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After diying so much on my beloved RX400H- new rad, o2 sensors, height adjuster, brakes. It was running so well. Just needed to upgrade the ancillary Battery.

Then I zap the fuses like a moron by reverse polarity. It was the end of a tiring day and I had rotated Battery and just messed up. 5 seconds of big sparks, headlights full on. Idiot. 

Replaced 5 minor fuses. Main fuse blown, which is a good thing.

Getting dead p/s, abs, locked shifter, brake light, blank Nav screen etc. The car doesn’t run very well or for long. 

The main fuse is a pita to replace. I realise now why some of the PAL main fuses you can buy have open ended spears rather than holes you have to screw into.

I was wondering if I could tear out the copper spades of the busted fuse so each spear would rip off each bolt. Then I could push in one of those open ended spear types. 

I guess a temporary fix rewiring the ends of the busted fuse is mad.

So depressing. Lexus dealer is quoting £375. It is a crap job to do so I get the price.
 

And of course there may be more problems with the DC inverter (replacement cost could spell scrapping the car) or the P/S fuse inside the HV Battery.

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Sorry to hear about your mistake 😞  When I was a teenager I had an Amiga 1200 with a hard disk at a time when hard disks weren't very common. It was only about 200mb or so, but the data I had on it was the result of many many hours of work tinkering and messing about. One day i did the same thing you did, accidentally connected its power cable the wrong way round and fried the controller board. Was absolutely gutted.

Hope you can get it sorted without paying too much. I'd be inclined to go for temporary fixes or maybe even paid diagnostics just to see the extent of the damage before spending too much.

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You will be very unlucky if damage to the hybrid inverter has occurred. The fuse within the HV Battery shouldn't have blow as that isn't directly related/connected to the 12v system.

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Good morning.

Isn't it easier to try at a car dismantling workshop?

Maybe you can find an RX400h and take the main fuse directly.

At least that's what I would do.

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I have ordered a 120 amp fuse. Getting one isn’t the problem. Fitting it, removing the old one are the real headaches. 

To test the system I will run a temporary fix. This will confirm that the ecu and modules are operational - that the blown 120 amp fuse did its job protecting the electronics. 
 

If it turns out I’ve cooked something I have only myself to blame. 

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1 hour ago, Greisingel said:

I have ordered a 120 amp fuse. Getting one isn’t the problem. Fitting it, removing the old one are the real headaches. 

To test the system I will run a temporary fix. This will confirm that the ecu and modules are operational - that the blown 120 amp fuse did its job protecting the electronics. 
 

If it turns out I’ve cooked something I have only myself to blame. 

Hope you manage to sort it Andy. Keep us informed!

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OK, so, I rammed in the 120 amp copper spades like a crown over the blown main fuse metalwork. It was a very tight fit and LED me to believe that contact was good. The bit I used to ram was from a new 120 amp fuse that had arrived by post. I made sure the blown part did not join (because the pressure of ramming brought the original blown fuse ends together). I assumed that you shouldn't have two 120 amp break point paths. It was ****** down with rain so haven't photographed.

1) I installed a new, tested full charge, 12V Battery.
No "READY" was given when I turned the key. P/S / ABS and Brake warnings appeared as before MAIN FUSE makeshift fix. Steering wheel wouldn't tilt / no NAV display / windows dead / Shifter locked in park
BUT engine fired up as normal and ran smoothly. There were clicks and thrums coming from the front.

2) I did the "Accessory" turn with the key, pumped the brakes twice and turned engine on. THEN I got the "READY" signal & steering wheel shift. Warning lights went off/ Nav display came to life (HV Battery showed 3/4s charged..looked normal). For a second I thought problem solved. It ran for 5 seconds then flipped back to 1) status.

I had hoped that I would prove that an operational Main Fuse (admittedly, a makeshift job with risks). That's where I am at the moment. I checked a couple of the mini blades I had replaced (that blew after the Battery short) could solve this. The fuses were fine.

I don't know what this means. Is it possible the MAIN FUSE makeshift fix is fouled up? I checked it and the crown is tight on the old metalwork. Sure it isn't satisfactory beyond testing

I guess I need to see some codes on techstream

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1 hour ago, Greisingel said:

I guess I need to see some codes on techstream

^^^^^^This

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42 minutes ago, Greisingel said:

Progress is one way of looking at it 😐

I forgot to mention that the Hybrid Battery warning came on in stage 2 (when all the other warnings disappeared).

Sorry I said what I did! 

Keep us posted. I am gutted for you.

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3A76777A-4CB6-4A1C-AE69-B10F5F5EA5D1.jpeg

Naughty temporary fix

So, my 113K miles RX appears to be working fine thank god. My temporary insulated crocodile clip fix holding in a 120 amp rated wire plus a non conductive block between the split fuse seems to work.

All electrics work except the steering wheel tilt at ignition. Will have to check that.

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No warnings yippee

Brand new auxiliary Battery behaving itself and maintaining 14.2 V charge.

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Consistent charging 

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I should add – this is a temporary fix. There would be a risk of fire and or major engine failure while driving.

I am sure everyone here is well aware that a blown/damaged fuse must be replaced by OEM or quality after market item.

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  • 2 weeks later...

Rigged techstream 13. Palaver. But worked. Got codes POAA6, C1259, C1310. Don’t care about the C ones. The P one a pain in the arse.

All this because I grounded live. What a tit. Maybe the hybrid ECU is now damaged.    

New 450A CCA auxiliary Battery fitted - the one I shorted. Seems to work fine. Maybe I should change it just in case it is defective. When the car runs it charges at a tidy 14 to 14.1 V fluctuation  

Also I am now convinced my RX400H has an indoor swimming pool judging by post heavy rains and window condensation. That’ll be another story. 

I sort of hope, though doubt, the problem is my rigged main fusible fuse. A 120 amp, non-OEM female fuse (see pic) rammed onto the old blown fuse ends I straightened. Auto electrician coming in next week to fit OEM fuse. 

When I remove the neg Battery lead and reset the car it then starts and runs, drives, accelerates and recharges normally. HV Battery maintains tidy 80% even with Red triangle Hybrid, VSC, Skid, brake warnings. Bizarre. C18C46F4-ADA2-4ED0-A019-776C1DBDA901.thumb.jpeg.cce5614e8e152187b36351b2b9aa0195.jpeg

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1 hour ago, Greisingel said:

Got codes POAA6, C1259, C1310.

New 450A CCA auxiliary battery fitted - the one I shorted. Seems to work fine. Maybe I should change it just in case it is defective. When the car runs it charges at a tidy 14 to 14.1 V fluctuation  

Also I am now convinced my RX400H has an indoor swimming pool judging by post heavy rains and window condensation.

First of all, the "450 CCA" rating of the Battery isn't important. All that tells you is that the Battery can squirt out 450A to crank the engine, but our cars don't have a starter motor to crank the engine with, and they take less than 20A to get the car into READY mode.

I'm busy with something else at the moment (just taking a Coke and biscuit break) so haven't got time to delve deeper, but it may just be possible that the POAA6 problem could be related to the water problem if that water is anywhere near the high voltage Battery - although this is just idle musing while I eat my KitKat.

If I remember correctly, POAA6 is something to do with keeping the high voltage isolated from the rest of the car so that you don't get fried. If that water has somehow made its way into the HV Battery pack or an HV connection somewhere, it could just provide a conduction path for high voltage leakage. If that were happening though, surely the hybrid system should shut down and not allow the car to reach READY mode?

I'll keep my thinking cap on while I finish off my job 😊

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Thanks for getting back. You’re right. I was looking for more Amp hours. But the high CCA may have shot a bigger short down although still 12V

Correct. The POAA6 is an HV isolation issue. And water is typically the problem in the Rx400h that clearly has a water ingress flaw.

Agree. If there was a Hybrid Battery short somewhere in the mix it would cease to work. I think, anyway. It would be a coincidence that water ingress was now the problem just after I’d reversed Battery pole  

Yes, the fact that everything works, charges etc is a puzzle. But it will only start after the aux battery reset. Even Techstream couldn’t reset it for a start. I haven’t driven it over 80mph, a speed often quoted as a sort of limit in hybrid issues while a vehicle operates. 

But these INF sub codes for a POAA6 thrown helps narrow the short or malfunction. 

I do wonder if my 120amp fuse bodge is causing problems. Will see when the OEM one goes in next week  

Cheers. 

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Update:  

I have discovered moisture under the carpets. Looks like I have the notorious Rx400h leak issue. I guess from the upper trunk seams around lid hinges.

I’ll be stripping her out. I have seen some unbelievable moisture compromises in this model. There is a Russian YouTube fix that has water sloshing about. 

First move your RX400H so nose points downhill as steep incline as possible. 

Then force a READY with neg Battery strap reset. 

Then run the car with blower on full heat to floor. (I live in wet Blighty). One thing I do like about Rx400h (and the liking is getting less by the day) is the heat cool cycle is less of a worry as I let her idle all day. 

Then buy a waterproof car cover. 

Then maybe get a dehumidifier. I am hoping I have at least identified the problem and can find a way out of the misery of my OCD and cars thing. Cheers to Margate over clublexus, who has been absolutely superb. What a good guy he is. 

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