"Dr. Gizmo"
By Phil Arendt
Pressure Sensor Sends Warning To Dash
Question 1
I have a 1996 Ford Crown
Victoria with a 4.6-liter engine that I have owned since it was new. It’s in great condition inside and out and
looks like new. I have always followed the
factory maintenance schedule and religiously change the oil and filter every
2,500 to 3,000 miles. It rarely has
given me any trouble and has 155,000 miles.
Recently, the service engine
light came on. I went to an auto supply
store to have the computer codes retrieved.
Only one code popped up. It’s
PO401. The parts man said that the DPFE
sensor probably is faulty but he wasn’t sure if replacing it would turn off the
light.
The car runs fine. The light is my concern. Do you think if I have the DPFE sensor
replaced the issue will be resolved?
D.W., email
Answer 1
Keep up the good maintenance
and much to your local Ford dealer’s chagrin your Crown Vic could roll past
300,000 miles.
The code indicates an issue
with the differential pressure feedback sensor.
It monitors the exhaust gas recirculation valve. It’s possible the sensor has a fault. It’s also possible the tube to the exhaust
gas recirculation valve is restricted or even clogged with carbon deposits
causing issues the sensor detects. It sends
a signal to the engine computer to turn on the dash light. Additionally, it’s possible the exhaust gas
recirculation valve has a fault and is the source of the trouble.
If you are an avid
do-it-yourselfer you could try to resolve the issue by replacing the
sensor. If not relay your experiences to
your favorite technician. It’s likely he
will perform some tests. He may even
attempt to resolve the issue by blowing air through the sensor as this
sometimes cures issues such as this. If
that does not work, he will need to do more diagnostic work. He might need to replace the sensor, tube or
exhaust gas recirculation valve if vacuum lines and electrical connections are
not causing the problem.
Fluid Attacks Engine
Question 2
Recently, my 2001 Oldsmobile Alero with 88,000 miles on the 3.4-liter
motor started running rough on a cold start. At first it was thought the cause was a leaky intake
gasket. That fixed the rough
cold start for a few days and kept the Service Engine Soon light off. Unfortunately, the light came back on and the
low coolant level light came on. Further
investigation revealed the cylinder heads were leaking and that they were
"eaten away" by the DexCool antifreeze. The cylinder heads and gaskets were
replaced at a cost of $1,600.
I've owned this car since new and have maintained it very well at
the same shop. I've had the coolant
flushed every other year because early on I heard how DexCool was junk. I recall a lawsuit against DexCool years ago
and had another G.M. vehicle that needed premature intake and water pump
repairs. I never saw a cent from the
suit. While failing gaskets are a well-documented
problem with General Motors engines, how could the coolant eat the heads? Is there any recourse against G.M. or the makers
of DexCool? G.D., Lakewood, IL.
Answer 2
Since I’m not a lawyer you
should contact the firm that handled the lawsuit. As I recall there was a class action lawsuit
filed against General Motors and DexCool that was settled around 2009. The suit was to provide relief to individuals
who experienced engine troubles due to the factory fill of Dex-Cool in the
engine cooling system. According to the
suit the coolant caused parts in the cooling system and intake manifold to
degrade. The coolant caused leaks or a
sludge developed that caused engines to overheat.
If you were a part of the
lawsuit you should have received notice from the law firm that was
involved. Generally, notification
letters are sent to potential parties to inform them of a lawsuit. Action is required by the party if they want
to participate in the suit. If you
signed on and participated in the suit you should have received updates and
notifications regarding the settlement.
Another cause for damaged cylinder
heads is electrolysis caused by poor ground connections. When there is a poor ground connection,
engine coolant conducts electricity.
This causes degradation of metals inside the engine. This results in leaks at gaskets and the
resulting damage to metal requires replacement of parts such as cylinder heads
and in some cases the engine block.
Engine Coolant Temperature
Below Normal
Question 3
Dear Dr. Gizmo. I have a 2011 Chrysler Town and Country with
22,000 miles on it that I bought new. It
has always been very slow to warm up. The
temperature needle never reaches the center point on the gauge during the
winter. On a 20-mile highway trip the
actual temperature indicator varies from 175 to 181 degrees. I learned this when I selected the vehicle
data display which shows actual engine temperature. The outside temperature was about 12 degrees
Last winter, I took it to
the selling dealer and requested that the thermostat be changed because it must
be malfunctioning. They did some tests
and said the thermostat is fine and did not need to be replaced.
Something is amiss because
the vehicle does not get warm although there is some heat after about six miles
of driving.
Just recently I put a 14 x
21 inch area of cardboard in front of the air conditioning condenser, like my
dad used to do in the old days. It seems
to speed warm-up, which makes me think that the thermostat must be opening
prematurely.
I am concerned because it is
uncomfortable and a cold engine uses more gas. I get about 16 miles per gallon in the winter. Also, a cold engine must not heat up the oil
the way it should and may be adversely affecting engine wear.
My warranty expires on March
29, 2014. Is there anything that I
should or could do about this situation?
C.W., email
Answer 3
Please remove the
cardboard. It could cause the engine to
overheat which could cause severe damage to the engine.
As for the thermostat and
engine coolant temperature, on a frigid day it may take 10 miles of travel
before an engine reaches full operating temperature. On really frigid days such as we just
experienced the engine may not reach full operating temperature. Plus your minivan has a lot of interior space
for the heater to warm up. Not only does
the heater need to heat air it must heat all interior parts such as seats and
trim. Also vehicles are not insulated
like homes so a heater works extremely hard to warm metal and interior trim.
Having said all of this, it
does appear that the engine is not heating to its full potential. Since your dealer says it is operating as
designed and will not replace the thermostat under warranty your recourse is to
have another dealership look into the issue.
Tests might find the first dealership misdiagnosed your concern and a
new thermostat will be installed. It’s
also possible cooling fans turn on too soon due to a faulty temperature sensor. Additionally, it possible the heater is not
functioning as designed. That needs
testing as well.
If another dealership agrees
with the first and everything is operating as designed your option may be to
pay to have a new thermostat installed.
Liftgate Fails To Open
Question 4
The automatic lift tailgate
in my 2011 Chevy Suburban will not unlock in cold weather. I have tried holding the switch buttons in but
to no avail. After the truck warms up, the tailgate might work, but not
always. This becomes a problem when you need to get into the back for
groceries, etc. My dealer says the cost to repair begins at $85 and can
go as high as $450. Is there something I can do, such as a lube, to get
the tailgate to work properly in cold weather?
J.O., email
Answer 4
Before the dealer has their
chance to fix the issue, try lubricating the weather stripping with silicon
grease. A thin coat on the strip might
do the trick.
Also, apply a spray
lubricant to the latch assembly. Silicon
grease and spray lubricant are readily available at auto supply stores.
If these suggestions do not resolve
the issue your favorite shop might need to replace the latch and or motor
assembly. It’s also possible the module
that controls the system needs reprogramming but the latch and a sticky weather
strip might be the cause of your concern.
Some Diagnostic Equipment
Not Fit For Job
Question 5
The battery died in my 2002
Mercedes-Benz C320. After jumping it I
went to a repair shop where the mechanic determined that there is a high draw
on the battery that causes it to die when the car is parked for more than a
day. The mechanic says that it might
take several hours to determine and repair the cause of the draw. He also said that if a module has failed his
equipment might not be capable of programming it. He suggested that I take the car to a
dealership or shop that specializes in Mercedes repair.
I really don’t want to take
the car to a dealer and I can’t find a shop near me that specializes in my
car. If my present mechanic can
determine what causes the problem with his test equipment, why can’t he program
a module? D.B., email
Answer 5
There are different strategies
to approach an excessive draw on the battery but the major issue in your case
is whether your technician’s computer scan tool is capable of doing all the
work necessary to complete the job.
Since your technician suggested taking the vehicle to a dealership or
specialty shop, he understands the limitations of his diagnostic tool.
There are a wide variety of diagnostic
scan tools in the market independent repair shops use. If your shop specializes in General Motors
vehicles they probably have a scan tool specific to that manufacture and a
generic tool for other brands.
Scan tools are expensive and
a shop tool budget does not allow for equipment purchases unless they repair a
large number of a specific manufacture.
A shop that specializes in Chryslers will likely have the original
manufacture tool that performs all the needed procedures to fix that
brand.
Most shops utilize generic scan
tools that have software to repair a wide variety of vehicle makes but because
of this the software has limitations that prevent a tool from doing some
repairs such as programming a computer module in some make cars. Some generic tools are specific to European
vehicles, some specific to domestics and others for Asian vehicles. Then there are some that allegedly can handle
all makes and modules. There just is too
much information programmed into all the different make vehicles for a tool to
handle. It’s almost impossible for a
tool specifically designed for one auto manufacture to handle all the
processes, changes and updates that are a daily occurrence.
A dealership or independent
shop that specializes in your vehicle will have a computer scan tool that is
specifically developed to perform all the functions necessary to repair your vehicle. Your shop technician made the correct
decision to suggest a shop that specializes in your vehicle. Chances are greater that a shop with the
proper equipment will be able to do everything necessary to diagnose and repair
the issue without any guess work. More
often than not guess work means higher repair costs. You definitely do not want to pay more for
less.
New Part Might Be Cause Of
New Problem
Question 6
I love my 2007 GMC Arcadia
but in the last two months it’s been giving trouble. In November a vent solenoid went bad. A few weeks later the brake booster needed
replacement. All was good until just
before Christmas when the check engine light turned on again. Since then I’ve taken the car back to my shop
twice. As of yet they haven’t been able
to determine the cause of the light.
During the first two shop
visits a mechanic determined that the fuel mixture was lean. He’s tested the gas to see if there is too
much ethanol. He also has checked for
air leaks in the exhaust and intake manifolds.
He’s used a couple of different methods to determine leaks. One was smoke and another was spraying
something on parts but neither method located any leaks.
My shop wants to do more
tests. The mechanic wants to drive the
vehicle for a day or two with test equipment connected but I really need
it. Except for the light, the vehicle
runs fine. Do you have any
suggestions? K.M.K., email
Answer 6
Perhaps it’s time to dump
the vehicle and buy a new one. All
kidding aside, it appears your technician is on the right track as tests
indicate a lean fuel mixture. Also,
since tests have not found leaks at the intake or exhaust manifolds it’s time
to take a step back and look for other causes such as leaks at vacuum lines,
hoses and fittings. It’s also feasible
there is a vacuum leak from the recently installed brake booster. Since the troubles began shortly after that
part was installed it might be a good idea to look at that first. After all more than likely your technician
has already thought about leaks at vacuum lines and perhaps dismissed the
possibility that the new booster is the cause of the issue. If it is, repairs should be covered under a
warranty.
Thank you for all the 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@hotmail.com. 01/13/2014 ® DR. GIZMO © 1989 - Present
