Drivers Door Control Problem - Help Please!

[johnatg]

No - I wasn't offered the old parts this time and I forget to ask in my shock at the new bill! Does make me wonder a bit though - it had occurred to me since - did they realise themselves that sort of thing might have been the problem all along and they didn't want me to know that's what they'd found?

[Ashpoint]

John is not too late for you to revisit the dealership and to ask them to give you the 2nd set of damaged components?

Several further questions:
Did they make you pay for the 2nd CPU unit? I would imagine that the 2nd one should have been covered under warranty that the 1st replacement carried.

We have some very "well-connected" folk reading and participating in this thread. I wonder if any of them would be moved to research if the components have in the past been subject to a recall by Toyota/Lexus?

[johnatg]

I suspect that they dumped the parts last Thursday when they fitted the new ones. I collected the car on Friday 'cos they said they wanted to test it some more. Hmmm.... I intend to write to the dealer principal about the 'warranty' on the part fitted the first time. It really isn't good enough, is it?

I fitted a 10a fuse in place of the 20a one protecting the door lock (in the fuse box under the dash driver's side - actually part of the junction box/ecu). Ran it through quite a few lock/unlock cycles - it didn't blow - no problems so far! I just knew that fuse was too damn big. Maybe I should try 7.5a! I'll give it a little while though.

I'd be interested to know if there are any Tech Service Bulletins about this, but I doubt it - Lexus Stockport claimed they had been on the dealer forums (where they no doubt complain about irritating customers just like we complain about them ! ) and they said no-one had come up with anything. And the guy who did the work said he had never replaced on of these JB/ecu units before.

[toffee_pie]

what is the recommended fuse for the door? putting incorrect fuses is not really wise.

i read a few lexus forums, i never came across this fail myself.

have you the po40 installed again?

[johnatg]

The standard fuse for the door locks is 20a. Can't do any harm fitting lower values - a lower value one may blow prematurely, but that's all. I'd never fit a higher value. The wiring in this car can certainly not sustain big currents. Most of it is very thin/lightweight indeed. But electric motors do cause a big momentary surge/spike on start up - that might be why they fit fuses way bigger than obviously needed.

Re PO-40 - no. My original one is on it's way to Michael and his techs, and he's sending me a replacement which hasn't arrived yet. I must say he has been most helpful - several private emails apart from public corespondence here.

[toffee_pie]

aye, he is a top bloke, I have a po40 and its working fine. I don't think there is anything wrong with that.

[Ashpoint]

John, I would be inclined to NOT cycle the Lock/Unlock function in a way which would be pushing past the normal. In other words, the normal operation would be Unlock, jump in the car, drive away. Upon return, Lock and walk away from the car. A single motion every several minutes.

Having said that, I've often demonstrated the Po-40 Folding Mirror Kit at functions where 4-6 rapid, full cycles was often the norm.

The new Po-40 (tracking number:LK907979238AU) is shown as having passed through Sydney Export on Saturday. It should be with you by Friday (probably Wednesday)

Even then, I would not rush to install the Po-40 until you have confidence that the car is reliably normal. Also, please use the T-quick harness, which is designed for your model and only requires 3 splices to existing wires.

I also meant to comment previously, to congratulate you on finding the @#$%$# fuse box (there's actually 2 of them inside the car) hidden as they are above your legs. Did you also discover the iddy-biddy "fuse extractor tool"?

As to other unsolicited comments - <blush>

[johnatg]

Doh! No wonder the fuse didn't blow! Wrong one - I replaced the power window/mirror fold fuse. But I've just tested those - even running both window and mirrors together - no problem.

The door locks are protected by a 15a fuse - I'll change that for a lower value tomorrow.

Michael - points taken. And no - I can't find the fuse extractor, though I know there's supposed to be one. Been using pliers - actually those fuses need a hell of a pull to get out!

[Ashpoint]

It is <ahem> hidden in the fuse box located in the engine compartment. Then again it is a liberty to call it a "tool"

[normski2]

The fuse puller is often in the main compartment, under the bonnet, but sometimes it may have been stashed in the forward fuse box rhs of engine towards the front. They really do make fuse extraction very simple.

[Mouser]

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.

This is my view as well. The components are clearly destroyed by overcurrent. The causes of overcurrent are either a short to ground in a wire or a fault to ground in the component being driven. That the door fails to unlock properly suggests this is a prime area to look.

The scientific approach would be to measure the current draw of each connected device on the passenger and driver's side and identify where one side is anomalous. You may find something peaking at 100A+, even with a 10A fuse. Fuses blow quite slowly, wherease ICs / diodes and other components can suffer serious damage in a very short amount of time. If you're not comfortable testing current draw, resistance testing can be indicative, but should really be confirmed prior to announcing a diagnosis. My suspicion is that a wire has worn through, or a connection has shorted out. Given connections and wires can comfortably handly such current for 1/10 of a second, you may see no burn damage.

[Ashpoint]

Firstly, can I thank John for creating this thread and particularly also to the very considered specialised knowledge laden responders. It has been a wonderful educational adventure..

For readers of this thread who might never have seen a Po-40 Folding Mirror Kit in the flesh, it might be useful if I give a tour of the physical Po-40. See the photo attached.

The area of blackness seen on the right of the wiring harness is a built-in fuse. The fuse should be either/or/and protecting the car/control module.

South of that "landmark" you can see a few of the shrink tubes that you are encouraged to use to cover the 3 wires that need to be spliced.

BTW the harness shown in the photo is what we call the Universal Harness which enables the Po-40 to connect to different styles of cars. John should have used the T-quick harness that I sent him where he would have only had 3 wires to splice and two ready-made plugs and sockets to be swapped.

All the rest of the "smart stuff" is in the 6cm x 6cm x 2.5cm component box and embedded in epoxy. There's not a lot of chance that we could have even an occasional short to +12 V or to ground in that environment.

That's history now and the only difference in the end between the T-quick and the universal harnesses would have been the additional work he had to do. The overall result should have been (and was for 6 months) a working folding Mirror system. .

[Ashpoint]

Readers of this thread may be interested to know the results of testing to date on the control module and harness that John retrieved from his car and submitted to the manufacturers in Bangkok.

We anticipate a further report when the engineer investigates the performance of the units in freezing conditions.

I test the unit and harness that you send back to Thailand

<< visual inspection >>
from outside the box
no melt , burn , rust , liquid leak or any sign of problem
for both control unit and harness

<< input impedance @ room temp (24-32 C) >>
blue vs black wire --> OK
white vs black wire --> OK
blue vs white wire --> OK

<< input current @ room temp (24-32 C) >>
blue wire --> ok
white wire --> ok
red wire --> ok
orange wire --> ok
pink wire --> ok
purple wire --> ok

<< manual testing @ room temp (24-32 C) >>
lock input --> ok
unlock input --> ok
fold input --> ok
unfold input --> ok

<< auto testing @ room temp (24-32 C) >>
10 cycle / 60s --> ok
30 cycle / 180s --> ok
10 cycle / 600s --> ok
50 cycle / 600s --> ok
5 cycle / 1800s --> ok
10 cycle/ 1800s --> ok

no short circuit report
no over current (2000mA) report

after this testing i will test for longer period and try to find the way to test @ temp near freezing point
(may be i will put the control unit on the ice and test it)

[ColinBarber]

[BillNick]

I was just reading this old thread searching for some clues about my own issue.

I wonder if the electrical experts following this thread could offer me some help to diagnose my problem:

My car locks and unlocks as expected without fault using the key fob.

As soon as I place my hand inside the drivers door handle, the car unlocks itself repeatedly over and over until the door is opened.

I get in and shut the driver door and all is ok.

If I start the car with the door open, upon closing the door, the car unlocks itself twice, flashing the indicators and flicking the locks each time. This also happens if I press the door close sensor rather than actually closing the door.

So it seems I have a bad earth or a short or both related to the open/close sensor on the drivers door - would you agree?

I have a PO40 fitted which has been working trouble free for almost 2 years now.

Where should I look first?

[ColinBarber]

I'd look for water ingress within the door, fuse boxes and junction boxes. Also the door actuators have a sensor in them which tells the ECU if lock/unlock has occurs. If the actuator becomes faulty and the ECU doesn't detect an unlock then it can try it multiple times.

[BillNick]

Ok so I will get the door card off and do a thorough visual inspection in the footwell also.