I have a 2002 LS430 that won't start. Symptoms and diagnostics are odd:

- New battery, freshly charged
- No clicking sounds
- Getting all dash lights etc. turning on like normal
- Oddly, the cooling fan comes on when ignition turned to "on" position (though it's 35F in the garage)

Here's the mystery:
> I pulled the starter relay and checked for voltage at the terminals. Have no voltage to the starter feed terminal, and also no voltage at the relay actuation terminal when the ignition is turned to "start".
> The 7.5 amp fuse feeding the actuation side is good, as is the 30 amp fuse feeding the high-current side to the starter.
> There is voltage at the 30A fuse, but the odd thing is that I get no continuity detected between the other fuse terminal and the receiving contact on the relay. According to the wiring diagrams I have been able to find there is no component between these two points, and both are on the same fuseblock.

This situation plus the fan running make me wonder if perhaps there was a voltage spike that fried parts of the wiring and/or cpu.

Also, if anyone has a diagram with which I can confirm I'm checking the right relay, that would be helpful. What I've found has been less than clear; it seems to be #18 in the attached diagram. I also attached the schematic I'm using.

Any ideas?

Thanks very much!

 

Not sure how you're checking the voltage, for example, at the fuse. Fuses can be checked several ways.

One way is to pull the fuse out of the circuit, and check it for continuity. A good fuse will give you 0 OHMS. A blown fuse should give you OL on your multimeter when set to OHMS.

Another way to check the fuse is to leave the fuse IN the circuit/fuseholder/etc. If you use this method, then you should put the multimeter on DCV (or whatever the circuit's voltage is) and measure across the fuse. If the fuse is good, you should have 0 VDC across it. If the fuse is blown, you'll see 12DC or 24DC or whatever the circuit is, etc, across it.

Hopefully I'm not insulting your intelligence. I wasn't 100% understanding when you were reading voltage at the 30A fuse. Also, you really can't measure resistance (Ohms) on a live circuit. The circuit needs to be dead/no voltage in order for you to accurately measure continuity.

Not sure if this helps or not..but just throwing it out there.

 

Thanks for the reply. The fuse has continuity. But doesn't do any good because there is no voltage feeding it. Checked this by measuring between fuse terminal and ground. There should be voltage at one of the terminals, at least according to the wiring diagram.

 

Maybe your neutral switch is not closed (no clicking sounds at the starter relay). Try starting in N. If still not working move the shifter through gears and then test it in P and N.

 

Hope this helps...

 

Thanks, rkw77080! This diagram is different from the one I was using, which is attached in the original post. But I could not tell for sure if that one was for a 2002. Do you know that the one you provided is for a 2002? Very helpful.
And do you have a diagram of the fuseblock showing which relay is the starter relay? The diagram I was able to find was rather vague.
Thanks again!

 

No problem, here's a compilation of all power-related diagrams for the 2001-2003 LS430. Happy reading!

 

...and here's a spreadsheet with more details on what each fuse does...

 

Oh my gosh, RKW77080, those files are IMMENSELY helpful! Totally clears things up. I now know I'm testing the right relay, among other things. Also the wiring diagram I had been using was from the wrong year and was throwing me off. I had searched over an hour for better diagrams to no avail.

With the right circuit info, it now looks like my problem is the starter switch, not sending voltage up to the relay. I can now look into what it takes to fix that.

Meanwhile, I do have the cooling fan coming on with the starter switch on, but with these diagrams I can hopefully figure out why that is so.

Thanks again!
(And also thanks mrboca and others who chimed in!)

 

This may help...

 

EXACTLY what I needed! This is great. It's terrible trying to do diagnostics without schematics you can have confidence in. You saved me a lot of time and anxiety.
Thanks again.

 

hello all. anyone know the fix for this issue. it happen to my car last night

 

Bump... I've checked everything i know

 

Please provide more details. What are the symptoms, and what have you checked?

 

same symptoms as GARYC....I followed his steps hoping to find a blown fuse.

I have a 2002 LS430 that won't start. Symptoms and diagnostics are odd:

- New battery, freshly charged
- No clicking sounds
- Getting all dash lights etc. turning on like normal
- Oddly, the cooling fan comes on when ignition turned to "on" position

Here's the mystery:
> I pulled the starter relay and checked for voltage at the terminals. Have no voltage to the starter feed terminal, and also no voltage at the relay actuation terminal when the ignition is turned to "start".
> The 7.5 amp fuse feeding the actuation side is good, as is the 30 amp fuse feeding the high-current side to the starter.
> There is voltage at the 30A fuse, but the odd thing is that I get no continuity detected between the other fuse terminal and the receiving contact on the relay. According to the wiring diagrams I have been able to find there is no component between these two points, and both are on the same fuseblock.

This situation plus the fan running make me wonder if perhaps there was a voltage spike that fried parts of the wiring and/or cpu.

Also, if anyone has a diagram with which I can confirm I'm checking the right relay, that would be helpful. What I've found has been less than clear; it seems to be #18 in the attached diagram. I also attached the schematic I'm using.