat, but you just put a fresh one in and haven't been able to put a load on it without any cranking. Seems like an electrical problem, maybe as simple as a bad ground somewhere. I still say, try out another starter relay before messing with anything else.

 

So I bought a new relay from Autozone (https://www.autozone.com/batteries-s...133/221834_0_0) and the car still does the same exact thing.
What I did notice when I try the fuel pump bypass in the diagnostic port in the engine bay is that I hear a whirring sound in the backseat area which I'm guessing is the fuel pump working? If I'm not doing the fuel pump bypass then all I hear is a thud-like sound when I turn the key to try and start the car. One thing I do remember is ever since I replaced my rear passenger tail light, I had the rear light warning turn on on my dash. Could that have done anything? About the ground locations, I only found the one near the oil filter, I think one on the driver side near the valve cover, and then the one near the back of the engine that goes to the firewall. I couldn't really find a post on here or anywhere where they show the locations with photos. I found a diagram on a Soarer website (http://soarercentral.com/sc-forum/me...51/103160.html) but it didn't really help me as I'm still learning. I tried to make an account on the website to ask a question but it is region locked.I also found a diagram, it might have been the manual but I'm not 100% sure. But it was still difficult for me to understand. From what I read they say to follow the negative cable, but I only got to the one near the oil filter and then the cable goes too far for me to follow. I read there was one on the intake manifold but I could not find it. They say a loose bolt could be causing a short but the grounds that I did find were tight. I also cleaned them with some degreaser.

Here is a video I just took showing what happens and a picture of my dash:

 

Yeah, the fuel pump makes an audible whirring noise when the engine isn't running to drown it out. Sounds like your fuel pump ecu is dead, but that's a separate issue.

I don't see what replacing the tail light would have to do with the symptoms... Weird that it triggered the dash warning light, though. I assume you replaced it with the correct sub-generation ('92-94, '95-96, '97-00)? If so, I suppose it's possible the wiring got damaged in removing the old one. Did you reuse your old tail light harness (i.e., leave it plugged in and just take the bulbs out of the old housing) or did you use the one hooked to the replacement? If all you did was swap the bulbs to the new housing, I don't see how that could have done anything. If you swapped harnesses, there could be a short or something in the new one.

Do you have a battery analyzer to double check that it hasn't gone flat during all the troubleshooting? That would be worth crossing off the list. Lug it to an auto parts store if not.

 

Yeah now that I think about idk what the issue could be with that. I used the original harness and bulbs. My old one was cracked and had moisture in it. This new one is exactly the same, I'm not sure the year but it's definitely the older style. That was the only thing I could think of about the dash light. I did put in some LED headlights and brights but the dash light had been on and off before this.
Do you think the fuel pump ecu could be my issue? I was wondering about that since I read in a various threads that it's pretty common and a lot of people do the 12v mod. When you watch my video, what do you think it sounds like? A short somewhere? I found this thread (https://www.clublexus.com/forums/sc-...e-diagram.html) and even though it's an SC300, would the grounding points be generally in the same area as in the SC400? The battery is barely 2 weeks old and the only thing I've tried to get the car to work is 1.) putting in the new battery 2.) trying to do fuel pump bypass 3.) new starter relay. Other than that I took out the ECU.
I'm trying to think of anything weird that happened the same day before it died. The only thing that happened a few times before that point was the car not starting on the first try. It would feel very weak and then start. And sometimes when I started the car I heard a metal grinding noise. Both of these issues would happen maybe 1-2 times once a month to every other month.

 

It does sort of sound like starter contacts. The other symptoms don't fit, though, so maybe you have multiple things going on. Hopefully others will chime in... Metal grinding noises are rarely a good thing.

As long as the fuel pump is running when you have its ecu temporarily bypassed, that wouldn't explain the issue.

I believe most of the grounds are the same between the 300 and 400.

Still, get that battery checked. It may not have been fresh on the shelf... (Did you check the date sticker?)

 

The battery was from last month when I bought it (8/19). I tested it and it's still good. Do you think it could be my EFI relay? I found another ground by the air intake but I'm not sure how it would short on anything. I do have a bolt that reaches near it but I can't see why it would mess up now. I'll have to go look again when it's light outside.
Also, do you know what this plugs into if anything? It's by the gas pedal. I just remembered earlier today that a year or two ago this wire would hang down by my feet. I just tucked it up in the footwell. I'm not sure how it would affect anything now but I'm curious if it goes anywhere. There was never an aftermarket headunit installed or new sound sysytem.

 

Any key fusing or relays are certainly suspect at this point.

I don't recognize that connector. It looks aftermarket.

 

I pulled the code for my CEL and it's giving me 12. I've read threads and other pages saying that 12 is RPM sensor, cam or crank sensors, or distributors. I also read in those threads that they tested for spark and fuel, but how would I do that? When I read these threads and videos talking about the distributor, do they mean the cap? Because when I google distributor for my SC400 I always get the caps. Do you think that could be the culprit?