'05 Avalon power mirror memory problem

[jeffcarp]

Anyone else having a problem with erractic behavior of the driver's side mirror, when using it with the memory seat presets? I have a mirror position assigned to memory seat A and a different position assigned to memory seat B. I've reset both positions to make sure they were still assigned.

Basically, when memory seat A or B is selected, the mirror moves to various positions erratically and usually NOT to the preset position. Sometimes it moves only a very small amount and it takes continually pushing of the memory seat button to get it to finally move to the preset definition. Other times, the mirror moves a large amount to some bizarre position like slanted completely towards the car.

I have a dealership appointment but wondered if this might be as simple as pulling a fuse to reset a computer. Anyone know what fuse in the '05 Avalon might make sense to pull and try?

[retired00]

no problems on mine but I had another car with a similar oddity on memory seat/mirror. I would run the mirror manually full left, right, then up, down, then reset memory and it would cure it for a while.

[inov8]

The wiring diagram shows unswitched battery connected to the memory seat/mirror controller via 2 fuses:
"Power Window" - 25A - located below the instrument panel, left side (see owner's manual P380).
"ECU-B" - 10A - located under the hood, left side (see owner's manual P379).

I would try the Power Window fuse first.
After removing and replacing the power window fuse, the "express" functions must be re-initialized. Instructions are on page 41 of the owner's manual.

[inov8]

You might also have to re-initialize the power seat after removing and replacing these fuses. If it does not function properrly, do the following procedure:

(1) Using the seat switches, fully slide the seat forward, fully recline the seatback forward, and fully raise the seat cushion and headrest.
(2) Using the seat switches, fully slide the seat rearward, fully recline the seatback rearward, and fully lower the seat cushion and headrest.

[jeffcarp]

Thank you for your thorough advice. Unfortunately, it didn't clear it up. I pulled both the ECU-B and the Power Window fuses. It is hit and miss whether or not the driver's side mirror moves to the correct location when pressing the memory A or memory B button. In fact, the drivers mirror sometimes does nothing when pressing the memory buttons repeatedly and then may, after 6, 10, 15 pushes decide to move. Note that the passenger side mirror works fine.

Does this experiment narrow it down for you? Something bad in the mirror mechanism itself?

[inov8]

If the left mirror moves smoothly throughout its range with the manual controls, I would conclude the mirror itself is OK. In that case, I would suspect what Toyota calls the LH mirror ECU (electronic control unit), which is an electrical transceiver module mounted near the memory switches.

I think the system works like this:
When you press the memory buttons, a serial command code is generated and sent along a serial multiplex wire ("bus") to the body computer. The body computer, in turn, sends serial codes along that same bus to seat and mirror multiplex receivers (there is one in each door for the mirrors). There in turn drive the positioning motors.

Hopefully your dealer has eqipment to quickly diagnose the problem, has the replacement part in stock, and can restore operation in one visit.

Because one mirror works OK, I don't think a more drastic step (forced reset of the body computer) will be effective.

[jeffcarp]

Well, this morning, the mirror works as expected. The car sat in a garage that was about +45 degrees F all holiday weekend. Thinking back, this started to happen after a car wash when the temp was around +30 degree F.

It would make perfect sense that the something was iced up in the mirror except for the fact that I could control it manually without issue. Maybe some ice bridged across some wire terminals or something causing only the memory controls not to work on the mirror?

Any ideas?

[inov8]

It is possible that ice restricted, but did not prevent, manual movement of the mirror.
I do not know if Toyota employs relative or absolute position sensing for the mirrors; their training info indicates relative position sensing is used for the memory seats.

Relative position sensing relies on the computer knowing the previous location, then counting the revolutions of the positioning motors to determine when the new target position is reached. If mechanical motion becomes restricted, correlation to absolute position is compromised, and the system will attemt to recalibrate by trying to drive the mirror to the travel stop (as far as it can go in a direction), then counting from there.

This could explain the two conditions you described (limited motion and motion to an extreme position).

[jeffcarp]

I think you hit it on the head with your discussion of absolute and relative positioning. That seems to be exactly what is happening. I went through a car wash yesterday and nearly immediately after the problem started again.

Any idea what particular part might be getting wet to cause this malfunctioning?

[inov8]

I assume the local temperature was above 32F, so ice formation in the mechanism was unlikely this time. I've taken a look at the Avalon schematic for the memory mirrors, and it shows otherwise-unidentified 3-terminal positioning sensors (2 per mirror). This suggests to me absolute, not relative sensing, meaning my previous theory is suspect (a polite term for wrong).

Your new observation leads me to suspect water is seeping past a sensor seal and affecting the measurement. Here is what I would do next, to further pin down the cause:

With outside temperature above freezing, spray water equally into both mirrors. If you can readily reproduce the problem again, and it affects only one side, this knowledge will be very valuable to a service tech. Particularly so if described by you in writing.

However, if both mirrors now act similarly, they may simply not be designed to handle that amount of water exposure. Try to avoid spraying water direcly into the space between mirror glass and housing.

If the former occurs, you appear to have a valid warranty claim. You know what comes next.

Should you just orally describe the problem to the Dealer Service Manager, he/she will make some notes for the technician, but those notes will be but one of many written that day, may not be legible, and may represent his/her interpretation of what you described (so inaccurate). As a consequence, the Technician may not be able to reproduce your problem, and everything may test OK. Frustration all around.

Even if they do understand, the idea of replacing or repairing the mirror assembly may not be particularly attractive to them, because when they send the original part to Toyota, it may test OK, so Toyota will refuse to reimburse the Dealer for warranty replacement. They may simply tell you that the mirrors are not designed to tolerate immersion (a variation on "they all do it"). Your retort in this case would be to ask why only one mirror fails when they are subjected to identical conditions. This point should be made clear in your written description.

The Dealer will staple a copy of your written problem description to his request for warranty reimbursement, and consequently, Toyota will likely honor it. Thiis sets up a "win-win" for both yourself and the Dealer.

If they elect to replace the mirror, they will probably have to order one in your color. I doubt if these fail often.

[jeffcarp]

I sincerely appreciate all of your help. You have been great. I will be seriously concerned if the dealer attempts to tell me that a $36,000 Toyota can't go through a car wash in 35 - 40 degree weather. That might be an answer I'd expect from a GM dealer but not a Toyota dealer. I will summarize this discussion in writing and give it to them when I take the car in Saturday. I will let you know what I find out.

Thank you!