The CTS- coolant temperature sensor is indicating to the ECM-Electronic
control module that the engine has not reached proper operating temperature
or the threshold point where the ECM switches from open loop to closed loop
In open loop the ECM controls various engine functions such as fuel mixture
and engine timing using pre-programmed parameters that are stored in the
PROM- programmable read only memory.
After the engine reaches proper operating temp and all the sensors are
then the ECM switches to closed loop operation and begins receiving data
inputs from various engine control sensors such as TPS-throttle position
sensor, MAP-manifold absolute pressure, MAF-mass air flow, CTS.....,AIT-air
intake temp., etc etc etc
In a nutshell either the engine is running too cool or the CTS is faulting
causing the ECM to operate in closed loop or (limp home mode) on the early
C3-computer command control systems where i began learning EFI and computer
You've got to change your way of thinking when dealing with these systems,
sometimes i grab a beer and watch the Disney movie "Tron" when they start
testing my patience.
I forgot to mention that the 4x4 is a 1997 Silverado with a 5.7l F1 V8
engine with 125K miles on the odometer.
Used my ODB II code reader to troubleshoot a Service Engine Soon light.
It quickly returned the following.
Insufficient coolant temperature for closed loop fuel control
What does it mean?
According to your temp gauge, is it running as hot as it usually does or
does it seem to be running cooler?
Can't tell, since the truck belongs to my Navy son who was transferred to
Italy last October, I haven't driven it much until recently. My son told me
to sell the truck since he will be in Naples for the next 3 years. I noticed
the service engine light on when I drove it for about four miles just to
keep it in "shape". I'm not sure how long it has been on. I do know that my
son did not tell me anything about it when he dropped it off at my home.
I checked the coolant level and it was low. It took about a gallon of
anti-freeze to top it off.
I erased the service engine soon light and drove it for about 6 miles and it
Thanks for your help.
Found this url using a GOOGLE search
No mention of Vortec 5700 V8 engine
WHAT!?! You have a GM 3.4L LOWER INTAKE LEAK too!
So, your low coolant light came on for the second time in a week! You look
around and no external coolant leaks. You decide to check the oil. Oil cap
& PCV are coated with white sludgy crap. Guess where the the COOLANT went
... into the CRANKCASE via the lower intake manifold gasket!!!
In response to the overwhelming evidence I found while researching my own
vehicle, I have created this site to inform others of this Coolant-Oil leak
problem with the lower GM intake manifold gasket on late 3.4L V6 GM 199x -
200x Pontiac Montana, Chevy Venture, GrandAm, Alero, etc.
Visit this victims website and read the horror stories that have occurred
when coolant mixes with your crankcase oil: Shawn's GM-V6 Lemons
Here is another one. No mention of trucks however.
From: Teri (Original Message)
I just thought I would let everyone know that I have posted the following
on several AOL car care and repair message boards today. I have included
the petition link and am hoping more people will go and sign it. This may
help us all out. The peition needs to be submitted.
I have a 2000 Monte Carlo SS V6 3.8 with 52,000 miles on it. Car has been
very well taken care of. Always had oil changes when due, etc. Just had
to have upper & lower intake manifold gaskets replaced for a total cost of
$1,225.00. I am out of warranty and GM would offer no cost assistance. I
have spent hours searching different sites trying to gather as much info as
I can regarding other owners having the same problems. I am just amazed at
what I have found. It is very obvious from my research that GM is well
aware of the design flaw with their gaskets as they have manufactured an
"upgraded" part. If anyone out there is having the same problem, you may be
interested in visiting this site
http://www.petitiononline.com/GMcnsmrs/petition.html and signing the online
petition. There are over 2,300 signatures so far and growing at an amazing
rate. Hopefully there will be a recall someday and we can get our hard
earned money back!
Also, I am located in the Chicago area. Yesterday, I contacted several
local investigative news stations asking them if they would be interested in
doing an investigation and a story regarding this problem. I have also
filed complaints with the National Highway Traffic Safety Administration,
the Better Business Bureau and the Center for Auto Safety.
I have also written to Mr. G. Richard Wagoner, Jr. who is the President and
CEO of General Motors today and I am sending this letter certified. If any
one is interested in seeing a copy of this letter, email me and let me
know. I also emailed the letter to several different people at GM.
As soon as I hear anything that could maybe help us all I will let you
Hopefully, something will come out of all of this.
To: General Motors Corporation & The Better Business Bureau
We, the undersigned petitioners, General Motors' customers and/or
technicians who service GM products, do hereby give notice that we are more
than dissatisfied with the quality of the intake manifold gasket installed
in GM vehicles. As of April 10, 2002, there is a nationwide backorder of the
intake manifold gasket. At this time, is it not even known when the part
will become available. Being aware of this proves there is a serious problem
to be addressed. Because of apparent poor engineering, GM can not
manufacture replacements fast enough for all the vehicles in which they are
Intake manifold leaks can lead to any number of very serious, and
expensive, problems. While the part itself isn't costly, the labor to repair
it is very intensive, and has been quoted around $800 USD (give or take a
couple hundred depending on the vehicle). This is in addition to any other
costly problem(s) the intake manifold gasket leak may have produced.
We are demanding accountability from General Motors. A nationwide
backorder should be reason enough for GM to assemble a recall. We can only
hope that "the world's largest vehicle manufacturer" who "has been the
world's automotive sales leader since 1931" will stand up and claim
responsibility for a problem that is so prevalent among their vehicles.
Recalls should be mandated in all cases of incompetence, not solely when it
affects public safety.
While some of us have been "fortunate" enough to have this problem occur
within our warranty, there are many others of us that have had to pay for
these expensive repairs just after the warranty expires. Because GM has
refused to admit liability on this issue, we feel that this will be a
repetitive problem. Once this gasket has been replaced, and customers'
pockets drained, GM Service Centers everywhere can expect to see consumers
returning, for this same problem that hasn't been rectified due to a
designing flaw on GM's part. This error should have been corrected, not the
first time in for service, but before entering mass production in millions
Can one presume this is one way of keeping General Motors' patrons coming
back time after time?
Finally found some,
From: mdstine (Original Message)
I own a 1997 Silverado with the 5.7 litre (350 ci) V8 engine. During a
service check for hard starting the dealer discovered that it was leaking
coolant from the intake manifold gasket. While I have owned it for nearly 5
years it only has 41,500 miles on it. And, as was pointed out in the letter
re: the possible class action suit this is not a part that suffers from
wear. I have written a complaint to chevrolet and also recieved a half-off
deal along with some rhetoric about extended contracts. I am assuming from
the conversation I had with the service rep and this reply that this is
common in these engines as well. I will attempt to send my information to
the lawyer involved in the clase action inquiry.
A co-worker of mine has a 1997 Yukon with the same engine. He has had his IM
gasket replaced twice. He has about 100,000 miles on it. I will ask him to
add his name to the list as well.
From: Justin Sent: 1/25/2003 12:45 PM
I just found out that I, too, get to replace my intake gaskets on my
1998 Tahoe. Oddly enough, not 5,000 miles ago, I replaced the water pump,
had the coolant system flushed, and pressure tested, and refilled. I spoke
with a good friend of mine who also owns a 1998 Tahoe, and sure enough (or
oddly enough) he replaced his intake gaskets as well. My mileage is 74,000.
His mileage was 75,000. Cooincidince? This is like clockwork. We both
had our normal service, oil changes every 3,000, etc.
I've written a letter to the dealership, Classic Chevrolet, here in
Dallas, TX, to ask that they comp the labor. I've read that some
dealerships in Canada are doing this. After all, it's a $14.99 part retail,
GM KNOWS there is a problem, and apparently, after the research I've done,
it is almost a ceretainty that new intake gasket replacement is in the
future of most GM engines with the post 1996 Vortec V-6 or V-8 with the
similar cheap gaskets.
I'm pretty livid now, after the research I've done, to have been told
that this is normal wear and tear. Bull _____. I researched service
bulletins and recalls and issues with Ford and Dodge, and their intake
gaskets RARELY fail.
Fortunately for me and my friend, the coolant leaked to the outside,
not to the inside, according to the dealership. I'm not so sure I believe
them, as there is some engine noise now. Ok, I've done enough rambling, and
for sure, enough driving of GM products.
From: alumeye (Original Message) Sent: 1/23/2003 12:29 AM
I'm writing a letter to GM right now re: my '98 Olds Silouhette
that has misc. problems including a leaky intake manifold gasket. Was very
excited to see your petition; great work! As others, I'm curious to know
when/ if this petition is going to be sent off to GM? How many signatures
do you need? I just added the 1519th.
Earlier tonight I found this Technical Service Bulletin on this
02-06-01-014 APR 02 Intake Manifold (Lower) - Revised
...which sounds like it might be related to the problem many of
us are having with our GM engines. Does anyone know how TSBs work? Are GM
dealers required to do these repairs free of charge or at some discount?
Does anyone have access to the full details on this TSB? Looks like
Alldata.com is in the busines of selling the details.
From: Alyson ~Petition Manager (Original Message) Sent:
6/23/2002 5:27 PM
A gentleman who came across our petition has gone yet even
further than the petition. Mr. Hawkins had this common problem in his '98
Transport and decided to email a lemon lawyer. With the help of everyone
involved, this could lead to a class action lawsuit against General Motors.
Following you will find the text of his correspondence with the Lemon Law
Start of Mr. Hawkins' email
I have a 98 Pontiac Trans Sport that had an intake manifold
leak at 50,000 miles that caused coolant to leak into the oil. The cost of
the repair was about $650. My net research revealed this to be a very common
problem. For example see:
I think this would be an ideal case for a class action suit. I
threatened GM with a law suit and they offered to reimburse me 1/2 the
repair cost. I refused because they steadfastly refuse to acknowledge that a
problem exists with the intake manifold gaskets on this line of V6 engines
although the problem is well documented.
This is an excerpt from an email from a person in a similar
"I am having the same trouble with my 99 venture. I am also
just beginning my fight with GM. I am also building a website in regards to
these motors. I am sure you are aware that this problem is not just
affecting the vans, but also most cars with the 3.1, 3.4, and the 3.8 V6
engines. I understand from a friend who is the service manager at a Chevy
dealer, that they get them in all the time. He says that GM is in the
"denial" stage. They know that the plastic gasket is inferior, but, at
least for now, are refusing to deal with the problem. He told me that GM
went to the lowest
bidder and they screwed up the plastic mixture on the gaskets,
and they simply are not lasting, and the company that GM screwed that made
the first gaskets is now laughing in their face. He said there are bound to
be class action suits popping up everywhere. Unfortunately, he also said
that most people are just not realizing that the gasket should very rarely
EVER go bad. He told me prior to these engines, they never replace a intake
gasket unless they did head gaskets."
(end of excerpt)
What do you think?
Mr. Hawkins [full name & contact information withheld by me,
So it looks like you are right Doc.
I will have to have my friend John look at it.
Thanks again for your comments.
His stat might be fine, could be a variety of other things either causing
the engine to run cold or causing the PCM to "think" it's running cold. I'd
do some more simple diagnostics before I started throwing parts at it.
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