73standard

I have a problem on my 2004 TL where the car thinks the rear driver side door is open when it's closed, but only when the engine is not running. The display will show that door open and when I go back there and push in the switch all the way by hand, no change. Then when I start the car it thinks that door is closed, as it should be indicated. When I go back and actuate the door sensor by hand the display toggles from door open to door closed properly. About 3 weeks ago the same exact thing was happening to my passenger side rear door and it just sort of went away. Earlier today I found my battery at dead zero and replaced it, however the door sensing problem described above still exists. I've verified that it's not the door sensor - it correctly grounds the wire when the door is open and lets it float when door is closed. Do you think it could be the MICU going crazy as my battery was getting low? Is there any way to reset the MICU so I could test it out? Thanks in advance for the help.

CurrentDraw

You can tackle this problem numerous ways, this happens to be my personal method. The first thing to do is remove the drivers front kick panel out of the way so the micu is exposed. Using a decent flashlight check for any water intrusion, corrosion, and/or water witness trails, also check under the floor mat for a damp/moist carpet. There are connectors at the back of the micu as well and you will have to check those thoroughly.

As you mentioned above 3 weeks ago the same thing was happening to your passenger rear side door and it went away. Water intrusion due to clogged sunroof drain tubes or an aftermarket windshield will find its way into or around the connectors/control units. Water, under the right conditions can become a good conductor and can short two or more paths together which may create an unintended result such as the one you are experiencing.

If all looks ok with no signs of water/corrosion then you can proceed further. Using a wiring diagram you will need to find the connector which houses the terminal for the drivers rear door switch at micu. After disconnecting the connector at micu, carefully check the male terminal pin coming out of the micu with a dvom/test light. If you measure a ground at the terminal pin then you have an internally shorted to ground path and the micu will need to be replaced.

Leave the connector at the micu disconnected because you will have to do a last test to make sure the wiring from the drivers rear door switch is not shorted to ground. Locate the female terminal pin at the harness side of the connector which receives the signal from the drivers rear door switch. With the door switch pushed in you should not have a ground signal, with the switch in its fully sprung open position you should be measuring a ground signal. Message me if you need any help with diagrams.

73standard

Hey CurrentDraw, thanks for the very detailed help! I did some checking yesterday before I posted and it was very difficult to find which connector had this green/yellow wire going to it. I think it's one of the 2 huge connectors with like 40 wires in each. When I unplugged the one nearest the door, everything seemed to go down (door sensors, dome light, display, etc.). Unplugging any of the others did not disconnect the door sensors from the MICU. Do you know where I can find a more detailed diagram that could point me to the exact connector and pin location on the MICU?

I also measured the voltage at each door sensor wire with the door sensor removed. There's quite a voltage drop from the battery to the door sensor wires, especially when the engine's not running. Here's what I measured:

Voltages while engine not running, display reporting LR door open (all sensors are disconnected)

• Battery: 13.1 V
• LR door sensor wire: 9.1 V
• RR door sensor wire: 11.3 V
• LF door sensor wire: 11.2 V
• RF door sensor wire: 11.4 V

Voltages while engine running, display reporting all doors closed (all sensors are disconnected)

• Battery: 15.5 V
• LR door sensor wire: 15.5 V
• RR door sensor wire: 14.2 V
• LF door sensor wire: 15.5 V
• RF door sensor wire: 15.3 V

I'm guessing the problem is related to whatever is dropping the voltage at the door sensor wire down to 9V when the engine is not running. If there's a diagram that can point me straight to which connector and pin I can do the tests you recommended much more quickly. Again, thanks for the help.

CurrentDraw

The connectors are located behind the relay box. E is a 16 pin connector and H is a 14 pin connector.

flyromeo3

I had the same problem/symptoms a few years back and it was caused by a leak that developed on my windshield by the A pillar.

73standard

flyromeo3, did you have to replace the MICU? Where did you see the evidence of water?

73standard

After I swapped the battery for a new one and drove it arsound for a while the voltages at the door sensors were normal and I haven't seen the problem since (7 months ago).

justnspace

iTrader: (1)

Awesome that you came back to update us!!!