cmasten

Now that I have the audio upgraded in my LS, we have uncovered a slight issue with the drivers rear door. The installers will work with me, but I thought there is so much knowledge up here, why not ask.

Everything else on the vehicle works perfect, its just this one door as if all the power is off or disconnected.(ACC or ON power it functions fine) I have checked the fuses under the driver side and the ones in the trunk, they are all fine and we took the front driver door apart to make sure any connections were good. everything seems secure, we even looked over the ECU in the door to make sure it didnt seem fried or anything, all functions on front and passenger doors are perfect.

Here are the symptoms: passenger rear door light wont come on with the door open unless the ACC is on. the other 3 turn on, with or without ACC.

The door lock actuator from the outside on this door wont lock the doors or with the sensing when you approach with the fob and grab the handle (as in the lights there wont light up).

The door closer that finishes off the door being slightly open wont grab and pull it in.

The trunk lights wont come on and there is no fuse or connection issue we can see. Its puzzling.

Any thoughts or ideas from this group, there may be something very simple ( I was hoping fuse or obvious connection) that were overlooking. I have the service manuals and will go through the troubleshooting sections, but appreciate any input to this puzzle

Thanks

CMasten

jstjohnz

Check this fuse:

RR-MPX-B2, 5 amp, in the trunk junction box, even if it looks ok, test it with an ohm meter

cmasten

thank you very much

CMasten

WhitBaby

If you strike out on that one, check it by replacing it with a new fuse. Some weakened (metal fatigue) fuse elements will show good on an ohm meter but will open up under load. An ohm meter only runs a couple milliamps through them looking for any degree of continuity, not like true loading with serious current flow.

I've seen that happen with brake lamps too...looks good on ohm meter but won't light up. New lamp worked fine.

Whit

cmasten

I appreciate the input, I am guessing its at the fuse level, all the connections check out and the door does unlock from the master switch and the light comes on with ACC, I would think that a disconnected cable would not do anything, but either the driver side panel or the rear panel as suggested is where the issue is. Ill just grab some new fuses and see if swapping them out does the trick, they are certainly inexpensive enough.

jstjohnz

The fact that your trunk courtesy light doesn't work seems to point directly to that fuse, a problem outside of the trunk JB wouldn't affect the trunk light unless it's a short that's blowing the fuse.

cmasten

the trunk light is actually this fuse according to the manual,RR ECU-B it supports: Seat belt buckle lights, trunk light. I have looked at that one also, but it is interesting that the locks are part of 15 RR MPX-B 2 as it supports:
Power door lock system, rear seat adjustment, interior lights, power trunk opener and closer, alarm.

There are two fuses under the driver side that speak to the power locks and lights on the driver Rear door, I looked at those and put an ohm meter on them, but point taken that maybe that is not enough. I have ordered some of the micro fuses for this vehicle and will replace them one by one, I can see perhaps 4 in total that may (I hope) have a positive effect.

jstjohnz

There are 3 wires that power the left rear door ecu, 2 from BAT directly and one from IGN. The fact that everything works with the key on tells you that the IGN wire is getting power, and the BAT wire from the driver's junction box is getting power, that's the one that supplies the power to operate the motors, etc. That MPX fuse in the trunk supplies BAT power at all times to the door ECU to power just those parts that have to be powered up constantly, so your problem has to be related to the +12V from MPX B2 not making it to the door ECU.

I can go to the manuals and give you pin #s on the connectors if that would help, but I would bet anything that your issue is directly related to that MPX-B2 12 volt power.

That unit in the trunk is a combination fuse box and ECU. IIRC that MPX-B2 fuse also powers some of the internal circuitry in the trunk ECU.

cmasten

i am humbled again, the expertise here is always welcome.

Thank you, this makes total sense now, I will have a chance to check it over the weekend, as I have to remove the sub set up and await for the fuses i ordered.

CMasten

cmasten

JSTJOHNZ.. I dont know how you know this , but i am grateful for your help. I had some of standard fuses, but not the micro.. but thought I would pull the sub anyways to see if the fuse was blown.. and sure enough it was.. and I dropped the standard fuse in and its all back on and working.

Thank you very much !

CMasten

jstjohnz

Your welcome, glad to hear you got it going.

Shibumi1

this thread is one of the major reason i love CL... on a road trip to miami this weekend my passengers in the rear noticed the power out in the seat..(had noticed pass rear door issue but put it on hold assuming the motor had simply gone out) checked all front fuse panels...completely forgotten the rear corner... voila' the 5amp fuse saved me a trip to service an in my mind $900 for a new door lock motor..( as tomorrow is my BDAY...) its now an even better 1 thanks soooo much!!!

Mikey100

So ...... Let's do it early ! ............

Happy Birthday, Shibumi !!!!!!! - - - - - - -

From your Club Lexus'ers !!!!!!

Best Wishes for Many More from ..... Mikey Lulejian on Lake Oconee, GA

Nospinzone

I wonder how old he is?

CJITTY

This is why forums are so valuable!! Excellent responses for a positive outcome! #awesome