Drivers Door Control Problem - Help Please!

[toffee_pie]

any update on this?!

good i hope.......!

[johnatg]

Well, they've fitted a new door loom and a new junction box and they claim that everything works OK. But they haven't found anything else. They are keeping the car at least until tomorrow (Friday 30th) to do some more tests. I'm nervous about taking it away - it's going to get a good dose of door locking, window winding and miror folding before I do take it.

I'll let you know how that all goes!

[toffee_pie]

yeah, i imagine if it goes wrong that car will have to go? cant see you wanting to put more time and money into it, hopefully that new loom and x box will do.

[Ashpoint]

If I recall correctly the first CPU module which was replaced, worked perfectly for several days before is also crashed. I wonder if there is a explanation for that situation. It seems to me that just replacing the CPU module did not fix the problem that existed/exists outside that module.

Do you know if the second module burnt up in the same fashion as the first?

I'm confident that Lexus will warrant the parts that they have replaced, so if those parts crash again, it won't be to your expense – but I would want confirmation of that.

I would hold off reinstalling the T-quick harness and the Po-40 pending a report from Bangkok as to any issues with your Po-40 control module. Even then, I would be as nervous as you. I think I mentioned (maybe in a pm) that I have sold my Lexus and now drive a BMW without folding mirrors – I really do miss them. Already the lady in the adjacent car spot has bent my mirror out of shape <sigh>

I see that one of the contributors has suggested that the car maybe should go – I'm 55/44 inclined the same way.

Just a lot of testing ahead for you, John. I think this thread has created a lot of interest and it will be interesting to see when everything settles (and why)

.

[johnatg]

Just one correction there - it was a couple of days before the second Junction Box burned out, but I hadn't gone anywhere - just drove home from Lexus - about 10 miles, and parked up. Next time I opened the car, after a couple of minutes idling whilst I cleared ice from the windows, the 'RH Door' sign was on all the time again - it had gone again.

I just hope I can love the car again!

[Ashpoint]

That makes me concerned about the Po-40, the connections, the weather.

I wonder if Lexus had cycled the Lock/UnLock functions after they replaced the CPU module? Surely the Po=40 was working then.

[johnatg]

Yes it was. And I checked that the lock/unlock and mirror fold worked before I drove the car away. Whilst it was parked up I did unlock it once and then single locked it, and it was the next time I unlocked it that it failed after a few seconds.

[johnatg]

Well, I've got it back - so far so good........

Another gut-wrenching £1138 though... :(

[Ashpoint]

How is this for a scenario...

• (Po-40 installed in the car – has been working 6+ months reliably)
  
• Car parked outside overnight, mirrors folded, extremely low temperatures and mirrors frost locked.
  
• Car unlocked using key fob / door handle / Po-40?
  
• Small pieces of road grit combined with frozen water trapped in the mirror sliding faces.
  
• Car attempts to unfold the mirror against frosty resistance.
  
• CPU module overheats and commences the burn damage.
  
• Car warms up and driver manually tests fold/unfold whilst noticing slow deterioration of functions.
  
• CPU module replaced (warm conditions) and all functions normal.
  
• Car parked overnight outside.
  
• Next day strain again with the circuitry as mirrors unfold against gritty resistance.
  
• Second CPU module burns up.and is replaced. Po-40 removed and is enroute for factory (Thailand) report. Door loom replaced.

Can the mirror sliding faces be inspected and/or lubricated? Look for abnormal wear, score or binding marks?

[johnatg]

The mirrors fold/unfold smoothly, quietly and at normal speed with the internal button. And with the PO-40 for the brief period between burn-outs of the junction box.

I am considering replacing the fuses protecting the door locking, window winding and mirror folding with smaller value ones - all are at present 10 or 20 amps. I have a good supply of 5, 10, 15 amp fuses.and could easily get more.

What do you think, and which ones would be useful to replace? Even if they blow, at least we might find the minimums which will work in service and provide some protection?

[toffee_pie]

I think that car has reached an untimely death, or is very close to.

I would be weary of spending anymore money on it, its 9 years old., can you write that off with insurance?

[johnatg]

Thing is, apart from this one electrical problem, which hopefully is now cured, it's perfect - and only done 46K miles. Absolutely no reason it shouldn't be good for another 100K! And it's had no problems otherwise since I bought it 3 years ago. Not me to give up on a car!

But I must admit - IS250 electrical systems are more than I can cope with - but also more than Lexus dealers can cope with too, I suspect!

I usually keep my cars for a long time and a lot of miles - my records are 17 years with a Pug 205 (that was my wife's, but I kept it going), 15 years with a Fiat 128 (originally mine, but passed on to my wife), 115K miles with a 1960 Sunbeam Rapier, 90K miles with a '88 Mazda 626, 90K miles with a MX-5 (not my present one - that's 23 years old but I've had it for 9 years) - those are in my ownership, not totals - and several others for a long time and lots of distance! You get the picture!

[toffee_pie]

this problem is fixed? if the milage is that low, its surprising. :)

I would be gutted to scrap a car like that with such low miles.

[ColinBarber]

do you still have any of the failed junction block assemblies?

[ChumpusRex]

Would be very interested to see more detail of the failed junction box assemblies.

In my experience, most of the modern ECUs like this are heavily protected internally. I've only ever seen two or 3 catastrophic failures like this, and they have always been short circuits in the loom.

I can't match the photo of the failed PCB up with the outside of the ECU, so I assume it is some sort of internal intermediate control, though given the fault description, it does sound like the problem was the locking circuit. The switch issue could be a reflection of the fact that the body ECU sends the door switch signal to the dash, and that the ECU was malfunctioning at that time.

The locking motors are reversible - the ECU connects them one way round to lock, and the other way to unlock, and disconnects when idle. A short to ground or 12V on one of the lock control wires could certainly cause this type of burn out. Ashpoint has posted an extract of the wiring diagram with these wires highlighted. I'd check these wires very carefully, as they are my prime suspect. Being unable to lock the door, suggests that the lock motor might have been jammed on in unlock mode.

The other thing is that the body ECU doesn't do very much high power stuff, except for the door locks and the windscreen wipers. Most of what it does is sensors, controls and interior lighting.

I don't know what a P0-40 is, but I guess it is something to do with the mirrors. The mirror retract circuits are nothing to do with the body control ECU. So I doubt it's that.

[johnatg]

It's not the body control ecu, which is located on the nearside (left) of the dash. It's the junction box, which is located on the right hand side just behind the dash panel. It's certainly the most complex junction box I've ever seen, but it's circuit board consists almost entirely of resistors and capacitors with a few diodes etc - there are (apparently) no logic elements there. See a photo, links to which were posted back in this topic somewhere. I haven't got (or seen) the second one, but am told it (the burn) was very similar.

I agree entirely with Mark's diagnosis, had reached exactly the same conclusions and tried to emphasise the things he said there when I took the car in to Lexus last week. As I said, I don't think they were too impressed - garages never are when you try and tell them what's wrong!

I guess Lexus tech also came to that conclusion, which is why they told L Stockport to change the loom. But I'm not at all convinced that they checked the lock properly, except in so far as to say 'well, it works now'. Which it does....

[toffee_pie]

I told you, wasting time going to lexus, all they will do is swap out parts, (at your expense) and hope it works, they wont debug or find the root cause, they have bigger fish to fry than dealing with your car, truth be told.

This does look like a short circuit for sure, is your key ok? i mean when you lock and unlock are you sure thats all it does? maybe the whole signals are gone haywire. Can you get a multimeter can check for continuity/shorts across the points mentioned previously on Mikes schematic, Its not easy to do but this its the predicament you are in, either get someone else to do it or do yourself.

I would definitely stop taking this car to lexus, look for some local garage and explain the fault, usually they can barter a decent price.

[ChumpusRex]

It's not the body control ecu, which is located on the nearside (left) of the dash. It's the junction box, which is located on the right hand side just behind the dash panel. It's certainly the most complex junction box I've ever seen, but it's circuit board consists almost entirely of resistors and capacitors with a few diodes etc - there are (apparently) no logic elements there.

There is a body control ECU on each side of the dash. The photo you posted is the main (right side) body ECU. Lexus call it variously either "body ECU right side" or "cowl side Junction box Right", mainly because it is basically 2 parts fused together.

The ECU needs more connections than it can fit, so it is built into a junction box. The ECU is the white middle layer in the photos. The junction box is the bottom layer, and the gateway ECU is the small one stuck onto the top.

The main burn appears to be on the bit of the ECU PCB where the drivers door open switch connects in, which probably explains why this was one of the first symptoms, but there is nothing high power that connects there. I suspect the big diodes (and some big components on the other side of the board) do some heavy duty switching, and that is what overheated.

[johnatg]

Mark's post has prompted me to do some more dismantling of the original Junction box/ecu (!) and indeed under the circuit board I showed originally there are some bigger components, including two ics with approx 130 pins each along with some big capacitors. There isn't really any damage evident on that side of the board except to the connection links to plug P1 (see page 14 of the Door Lock control circuit pdf which Michael provided on page 3 of this topic). The wire links are badly burned, especially pin 1 but also pins 5 -10 and 12 and maybe one or two more on the bottom row - does that provide any clues?

I thought the door lock was mainly controlled from pins 1-4.

I've also realised that the fuse box under the dash, driver's side is actually part of this Junction Box/ecu - at least that's a handy source of some more fuses! The rh door lock fuse is 20a - does it really need to be that big? Even at 5v that means it can pump in 100W. Any idea how much peak power the door lock really needs?

Thanks!

[toffee_pie]

re program the central locking? i would start from basics, something is causing that control box to blow up, its connected to the drivers door it seems, you already replaced the loom and the box so its not either of them.

what else is there, even if you want to get this fixed you need another control box, not knowing if you can fix it or not, can you get one from a breakers yard? i would take off the loom from the passengers side too and see if that has any effect.

[Ashpoint]

Eric's (toffee_pie) suggestion that a CPU box be sourced from a breaker's yard is too late but worthy of mention if not but to expand our thinking when we have to fix our cars.

[toffee_pie]

John, have you physically disconnected both mirrors, with a control box in place? i would say not, but it would be a way to isolate the mirrors.

[johnatg]

At the moment I have no problems. I'm just trying to establish what might have caused the problem before to try and forestall it happening again. Maybe there was in fact a problem with the loom.

I feel as if I'm in a bit of a race to identify the basic cause versus running the car as it is - is it now A-OK or not?!

[toffee_pie]

hope its fixed for good.......!

[normski2]

At the moment I have no problems. I'm just trying to establish what might have caused the problem before to try and forestall it happening again. Maybe there was in fact a problem with the loom.

I feel as if I'm in a bit of a race to identify the basic cause versus running the car as it is - is it now A-OK or not?!

John did they allow you/did you ask to have the old door loom. It would be good to inspect it thoroughly.

Has it been chafing against some other part in the door?