"Dr. Gizmo"
By Phil Arendt
Getting The A/C Ready For Summer Heat
Question
1
The
air conditioning in my 2004 Chrysler Concord is not working. I took the car to my local repair shop where
a technician performed tests. He did not
find any trouble codes in the air conditioning computer. He said the system has plenty of Freon and
that it should work. He does not know
what is causing the problem, but he does know that there is nothing wrong with
the compressor. He says the compressor
engages when he forces to turn on. At
this point he will charge by the hour for his diagnostic work. He is not sure how long it will take to find
the cause of the trouble.
I
have to get this fixed before hot weather returns. Do you have any suggestions? A.N., email
Answer
1
This
may be a case where aftermarket diagnostic equipment software is not
sophisticated enough to find the trouble.
If you have a long and trusting relationship with your technician ask
him to consider voltage tests of the temperature sensors. These sensors react to temperature by
changing voltage in the system and turn on the compressor. He might find one of them is not functioning
within specifications. If so,
replacement of the faulty sensor should return normal function system.
If
you are not comfortable with your present repair shop consider taking the
vehicle to a dealership where odds are greater manufacture specific diagnostic
equipment will perform system tests that will find the cause of the trouble.
Power
Steering Affected By Debris
Question
2
The
power steering in my work truck intermittently does not work. It is a 2007 Ford E150 with a 4.6 engine and
57,000 miles. I checked the fluid level. It is fine.
The belt is tight and in good condition.
The
power steering can be working just fine when suddenly it becomes stiff and I
hear a buzzing sound from the pump. I
can drive for days without any problem.
Then for whatever reason I can be driving along without any problem and
the trouble surfaces.
Do
you think this is caused by a faulty pump or is there a valve or something
sticking? Would flushing the system fix
the problem? G.N., email
Answer
2
This
is unusual. Generally, a power steering
pump works fine or it doesn’t work at all.
The symptoms you describe point toward restricted flow of hydraulic
fluid. It is possible something is
blocking the flow of hydraulic fluid to the pump. Perhaps there is a foreign object floating in
the reservoir that occasionally blocks fluid to the pump. If this is the case suctioning the fluid or
removing the reservoir for cleaning may remove the object that causes the
trouble.
Flushing
the system might cure the trouble but I’m more confident removing the reservoir
for examination and cleaning is the correct approach to this unusual
condition. Who knows what happened but
maybe something dropped into the reservoir when someone checked the fluid level
or topped it off. Ask your favorite
technician to consider this theory when you take the truck to a shop.
Technical
Service Bulletin To The Rescue
Question
3
The
check engine light is on in my 2003 Nissan Altima. It has a 6-cylinder engine and 75,000
miles. Sometimes when I start the car it
runs fine and the light is off on my dash.
Sometimes when I start the car it starts fine but as I am driving the
light turns on and the engine idles too fast or the idle slows and the engine
stalls.
I
took the car to my local repair shop.
They found two codes. One was
PO507 and the other was U1000. A
mechanic checked for air leaks in the engine and tested a throttle
control. He said there are no air leaks
and the throttle control passed tests and is functioning normally. He says there is something wrong in the
wiring or there may be a faulty module that causes all the trouble. He says it may take a day or more to find the
trouble.
I’ve
never had a car with such a problem.
Does this make sense to you? Do
you have any suggestions? T.K., email
Answer
3
Thanks
for providing the trouble codes. PO507
is an indication of possible air leaks or faults in the throttle control
actuator or related circuit. Trouble
code U1000 relates to a problem in the circuit in the controller area network
or CAN. Your car is computer controlled
with computers and computer modules placed just about everywhere a design
engineer can place a module but don’t despair.
A
check of technical service bulletins found a lengthy bulletin that addresses a
CAN communications circuit problem. This
may be the key in finding the fault in your car. If your technician has not already done so,
ask him to look up bulletin NTB06-009a.
The procedures outlined in it may be just what he needs to troubleshoot
the condition. It deals with cleaning
and securing several ground connections in the circuit that are in the dash and
engine compartment. It is a big job and
will likely take several hours to accomplish the task. If his shop is busy he may need to divert
attention to other customers while he is working on your vehicle so plan to
leave the car in his hands for more than a day.
Code
Signals Troubled Transmission
Question
4
When
I drive more than 30 minutes the check engine light turns on in my 2003
Cadillac DeVille. When the light turns
on I do not notice anything wrong or unusual about the car. It starts and runs fine.
I
confided in a friend who is knowledgeable about cars. He says it is likely one of the oxygen
sensors is failing. He told me to take
the car to an auto parts store to have codes retrieved from the system. I did and the partsman found code 741. He said there is something wrong in the
transmission. My friend told me to take
the car to a transmission shop to have the problem repaired.
The
transmission seems to be working fine.
Will continuing to drive the vehicle cause harm to the
transmission? N.B., email
Answer
4
Automatic
transmissions are very complex machines that can suffer severe damage from the slightest
malfunction. Consider taking the vehicle
to a repair shop as a precaution.
Diagnostic
trouble code PO741 retrieved by your partsman does indeed relate to
transmission trouble. It refers to a
failure of the torque converter clutch.
The code means there could be a problem in the torque converter or
problems in the circuits, solenoids and valves in the transmission that control
the torque converter clutch.
If
your vehicle has traveled over 100,000 miles it is possible it is time for an
overhaul but repair to circuits, solenoids and valves may not require removal
of the transmission from the vehicle. If
it is determined the torque converter needs replacement the transmission does
need to be removed to access the part.
Let’s hope faulty wiring is the cause of the condition as this is the
least intrusive repair.
Hummer
H2 Not Humming Along
Question
5
At
times the 6.0-liter engine in my 2005 Hummer H2 will not crank when I turn the
ignition. Also, sometimes the ignition
key binds and sticks when I turn it to start.
These two problems can occur at the same time or independently. When the engine does not crank I turn off the
ignition and turn it back on and the engine usually cranks and starts within
three turns of the key. If the ignition
key binds I can’t turn it to start the engine.
I might have to remove the key and stick it back in two or three times
before the ignition turns to start.
What
causes these problems? R.S., email
Answer
5
It
appears there are two different problems.
To repair the ignition key problem, removing, cleaning and lubricating
the lock cylinder might be all that is necessary. Over recent years several General Motors models
have had issues with ignition lock cylinders and the cleaning procedure has
cured the binding problem. If it does
not, it might be time to replace the lock cylinder or maybe the ignition switch.
As
for the engine not cranking to turn over and start, this too may be a simple
condition to cure. Some Hummers had
issues with the battery terminal bolts coming loose. Check the terminal cable connections. They might be dirty, corroded or loose. If these conditions exist, remove the cables
from the battery terminals and clean them. Additionally, it might be necessary to replace
the bolts if they have been attacked by corrosion or the threads are broken or
striped. Once the terminals on the
battery and cables are free of any dirt, grime and corrosion, reinstall the cables
nice and snug.
Avoiding
Repair Shop, Free Repairs
Question
6
This
morning I was pulling into my driveway in my 2009 Buick Enclave when the engine
stalled and would not restart. The
instrument lights turn on when I turn the key to start and the engine cranks
but it won’t start. The power windows,
seats and radio all work fine so I know there isn’t a problem with the
battery. Also, the gas tank is nearly
full.
I
checked all the fuses in the passenger and engine compartments. All the fuses except a fuse marked ECM1 are
okay. I replaced the fuse and attempted
to start the engine but it still would not start. I checked the fuse again and it was
blown. I touched the computer in the
engine compartment and it felt hot.
My
vehicle has 56,000 miles and a 3.6-liter engine. I don’t want to go to a repair shop if it is
not necessary. Do you think there is something
shorting out in the engine compartment computer? Can I purchase a computer from General Motors
or auto parts store without having to go to a dealership or repair shop? Is there something else I should look
for? N.G., email
Answer
6
Wow,
you must have had a terrible experience at a repair shop not to want to have
your vehicle towed to a shop.
Certainly
there could be a short circuit in the wiring to the engine control module
instead of a short within the module itself.
However, a hot module is a clue there might be trouble within the
unit.
As
for purchasing a module, you can’t purchase a unit directly from General Motors
but you can purchase it through one of the franchise dealer parts
departments. Additionally, you can
purchase a module from an auto supply store, but I think you should reconsider
your position about not taking the vehicle to a repair shop especially to a
dealership. With only 56,000 miles and a
few years of use your wheels should be covered under the factory warranty. If so, you won’t have to go through the
hassle, expense and guesswork trying to determine the cause of the trouble and
repairs should be free of charge.
Give
it some thought. Call a dealer or
General Motors Customer Service to discuss the matter. You can find the phone number to GM Customer
Service in your owner’s guide. Also,
your owner’s guide explains the factory warranty. If you take your vehicle to a dealership all
concerns may be resolved to your satisfaction and your car will be repaired
without scraping a knuckle or spending a dime.
Thanks
for all of your great questions. Dr.
Gizmo can’t wait to answer more.
Phil Arendt is a columnist, consultant and
A.S.E.-Certified Master Technician.
Readers may send questions to Dr. Gizmo at P.O. Box 548, Cary, IL. 60013
or e-mail address drgizmo@drgizmo.ws. 4/20/2012 ® DR. GIZMO © 1989-2012
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