How a Simple Fix Solved Problem With Sienna Sliding Door System
After working on a few [Toyota] Sienna vans with the dual power sliding door system, I have found new meaning to the old Toyota sales slogan, "Oh, What A Feeling ... Toyota!"
The Sienna's main system components include a main on/off switch and right and left control switches. There are separate right and left sliding door motors and control units in the rear quarter panels. The motors have internal revolution sensors that produce square-wave signals as the motor moves, and electric clutches that are energized to engage the motor to the drive mechanism. The doors slide forward and backward on their tracks via drive cables. Each door has a lock release actuator motor to pull the door to a latched position and to pop it open.
Each door has two latches, one in the front and one in the rear. The lock release actuators have internal position switches to indicate when the door is in the fully latched and half-latched position. The rear latches have position switches on them as well. The lock release actuators get energized through sliding door contacts when the door is in the latched or half-latched position. These contacts do nothing once the door is opened. During normal operation when the door switch is pushed momentarily, the lock release actuator releases the latches and pops the door open and then the drive motor pulls the door open. With the door open, another push of the button slides the door forward, making contact with the sliding door contacts. Then the release actuator pulls the door into the latched position. It is a lot like a garage door opener; it even stops if it gets jammed and then reverses direction.
The control unit knows it is jammed when it sees the revolution sensor slow down sooner than expected. A common problem is that the doors do not operate after the battery is disconnected. This happens when the control unit loses its memory. The fix is to re-initialize the system. There are technical service bulletins (TSBs) that explain how to re-initialize the system. But if that doesn't work, then what next?
I took a call recently on a 2001 Toyota Sienna that would not re-initialize on one side. The door would open but that was it. When the button was pushed to close, it would move a couple of inches at a time and then would lock up and quit working. If battery power was disconnected, it would reset but it would still only open and then the warning light would remain illuminated. The tech tried unsuccessfully to retrieve a code; the light just stayed illuminated. At this point, a flow chart directed us to replace the control unit, but something didn't seem right about that.
We decided to check pin voltages at the control unit to verify the inputs were all correct; however, the factory pin voltage chart was incomplete. Most of the inputs are open or closed switches to ground that have a reference voltage with the switch open, and zero volts with the switch closed. The control switch input, power and ground were good but there was only one switch for both open and close - we expected two. Question: How does the control unit know if the door needs to be opened or closed with only one control switch and nothing to tell the control unit that the door is open? Answer: This is the reason it has to be initialized.
Why won't this one initialize? The first step of the initialization process is to push the button to open the door, wait three seconds, and then push the button again to close the door. Though this process opened the door, it wouldn't close it. It was as if the control unit didn't know the door was open. I asked the tech to check the revolution sensor, thinking that the control unit didn't sense the motor turning but found it had a good square-wave signal while the door was opening.
The rear latch switch was the main input to indicate the door was opening. The pin voltage chart didn't indicate what the latch switch should do, but a TSB I found indicated that the switch should pulse to ground twice as the door pops open and again when it latches shut. This switch did not change at all - it just stayed at reference voltage when the door popped open. Aha! The sliding door contacts must have baby formula on them! The tech checked, but they were clean.
The fix was the rear latch switch itself. After cleaning the rear latch assembly with some contact cleaner and exercising the latch several times, the switch started pulsing to ground. With the rear latch switch operating, we tried the initialization procedure again and it worked this time. That was all it took - simply cleaning a micro switch on the rear door latch; we didn't even have to take the door panel off.
If you run across a similar problem, save some time and check the rear latch switch first.
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