SC430 gone for a burton, me thinks

HoniaraKid · April 10

Greetings All,

Friend trying to assist a friend. 2009 SC430 30k. The car is only used between April and September. Hold your stomachs in this is hilarious. Owners tried to jump start the car THREE times with reverse polarity!!!!!!!!!!. Neighbour said he could see arc light from over the road. I get there and find the Battery has no voltage at all. Literally 0.2v. Positive terminal has MOVED about 3mm in casing. New Battery fitted with 50w in series as choke. Only door lights, door open light on dash and headlights work. No comms on OBD. 50w bulb removed, no change. 140A main ALT fuse destroyed. When bridged and current monitored with amp clamp, rad fan spins up immediately to full power. Other various underbonnet items come online. Dash lights come on, dial backlighting etc. Crank no start. Power windows, locks remote unlock etc offline. No other fuses I can see are blown. No comms on OBD. Only had 15mins on this visit. Anyone been here before? Suspicious of Gateway Module onwards now unless I am missing other fuses. Reverse polarity is no joke so reckon ECU's died before 140A blew up. Laughter on a postcard please. Thanks

Nigel Coleman · April 12

I would think there are plenty of used ECU's for pre-facelift models from breakers but might be harder to find for a 2009?

It also depends on which one - if any - is blown ?

Jon Dee · April 12

I'm wondering if by any chance the main ECU has reverse polarity protection. I was doing a bit of bench programming once on an aftermarket ECU using a 12V car Battery as a power supply. I inadvertently got the leads crossed and BAM !!! Instant smoke as the insulation on my skinny test leads melted. On investigation it turned out that there was a sacrificial diode inside the box connected across the power supply. I had that replaced and the ECU was unharmed.

Might be worth opening the ECU or at least testing it to see if it has a power supply to ground short circuit. I'd guess that reversed polarity in cars is a known hazard and the manufacturers might have provided some protection.

Cheers...

HoniaraKid · April 12

Thank you for that headsup @Jon Dee That will be added to my list. Cheers

steve2006 · April 12

Firstly what was the current draw shown on the clamp meter?
With that amount of current and reversed polarity we are looking at open circuits rather then short circuits, the ECU may have protection but this is generally just a series diode which would have been easily overcome by the current.

When you say “no other fuses I can see are blown” there are 4 fuse boxes in this car all of which need checking with a multimeter.

You will also need a power distribution diagram showing what goes to which fuse and where from there.

The video below is just the beginning of the diagnosis I’m afraid and a factory Electrical workshop manual another on the list.

Bob King · April 13

Posted this on the wrong thread the other day 🙄

yes American spec but will help you find all the fuse locations…

https://youtu.be/xB5IkXcUMvA?si=YCzD_KbXrk5UDUNx

HoniaraKid · April 13

Thank you very much. Current draw was high when the Battery was first renewed and the 140A fused bridged as the radiator or condensor fan was running flatout. I am going to look again at the car soon when Lexus deliver the new 140A fuse. I shall be back.

HoniaraKid · April 21

Gentlemen, the risk or using brute force and or C4 grows by the minute. How in the name of flying chimps does the top part of the narrow fuse box come off? I have undone the 10mm on the main feed. I have trying feelker guages, screwdrivers etc in each of the four clips and prising upwards. Nothing budges. I have looked on YT but not found anything remotely useful. Can anyone assist please. Sanity on hold for now. Cheers

Malc1 · April 21

Have you got a handy 7 year old child to guide you thru’ this impossible maze ?
……. Might need the simple touch 🤔

Malc

steve2006 · April 21

It’s not fun I’ve done one!
OK google “Lexus Main fuse replacement”

Then click on “videos”

These will show you what to do.

Make sure the Battery is disconnected first.

Bob King · April 21

Think once you know they bolt in, one won’t destroy the fuse box like in the link above !

This maybe some help…..

https://www.clublexus.com/forums/performance-and-maintenance/494068-diy-alternator-fuse.html

steve2006 · April 21

Oh crap! I didn’t watch it all, I’ve now hidden it, always watch the complete video.

Neil E · April 21

I've only done it once and it was very tricky.

Try this

Bob King · April 21

3 hours ago, steve2006 said:

Oh crap! I didn’t watch it all, I’ve now hidden it, always watch the complete video.

Looked like his Rockweiler had taken the fuse box apart 😁

HoniaraKid · April 21

Thank you to @Malc1 I am still laughing.

I have managed to remove it. A very poor design. When you look at it, it appears to come out from the top, but it does for those that know come up and bit then the base slides out after being unscrewed. It was clips of stupidity that are so annoying. Anyway the 140A is replaced but the car is still dead as expected. Got Disco 5 to service tomorrow then I will go back and check all the relevant fuses. I have the list from the link above so thank you for that. The fuses block under the glovebox smells a bit so it will need to come out to see if its been damaged. I still cant read the VIN so comms are still done. I know there is an OBD fuse which I will be check. I have an 220w dummy load in series with the Battery just to make sure that car doesnt try to take more than 18A without me noticing, during testing. I have the rad fan disconnected as that is running continously currently. I had noticed the power window fuse (41) is open circuit, so I replaced that and the windows came backs online and keyfob is dead so I have a 1616 coming for that. The locks are still offline from the key barrel but do work from the lock inside on the door. Seems odd, but I see there is another fuse associated with that circuit.

More when I look tomorrow. Thank you for the video @Neil E it is similar but the four main clips were holding on for life. It doesnt help that the loom has no slack.

Anyway thanks everyone.

Just download for $20 the entire wiring schematic for the 2010 SC430. Here is the power section if anyone wants it.

Malc1 · April 21

Chill out and Sleep on it …… might make a difference in the morning with a fresh mind and eyes

Malc

HoniaraKid · April 25

The car is now running. It does however have a misfire and one AVC/LAN bus is down. All systems are up, except the radio. I will do a more comprehensive report soon. Apart from the new Battery and the 140A fuse, there were nine other fuses and arc damage to one the ECU plugs. One pin to be precises must have been hit with a fair bit of current. When I took the ECU out I could smell it. I am going to scope the coil triggers to see if the misfire is a FET issue or loom/coil coincidence. I do not believe the monster reverse surge would have gone through the ECU to a coil without killing the ECU forst. On inspection it looks fine inside. Anyway I have been documenting my finds so I will publish soon.

HoniaraKid · April 26

Spectacular piece of coincidence. The misfire was down to coil plug being adrift on coil 3. I am saying three - left bank 3 in facing the windscreen. Car was serviced about two months ago. So no ECU worries. 🙂 Interestingly now the radio is working the error for the AVC/LAN bus has gone. So without research I can only guess it has something to do with the Mark Levinson system bus. It has a Pionner headunit installed that I fitted about 2 years ago, but that uses a Lexus data converter so the Levinson system works as it should including the steering wheel buttons. Had a A/C DTC, that was logged as Historic but didnt show last scan. Also had two DTC for the oleft and right Solar sensors. Hardly surprising with the car in agarage 8 months of the year. Just taken it for the final test drive before handover and the Solar Sensor DTC has gone and taken the AC fault with it, so happy days. Will let owner use it for a week then plug in again and see if anything has occured. More info on the fault finding later. Thank you to everyone.

Jon Dee · April 26

Well done !!! Always a pleasure to read about the work of someone who actually knows what they are doing to diagnose and solve electrical dramas on CANbus cars 👍👍