Hi All,

I've been an owner of a RX400H for a couple of years. It seems to be having a breakdown issue around once a year which is a bit of an inconvenience but probably need to fix. Having looked through the service history it looks like the previous owner was also facing it. I am trying to work out whether I should go ahead and send the ECU for repair or whether it could be something else? Here are the diagnostic reports:

Lexus:
HYBRID WARNING LIGHT PLS INVESTIGATE-
CARRIED PUT DIAGNOSTIC TEST, SEVERAL FAULT CODES STORED. CLEARED CODES, ONE REMAINED, LOCATED TO SKID CONTROL ECU MALFUNTION, SUSPECT 'MORE THAN BLACK BOX CAUSE WHEN REMOVED WARNING LIGHTS WENT OUT. POSSIBLE CORRUPTION OF ECU

Then AA report from earlier this year:
Patrol found the following fault code/s:System : Anti-lock braking system ABS - 49M / Driving safety system ESP Electronic stability program ESP 9.6.2 Status :C1241 - Supply voltage. Error Message : Faulty. Error static.Won't go in to gear, Carried out diagnostic no related faults Carried out battery reset and normal operation returned advised requires further inspection at garage -

So when it happens, hybrid warning message comes up, I continue driving but wont restart once engine is turned off. Each time once the battery is reset it works fine. I replaced the battery with official toyota one and that hasnt solved it.

Any advice greatly appreciated!

 

What do you mean by battery reset? Simply turning the car off then on again? Even though you have a fresh battery I would still suspect it being the problem that code is quite specific. The brake booster module sometimes goes out on this model but you would have codes for that.

 

Your ECU has the electrolytic capacitors in it. So they can start to leak after 20 years and start causing phantom problems. If your having problems that are difficult to repair and they don’t make any sense, then you really should pull the ECU and inspect it yourself or have someone who knows what they are doing inspect it for u. If there are signs the capacitors are leaking then you should definitely get it serviced. It can cost up to $500 and leave the vehicle inop for a couple weeks. Or if you are good with soldering electric control boards, you could take care of it yourself. Eventually they will need to be serviced, so if you have the means, you might just start making a plan to get it done.

 

No it wont turn back on and the warning lights continue but when road recovery arrive, boosting the battery with a jump start seems to solve the problem. Perhaps I should try and test the battery then?

 

"Your ECU has the electrolytic capacitors in it. So they can start to leak after 20 years and start causing phantom problems. If your having problems that are difficult to repair and they don’t make any sense, then you really should pull the ECU and inspect it yourself or have someone who knows what they are doing inspect it for u. If there are signs the capacitors are leaking then you should definitely get it serviced. It can cost up to $500 and leave the vehicle inop for a couple weeks. Or if you are good with soldering electric control boards, you could take care of it yourself. Eventually they will need to be serviced, so if you have the means, you might just start making a plan to get it done."

That's useful to know, thanks. I'll start planning to get it repaired. Would this be advisable over buying a second hand one? I have noticed some pretty inexpensive ones online that I guess could be tested?

 

if it’s a second hand ECU then it could have the same issue. You could go that route, but you should still get it serviced. The issue with a second hand ECU is the immobilizer, you’ll have to swap the door locks and ignition key etc.
it’s not an extremely difficult job to take care off. The ECU should be removable in 10 minutes, if you can find someone in your area who specializes in electrical repair work, they would be able to open it up, identify the capacitors that need to be replaced, then get them ordered. You can reinstall the ECU til they arrive, and then take it back out and drop it off so they can replace them. You need someone with great vision and a steady hand so they can soldier the pinpoint connections. They should be able to very all the new capacitors have been reinstalled correctly so you can put it back in the vehicle and not worry about it for another 20 years

 

Does the hybrid use the same 12 volt battery as the non-hybrid?

I'd look into this first. 🤓
Looks like a clue here.

Hopefully not the ecm and may be too early to go in that direction without more testing

Intermittent problems are the most difficult to diagnose so I'd pay attention and take notes if it only happens once a year and hopefully you will see a pattern.

 

The Hybrid model uses a much smaller 12V battery than the V6 model.