1. Auto 131 Lab Experience Report
Part 1: Vehicle Information
Student name(s):
Eddy Torres
TJ Mathews
Vehicle year, make, model:
Toyota Camry 1992
Customer’s name & repair order number:
Karlee Larsen ­ 9354
Customer’s concern(s):
The car will not start. Also the doors will not lock and nothing happens when the key is turned.
Part 2: Documentation
Document the steps you took to diagnose and repair the vehicle—in the order that you did them.
Write every step—even if you made mistakes and now wish you would have done it differently.
Begin when you picked up the keys, end when you returned them. BE DETAILED & INCLUDE
PHOTOGRAPHS!
Since the customer had their car towed to
campus, we had James help us with the
tug to pull the vehicle into the Ag shop.
Once inside, we started off by verifying
the complaint and just like the customer
said, the car didn’t start. We noticed right
away that there was a clicking intermittent
sound coming from the back of the dash
and the dash lights were blinking very
dimly. The customer told us that if we
disconnected the battery and waited a few
seconds and then reconnected it again the car would start. We tried it and it worked just like the
customer said. We drove around and there was no apparent problem. When we came back to
the shop, we decided to try to find the reason why the car did not start before. We then tried to
find what triggers the system to not start, so we started testing different things like unlocking the

2. door with the key, locking the door then unlocking it from the inside, wiggling the door wires,
turning on and off the headlights, among other things. From our testing we found that whenever
the doors were locked and then unlocked, the clicking sound would be triggered, and the car
would not start until we connected and disconnected the battery again. We came to the
conclusion that it was the anti­theft system what was causing the problem. We thought that
maybe a sensor in the door was sending a wrong signal to the control module, making it think
that the car was being stolen, or perhaps it was the anti­theft module itself or one of the cables
that was not working.
We decided to print a wiring diagram for the anti­theft system
and to narrow the problem just like we have done to the other
vehicles we’ve worked on before, but after taking a closer
look we found that the vehicle had an aftermarket anti­theft
system. Because it was aftermarket, we knew that the
original wiring diagram was not going to be very useful
because we didn't know how the previous technician installed
it. Trying it’s location, we were able to discover the system
along the firewall of the car on the drivers side. We located
the system and realized that the wires ran all over
underneath the dash. To verify that this was really the culprit
of the complaint, we decided to create an open in the circuit
to disable the anti­theft. In theory, if the anti­theft system was disconnected, then we should be
able to start the car with no problem. We found two fuses
underneath the dash that were connected to the anti­theft
module. It was evident that they were not installed
originally by the manufacturer, so we decided to
disconnect them to create the open circuit.
Just like we thought, the car started right away and
locking or unlocking the doors did not affect the starting
system. We asked Brother Schmalle for his advice. We
wanted to know whether we should leave the system
connected without the fuses or to completely remove the
system and resolder the wires. We concluded the best

3. option was to call the customer and ask if she wanted the system to be removed or left in the
car. We called her and she wanted the anti­theft system to be completely removed from the
vehicle.
We proceeded to start removing the wiring harness for
the security system. We started off with removing some
of the kick panel underneath the steering wheel to gain
better access to all the wires. We began by removing
the control box of the anti­theft. We then proceeded to
follow the wires that came off of the box and where they
went. When we came to the first wire we realized that
the wires were not soldered together, rather whoever
installed them just stripped a piece of the original and
then wrapped the new wire around the old wire with
electrical tape. In order to fix these correctly, we had to
find each one of the wires, cut them, solder them to
where they were supposed to be, and cover them with
heat shrink to ensure proper installation.
We went ahead and got the soldering gun, solder,
heat gun and billed out of omnique some shrink tube
to begin our repair. We had to locate all the cables that
were connected to the anti­theft system before we
started cutting and removing. It took us a while to find
all of them, but once we figured out where they were
supposed to be connected, it was just a matter of
being patient while connecting all of them back
together. We started to repair the wires one by one
first by making sure we had the wires stripped back
enough to allow a good solder. We heated the wires
with the solder touching it on the other side until it
melted and created a bond between the wires. The
smaller wires melted the solder a lot faster than the
bigger wires. After we let the wire cool we moved the piece of heatshrink over the soldered spot

4. and used the heat gun to shrink the piece tight to the cables. After doing this to all of the wires
and making sure all of the connections were in
the right spot, we tested all of the circuits to make
sure everything was working properly. We were
very excited when we finally removed the
anti­theft system and the car started right away.
We were a little nervous because there were lots
of cables that needed to be disconnected to be
fixed and we needed to make sure not to cut the
wrong ones and to connect them in the right
place. Finally, once the repair was verified, we
billed out the vehicle, cleared all the errors in
omnique and called the customer to pick up the
vehicle.

5.
Part 3: Reflection & Analysis
∙​ ​What parts of this process went well?
The overall diagnosing of the problem went well, as well as actually being able to get into the
vehicle to remove the aftermarket security system.
∙​ ​Which steps were most critical in your diagnosis process?
The most critical step was to test whether creating an open circuit in the anti­theft system would
allow the vehicle to start. Removing those fuses confirmed our diagnosis of a faulty anti­theft
system.
∙​ ​What kept you from being as effective as you could have been?
We wanted to try and repair the security system but since we did not have a wiring diagram we
were not able to complete this and ended up just removing the whole security system.
∙​ ​Now that you can look back on how this project unfolded, what would you like to do
differently next time?
Everything went very smooth. It was just a little scary when we saw so many cables mixed
together. It took us almost one entire lab day to locate all the wires the needed to be removed
and soldered together. But even though it took us a little longer than a professional technician,
We were able to correctly diagnose and correct the problem the customer was complaining
about.