Electrics malfunction - Please Help

[john2k]

My 2008 IS250 with 70K miles has developed a really odd electrical fault. It was perfectly fine one minute then next everything started acting up. When I toggle the headlight stalk on and off, the relay doesn't always kick in and i have to repeateadly toggle the stalk then eventuall it turns on. When it turns on, the cluster doesn't register it as on. The door locks dont always work. I have to keep locking and unlocking. The telescopic steering tilt is also intermittent. The high beams are intermittent too. The dome light doesnt come on either. Sometimes when I fiddle with the door pressure switch by pressing it back and forth then it triggers something to work. 

I checked all the fuses LH and RH in the interior. I also checked the ones in the engine bay. I checked the ground points that are visually visible at the top of the engine bay and all are good. I purchased techstream to try and see any error codes. I can connect to the body ECU and there are no faults stored there. However, I cannot seem to connect to the combination meter or the gateway.

I'm hoping it's just a ground connection issue somewhere. But i've checked the ones on the top on the engine bay. Is there any particualr ones I should be checking? Has anyone had this sort of problem? would really appreciate some help. I thought these Japanese cars are supposed to be bulletproof when it comes to electrics. Right now this is behaving like a french car with electrics from the nineties 

[Mr Vlad]

Hi John and welcome to the best Lexus forum there is. Unfortunately you've an issue with your car which is not common. 

You've done the correct thing by getting techstream. Have you done the Health Check test? This tests every ecu in the car and reports DCT codes. It takes a while to do the test. 

As for connecting to the combination meter and gateway. I'm not sure you can on the copy version of techstream. 

One thing you could do before anything else is disconnect the Battery and leave it 45 minutes. Reconnect and see how you go. You'll have to reprogram the windows and sunroof and possibly the radio so make sure you have its code.

I take it you don't have any lights on the dash such as warning lights. 

[Spock66]

I'd suggest getting the Battery and alternator checked as a first step.

[john2k]

53 minutes ago, Mr Vlad said:

Hi John and welcome to the best Lexus forum there is. Unfortunately you've an issue with your car which is not common. 

You've done the correct thing by getting techstream. Have you done the Health Check test? This tests every ecu in the car and reports DCT codes. It takes a while to do the test. 

As for connecting to the combination meter and gateway. I'm not sure you can on the copy version of techstream. 

One thing you could do before anything else is disconnect the battery and leave it 45 minutes. Reconnect and see how you go. You'll have to reprogram the windows and sunroof and possibly the radio so make sure you have its code.

I take it you don't have any lights on the dash such as warning lights. 

Thanks for your reply. I did disconnect the Battery and wait and that did not help. The techstream does connect to the combination meter on my friends IS250. So definately communucation issue with those ECU's. There are no warnings on the dash and as mentioned when i turn lights on, it doesnt even show on the cluster.

13 minutes ago, Spock66 said:

I'd suggest getting the battery and alternator checked as a first step.

Battery is brand new and the alternator is good. Not to mention the problem happens even with car being turned off so the alternator is not in play. So car turned off, I unlock it and sometimes it doesnt and eventually it does, then i toggle the stalk and the lights sometimes turn on and sometimes dont. I have to keep toggling it. When it does turn on, it doesn't show on the dash. Sometimes it shows on the dash for a split second and disappears.

[Mr Vlad]

Like I said John. The copy version of techstream doesn't connect to combination meter or gateway that's why I suggested clicking on the Health Check scan.

It may well be an idea to source replacement stalks ot take yours off and inspect them as something may have come adrift in the stalk mechanism. It certainly sounds like a mechanical issue rather than an electrical one.

Example. What does one do when a light goes out in a room? Bulb checks out OK. You know the power source is OK and the wiring is OK so what's left? The switch. It can work sporadically and not at all.

Our is250's are absolutely superb cars but sometimes a bugging electrical fault happens. I've had a couple which are well documented here in this forum. 

Source replacement stalks, you may aswell get both sides.  

You perhaps could swap stalks with your friend just to confirm one way or the other it's the stalks. 

[Herbie]

There's a few circuits involved here so you need to get a wiring diagram and see if/where these circuits have common points.

It'll probably be a loose/dirty connection on the earth (ground) side somewhere, but you'll need the wiring diagrams to find the locations of the joints.

If you look here https://www.lexus-tech.eu/Menu/Repair you can legitimately buy a block of time (something like €5/day, €10/week) to access the wiring diagrams and you can also print as many pages as you want/need while you have access.

[Beamish]

 

Have you double checked the main ground to the body from the Battery? 

It is awkward to access so it might be an idea to run an additional earth cable from the Battery negative to a good body earth to see if this resolves anything.

Dec.

[Mihanicos]

Using a wiring diagram, connect the negative terminal of a multimeter to the Battery negative terminal and disconnect it from the Battery. With the positive probe of the multimeter check the wiring of the car towards the suspected circuits causing the faults. Check each connector as well by disconnecting them one by one and measure the circuit resistance to that point. Ground body points connected to wiring grounds should be checked as well.

You should never get a reading of more than 1 ohm. Alldata are the best wiring diagrams, accurately redrawn so they are crystal clear and staight forward to read and follow.

They give you the precise location of each connector with photos.

The Lexus/Toyota wiring diagrams are good but not so easy to read and follow, they are the next best. 

If you find nothing wrong you need to check the communication circuits. You may have a module that has an intermittent fault to ground or shorting the communication signal.

Check first the resistance between the communication channels from the 16 pin obd2. Measure accross the right pins, I need to look up which is which. If my memory serves me right you should get a reading of 120 Ohms. Other members with better memory, please correct me. If you get a reading below, you need to disconnect the modules one by one until you get the desired reading. A better way to check the communication channels is an oscilloscope or a picoscope. There you can see the waveform of the communication signal. 

Intermittent faults take time to find and a lot of patience. With time, one day the intermittent fault will become permanent and then it is easy to locate.

Chris.

 

[Linas.P]

Lexus are great cars until they get electrical problems... been trough that myself... this should not be confused with problems like French/Italian cars have - those just randomly fail from wear and tear. If Lexus has electrical problem then there are only few reasons for it - water, somebody shorted something out in the fast and fried something, of somebody fixed something and screw it up. By themselves Lexus do not fail, but if for example you get water in the system then it isn't really cars fault.  

A lot of good advise above, but I tend to think some of it goes way too deep... First of all - do you have any lights on the dash? From problem description it sounds to me like not, so there is no point reading codes, checking comms between the modules with oscillators etc. It is not bad advise, but there is nothing indicating you need to do that yet. So far it sounds like straightforward electrical fault, either open or short circuit somewhere, maybe multiple places. So for time being I would put Techstream to the side and would systematically go trough all the connectors to check if are maybe corroded. If it is broken wire, then it will be major pain in the backside as there is not easy way to find it. So far your issues seems to affect random things around the car, so let's hope it is just maybe one major junction that is corroded and shorting many things out.

Because you said your engine is running fine I would not be looking at any issues there... I advise to look to main grounds in the interior of the car, as well main junctions under the dash... in my case the big junction plug on the passenger side was randomly corroded, have no idea why, because that was the only connector that was corroded and nothing else around it. I was speculating maybe sunroof drain, but again why would only one connector corrode and not the others?!

Anyway - marked out areas where I would start looking... let me know if you need diagrams. 

 

  

[john2k]

Thank you all for all the suggestions. I've been busy past few days with this trying to figure out what is happening. I've checked the main ground point from the Battery to the chassis and it's solid with no corrosion. The ground point under the airbox was a bit rusty so i cleaned that but it made no difference.

@Linas.Pthanks for that illustration. I checked all 4 of those interior ground points (2 by the centre console and 1 on passenger side and one on driver side) I also unplugged every connector in the junction boxes and inspected the pins for any corrosion. Everything is solid with no corrosion whatsoever.

Now I am back to the drawing board as to what is going on. The engine runs good and I able to drive. It seems anything to do with body control electronics is all playing up. Sometimes the lights, sometimes the telescopic tilt steering, sometimes the hazards, some times the windows and locks. If I open and close the door sometimes I can hear as if the car is trying to unlock the lock even though it's already unlocked. When I turned the lights on, this does not show on the cluster. But when I open the door it shows. But some times it will show the door is open even though i've closed it.

I've got access to the repair manual witht he diagrams but now hit a brick wall as to what else to try.

 

[Linas.P]

Lacking any particular codes hard to say... MPX system controls quite a few things that you mentioned are not working, other parts related to them may be Power Source or Main Body LH/RH ECUs. Gateway ECU as well could be related as it interconnects MPX, BEAN and CAN-BUS. But this is needle in the haystack situation. 

[john2k]

26 minutes ago, Linas.P said:

Lacking any particular codes hard to say... MPX system controls quite a few things that you mentioned are not working, other parts related to them may be Power Source or Main Body LH/RH ECUs. Gateway ECU as well could be related as it interconnects MPX, BEAN and CAN-BUS. But this is needle in the haystack situation. 

I'm also thinking MPX or gateway ecu. Where is the MPX system? does it have an ECU? The sort stuff that's malfunctioning is mirror adusters, lock/unlock, indicators and hazard, lights, dome light not working at all (only reading LED's work), start button backlight, boot not opening. And usually when wipers are turned on if i turn car off the wipers have always just stoppped where they are when i turn off the car. Now they dont stop.

[Linas.P]

I meant to say BEAN/CAN-BUS/AVC-LAN

MPX=BEAN:

[steve2006]

You mention the door locks are intermittent and from past experience the door lock actuators or more specifically the motor inside them are known to fail as the brushes wear out.

On my previous LS400 the offside rear door one failed and at 20MPH the automatic door lock system kicked in but continually cycled due to the failed actuator.

If the actuator stops between locked and unlock  this could result in a totally confused ECU which in turn could result in further problems just from the fact the ECU is now in limbo.

Jump in the car and try locking and unlocking the doors several times with the key fob and see if one of them fails to lock/unlock.

I may be miles away here but thought it worth mentioning.