Door lock system causing aggravation
How can I find a wiring schematic and instructions howto access the connections for the locking/unlocking circuit for the doors on a 2006 Camry? The problem started slowly: once a week, then more often, until it totally stopped unlocking the three passenger doors. No problem locking, no problem unlocking the driver side door, or locking all doors on one click. I took the car to the dealership, and they confirmed the problem and said it would take a new part, costing $2,200, including labor. They also charged $170 to confirm what I told them about the problem. No troubleshooting was done. I phoned the dealership again, saying I just wanted the opening wire for the passenger doors connected to the driver side door wire, and have all the doors open on one click, just as I can lock all doors with one click. A later phone call advised me that a repair kit with two relays was available online, but the labor cost would be close to the new part quoted. Your advice and comments will be greatly appreciated. I am 88, on crutches and not able to do the work myself. — Volkmar S.
Oh boy, sometimes modern vehicles can make the most basic chores complicated! Your body electronic control unit (ECU) sends commands to your door lock actuators based on inputs from your key fobs and door switches. The driver’s door lock/unlock commands are a different circuit than the remaining three doors so that one click of the fob can unlock just the driver’s door and a second click unlocks the remaining doors. Power door locks are not that different from power windows, seats and mirrors in that the door lock actuators are tiny bi-directional motors. Applying a positive and negative command locks the doors and reversing the circuit polarity unlocks them. You indicated that the lock function works fine, which proves out all of the wiring and door lock actuators, leaving only the control unit, the body ECU, as the problem.
My hunch is the driver within the ECU (typically a cluster of four transistors, called an H-gate) is not up for the task of powering three door lock actuators simultaneously in the unlock direction. As mechanical systems age and become stiff to operate (the door lock/latch units) the electrical current needed to push them increases, and this is what eventually takes out the driver.
I think your best bet is to contact the person on eBay selling a $130 door lock repair kit for your car (search for “Toyota door lock fix” to find this).
He/she is apparently using a couple of relays to connect the three door circuits to the driver’s door circuit, with seven needed electrical connections. The relays are a good idea as they can deliver robust battery/fused power to the door lock actuators without burdening the existing driver’s door circuit excessively. It sounds like he/she has done a good job with clear instructions to make this a reasonably simple hookup, requiring perhaps an hour’s labor. A similar workaround could also be accomplished by a competent automotive electrician using their pro-database, perhaps $30 in parts, a half-hour of head scratching and an hour’s installation labor.
Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose, California. Readers may send him email at bradbergholdt@gmail.com; he cannot make personal replies.