While starting my 2006 MDX, The head lights try to come on, the hvac led flashes, the windows go up and down . . . but car starts and the aberration continues . . . please advise

 

Sounds like an issue with the passenger side Multiplex Integrated Control Unit (MICU).

 

Thanks! Why passenger side? Is this something I can replace as a capable "shade tree mechanic"?

 

It can be some other part of the multiplex integrated control system, since the driver's side under-dash multiplex control unit (MCU) does communicate with the passenger side MCU; but, the under-dash passenger side multiplex control unit (MCU) is:

• part of the circuit that provides power (+) through the power window relay
• supplies the ground signal (-) to the both headlight relay coils

The MDX suppose to have a self-diagnostic feature to blink the trouble codes via the ignition key light; however, I currently don't have the information for the self-diagnostic procedures and codes.

There is no guarantee that it is the passenger MCU without tests though.

The passenger MCU is separately replaceable from the under-dash fuse/relay box. The unit should just unplug from the various terminals on under-dash fuse/relay box.

 

Thanks Tech8 . . . One thing I forgot to mention is the buzzing under the driver's side . . . Does that make a difference in your diagnosis? Also, to be more specific, everything is fine through the "acc." key position, it begins at the "on" position through run and doesn't stop until back at off . . . I'll see if I can find the diagnostics . . .

 

I recall an earlier discussion of the buzzing under the driver side and it did have something to do with the corresponding multiplex unit.

 

If you're referring to a buzzing sound when you try to start the car, the buzzing sound is coming from the starter cut relay. It is usually caused by faulty ignition switch contacts. Replacement of the ignition switch (electrical portion) is relatively easy and not too expensive.

The buzzing noise is not usually due to a multiplex issue.

 

buzzing starts at on position before start

 

Turned out to be loose ground under dashboard driverside . . . Accessible through opening after removing upper side cover

 

Did fixing the loose ground also resolve all the other issues?

 

Yes . . . All of them

 

Great, that everything is resolved without need for replacement.

I kind of wonder if someone previously did something related to the ground bolt though; as, it normally wouldn't loosen if it never been removed.

 

My guess is it was never totally tightened and as the loosen wires at the connection have slowly deteriorated, becoming more resistant, the tightening became necessary to break through some minor oxidation and make better contact . . . While the screw appeared to be snug, the wires moved when I touched them . . . I was able to, with some force, turn the screw 1 and 1/2 to 2 full turns . . .