MACS Service Reports - 2015 - JUN3

techinfo.toyota.com

he decided (correctly) that his own testing
put that diagnosis into question. The normal assumption with the symptom is that
the amplifier contains the intelligence, but he
switched the mode connector with the passenger side temperature control. When the mode
actuator started working, it made it clear that
the amplifier was fine and there was a problem with the connector. In fact, the diagram
provides the answer by labeling them "smart
connectors." See Figure 3. That tells you there's
a circuit board within them and it's that circuit
board that executes the reversal of each motor,
and it's obviously failed. The smart connector is part of a harness and the fix is to replace
it. Replacing an entire harness is high dollars
both in parts and labor, and therefore a tough
sell. But with no factory repair kit for a bad
smart connector, you have to get a new harness. Once you buy that, it would be awfully
risky to start cutting it for a reduced labor input.
We know that it's been done when the harness replacement itself is so onerous, maybe including a full-day dashboard R&R, but you'd
have to be awfully certain that the connector is
really all that's wrong, and that you make the
cuts very, very carefully so that if the new connector isn't the only problem, you can splice
it back into the rest of that new harness. Hey,
running an auto repair shop means making a
lot of tough decisions almost every day. ■

Figure 3: Toyota Avalon wiring diagram labels the wiring connectors as "smart connectors," which
tells you each contains a circuit board that can execute commands, in this case running the motors
forward and in reverse.

IS THE WIRING HARD TO REACH OR JUST HARD TO FIND?
Following is an example of a potentially very labor-intensive wiring harness operation, on a 2010
Ford Explorer Sport Trac 2WD with manual A/C.
Although the mode control is by vacuum actuators,
there was an obvious electrical issue. The technician could see that from the set of wiring diagrams,
there were two splices in the overall circuit, but not
much more that's obviously of interest than that.
See Figure 4. However, he did make some effective
checks to sort-of pinpoint the problem.
The original problem was a defective automatic
transmission shift interlock. The shop checked the
electrical side of it, including No. 20 fuse (10 amp)
and it was okay. So a new shift interlock assembly
was installed and the interlock worked. Next the
HVAC was turned on, but there was no electrical
HVAC functionality; no blower, compressor or temperature control. This time the technician checked
the wiring diagram and he went to the under-dash
Smart Junction Box. He saw that the No. 20 (10
amp) fuse was blown, and so he replaced it. It blew
again with operation of the HVAC. He removed the
HVAC control panel, opened it up and found a burn

June 2015

that had opened the circuit in the board, so he installed a new control head. When he tried to operate the HVAC, the No. 20 (10 amp) fuse blew again!
The technician replaced the fuse with a 10-amp
circuit breaker and he disconnected the yellow/violet wire at the temperature blend air door actuator,
checked it for a short and found none, just a normal
12-volt reading. He left it disconnected to keep it
out of the picture.
He next checked voltage at the No. 2 terminal
(another yellow/violet wire) at the Climate Control assembly and got a normal 12-volt reading and
no short. Following, he jumpered across the No. 5
(green/orange wire) and No. 2 (yellow-violet wire)
connectors at the Climate Control assembly and the
circuit breaker began to open, indicating a short,
but where? The green/orange wire circuit goes to
the accessories terminal (No. 15) of the Powertrain
Control Module, which is under the hood. The wiring harness goes through the firewall to Splice 213,
but where exactly is it?
If you check your electronic information system,
you should find linked charts that will take you to

MACS Service Reports

http://techinfo.toyota.com

Table of Contents for the Digital Edition of MACS Service Reports - 2015