What is the second coolant temp sensor for? 1989 Cavalier 2.0 OHV/TBI HO
Necati
for (the one with two wires on the connector) on my 1989 Cavalier [ 2.0 OHV
engine (TBI HO Fuel system), NO A/C, No power steering ].
I went to a part shop a number of times and they don't seem to have it
listed at all. [they sold me Manifold Air Temperature Sensor when I asked
for the second temparature sensor, I was about to dip it into the coolant
if I did not notice the difference between the old and the new sensor]
Does the coolant sensor wit h two leads and is located an inch above the
another coolant sensor go to ECM? Why does it have two leads? (the first
sensor has one lead and it connects to TEMP light on the dash board)
I am asking these questions because my Electric fan seems to be never on
(except when I am testing for engine code)
By the way I am struggling with Check Engine light , code 13, which is O2
sensor, but I know my O2 sensor and its connection to ECM are OK).
And I got tired replacing parts without knowing exact source of the problem.
This weekend I replaced,
1-Oxygen sensor
2-PCV valve
3-EGR valve
4-Coolant temperature sensor (the one with single connector)
5-(Manifold Air) Temperature Sensor
in that order . The light is still on.
Any comments will be appreciated.
Necati
Chris Watkins
>
> Could someone please tell me what the second coolant temperature sensor is
> for (the one with two wires on the connector) on my 1989 Cavalier [ 2.0 OHV
> engine (TBI HO Fuel system), NO A/C, No power steering ].
>
> I went to a part shop a number of times and they don't seem to have it
> listed at all. [they sold me Manifold Air Temperature Sensor when I asked
> for the second temparature sensor, I was about to dip it into the coolant
> if I did not notice the difference between the old and the new sensor]
>
> Does the coolant sensor wit h two leads and is located an inch above the
> another coolant sensor go to ECM? Why does it have two leads? (the first
> sensor has one lead and it connects to TEMP light on the dash board)
>
One's a coolant temp sensor (to the ecm) and the other's a temperature
sending unit (to the gauge or light).
> I am asking these questions because my Electric fan seems to be never on
> (except when I am testing for engine code)
>
Some cars use a separate (third) unit called a coolant fan switch.
I am thinking the little cavalier takes info from the coolant temp sensor
and uses the computer itself to close the relay, instead of having a
circuit separate from the computer. Always fun to tell a customer that
they need a new computer, usually due to some damage caused by them
straight wiring the fan themselves. Sounds like that circuit is ok on
your car, though, given the fact that the fan is working during tests.
Replace the coolant temp sensor if it's not coming on by 220-225 degrees F.
> By the way I am struggling with Check Engine light , code 13, which is O2
> sensor, but I know my O2 sensor and its connection to ECM are OK).
>
> And I got tired replacing parts without knowing exact source of the problem.
> This weekend I replaced,
>
> 1-Oxygen sensor
> 2-PCV valve
> 3-EGR valve
> 4-Coolant temperature sensor (the one with single connector)
(this one only worked your light inside the car, I believe)
> 5-(Manifold Air) Temperature Sensor
>
> in that order . The light is still on.
>
> Any comments will be appreciated.
> Necati
Welcome to the joys of diagnostic work. You really need to purchase
a good manual for your car. A driveability manual, not a mechanical manual.
You are learning part of why we get paid to work on them ;)
When you get an O2 code, it could be the O2 circuit itself, gas in the oil,
bad air filter, bad fuel filter, bad fuel pressure regulator, vacuum leak,
water in the connector, connector wire chaffed or burned and rubbing to ground
or a power wire, or even the O2 sensor itself. Could be a few more things
that I haven't even mentioned, but aren't you tired of guessing yet ?
What sort of voltage is your scanner showing for the O2 circuit ?
Is it fixed high or low, or is it moving back and forth, but sluggishly ?
With O2 disconnected, place a wire inside the harness connector, ecm side.
Holding the other end of that wire in one hand, touch the other hand to
the negative battery terminal, then the positive. Did the scanned voltage
increase and decrease to max limits as you did that ?
Yes ? Circuit fine.
Sensor connected, induce a rich condition using your old propane enrichment
kit for setting carbs. Now induce a nice vaccuum leak by pulling the
vacuum to the pcv valve. Did the sensor respond immediately ?
If you don't have the scanner that lets you read live data, you'll
either have to break down and let somebody do a diagnostics for you,
or purchase a good scanner or a VERY good Vohm meter and learn how to use it.
--
Chris Watkins
<next two sig lines for rent>
<call 555-555-5555>
rm
>another coolant sensor go to ECM? Why does it have two leads? (the first
>sensor has one lead and it connects to TEMP light on the dash board)
most temp switches only have one wire (just turn on/off at set temp)
most temp sensors have two wires (send temperature signal to computer
or fan controller). I think GM uses the ECM to control the fan.
>I am asking these questions because my Electric fan seems to be never on
>(except when I am testing for engine code)
>
>By the way I am struggling with Check Engine light , code 13, which is O2
>sensor, but I know my O2 sensor and its connection to ECM are OK).
Some ECMs make a distinction between a bad o2 circuit and an 'out of
bounds' signal...
thus, in some cases an oxygen sensor 'code' may mean the signal is out
of bounds, not that the sensor is bad. weird signals may come from
the car running much too rich or lean (faulty or leaky fuel injector,
bad pressure regulator, etc).
Mark Morissette
>for (the one with two wires on the connector) on my 1989 Cavalier [ 2.0 OHV
>engine (TBI HO Fuel system), NO A/C, No power steering ].
One sensor controls the temperature guage or 'overheat' light on the
dashboard, and the second feeds coolant temperature information to the
ECM for engine management purposes.
>I went to a part shop a number of times and they don't seem to have it
>listed at all. [they sold me Manifold Air Temperature Sensor when I asked
Try the dealer if an aftermarket place doesn't have it, or you
continually get wrong parts.
>By the way I am struggling with Check Engine light , code 13, which is O2
>sensor, but I know my O2 sensor and its connection to ECM are OK).
>
>And I got tired replacing parts without knowing exact source of the problem.
>This weekend I replaced,
>
>1-Oxygen sensor
>2-PCV valve
>3-EGR valve
>4-Coolant temperature sensor (the one with single connector)
>5-(Manifold Air) Temperature Sensor
An 'o2' code doesn't necessarilly mean that it's a bad sensor, it can
also mean that it's sensing a problem in the engine that could likely
be a result of another problem.. It sounds like you may have spent a
great deal of money on unnecessary items.. Kind of like replacing the
battery when it's the Alternator that's at fault.
---
Mark, Oshawa, Ontario, Canada
Remove NOSPAM to respond via Email!
Send all spam to "send.sp...@home.com" - Promptly forwarded to www.spamcop.net! :-)
Necati
Thanks for the through response. It is just the info I needed.
Most of what you said makes sense. I could not understand some of the
diagnostics methods you described. I never owned a scanner. Where can I
get info on scanners?
I will change the coolant temperature sensor as soon as I get a chance. I
also noticed that fuel filter has not been replace din ages ( but the car is
running fine , except SES light comes and goes).
Do you think running engine SES light on (in warm-up mode of the ECM) is
bad for the catalytic converter?
It sounds like you are a professional car mechanic. And I appreciate the
hard work you people do. I hope, though, you excuse the following
comments from me:
My insistence on trying to solve the problem myself is due to
a)-curiosity/hobby,
b)- need,
c)- some bad experience with car repair shops.
I truly don't know a shop where I can trust that I will get a decent job
done at a reasonable cost. For example the first time SES light problem
occurred I took the car to a service station and they diagnosed it to be the
oxygen sensor. I OK ed them to replace it. Payed $105, headed home and the
light came back on.
I immediately took the car back. This time they said my computer is bad,
which I doubt is the case, and I declined it to be repaired there.
Anyways , thanks again for the answers.
Necati
Necati
Necati
Mark Morissette wrote in message
<380d111e...@news2.rdc1.on.wave.home.com>...
>---
>An 'o2' code doesn't necessarilly mean that it's a bad sensor, it can
>also mean that it's sensing a problem in the engine that could likely
>be a result of another problem..
>
Necati
Necati
Chris Watkins
>
> Chris,
>
> Thanks for the through response. It is just the info I needed.
>
> Most of what you said makes sense. I could not understand some of the
> diagnostics methods you described. I never owned a scanner. Where can I
> get info on scanners?
Find the name of a Snap-on, Mac, Or Matco tool dealer near you. You can
probably get the number from someone at a local shop, to call. The tool
dealer will probably set up a time for you to talk to his tech-tools guy,
if you're serious about going through with this.
Note that they are expensive pieces of equipment, but very valuable as
diagnostic tools. To properly diagnose the O2 circuit, you will either
have to get a good, user-friendly scanner like the Snap-on 2500, or learn
the system inside out through studying manuals and theory. Once you understand
the system forwards and backwards, then you can probably make do with a
high-end VOHM meter or even a lab scope. (less expensive items, but still
pricey)
What you have to be able to do is either be able to read the live data stream
from your ecm, or at least the voltage from the sensor itself, while connected.
You also have to have a very firm grasp on what you're looking for.
I guess I'm saying all that to say that unless it's worth it to you to spend
the money and time, I'd just take it to a shop for the diagnostics. They've
already spent the money and time learning it all and buying equipment :)
> I will change the coolant temperature sensor as soon as I get a chance.
If your car isn't running hot, it may not need replacing. Unless you have
the means to measure the actual temperature of the coolant while running,
you will have to have this checked at the shop, too, unless you just want to
replace it anyway. The fan will only come on around 220 degrees or so, and
I've seen that a even a few degrees higher on some cars. if you mean the
fan isn't coming on at all, even after sitting idling for a long time, then
you could need a new one. Of course it may just be a bad T'stat, too...
which could be stuck open, and causing a rich condition, as well as not
allowing the engine to get hot enough to trigger the fan.
> I
> also noticed that fuel filter has not been replace din ages ( but the car is
> running fine , except SES light comes and goes).
This should be a normal maintenance item... replace it at least every tune-up.
shadetree test is to remove it, and see if you can blow through it easily.
Of course remember the safety stuff... I don't need any lawsuits <G>
Neglected fuel filters are the number one cause of early fuel pump failure.
>
> Do you think running engine SES light on (in warm-up mode of the ECM) is
> bad for the catalytic converter?
>
Extremely bad. Raw fuel is the number one killer of Catalysts, bar none.
Engines running in open loop condition, extended WOT driving, racing the
engine on cold starts, bad air filters, excessive fuel pressure, bad plugs...
All those things are absolute killers. Whenever you finally get your car
repaired, break out the ole pyrometer, and check inlet and outlet pipe temps
on the cat. Expect the outlet to be drastically hotter than the inlet, or the
cat is not doing its job. (at least 90 degrees hotter outlet than inlet).
> It sounds like you are a professional car mechanic.
Well, fifteen years later, I'm a service manager.
I work hard, still, but the guys say I work hardest at trying to keep the
white shirts clean. Whatever... They weren't MY idea. I liked the old ones.
And I kinda miss turning wrenches every day, too. They keep giving me crap,
and I'll fire one of them to get my job back <G>
> And I appreciate the
> hard work you people do. I hope, though, you excuse the following
> comments from me:
>
> My insistence on trying to solve the problem myself is due to
> a)-curiosity/hobby,
> b)- need,
Nothing wrong with that. A) is what got me started, I'd say from the age
of 6 or so, when I was tearing apart my toys to see why they ticked.
My grandpa always told me back then, "learn how to put them back together,
and then you'll be doing something useful :)
B)is what actually got me into repairing autos. Bought my first car at 15.
Had to learn to fix it in the year before I turned 16, so I'd have a ride.
The start of my career. Of course I had the standard small engine experience
going from the time I was 12 or so. Had to keep the gocart going, yaknow.
> c)- some bad experience with car repair shops.
> I truly don't know a shop where I can trust that I will get a decent job
> done at a reasonable cost.
> For example the first time SES light problem
> occurred I took the car to a service station and they diagnosed it to be the
> oxygen sensor. I OK ed them to replace it. Payed $105, headed home and the
> light came back on.
> I immediately took the car back. This time they said my computer is bad,
> which I doubt is the case, and I declined it to be repaired there.
An oxygen sensor code is almost always the result of something else.
True, the sensor may be bad, but what caused it ?
It takes a very long time for most of them to die a natural death, as long
as the engine is kept in proper tune and good mechanical shape.
Sounds like an over-eager tech jumped the first problem he saw, and didn't
dig deeply enough. Of course, it could also be that the ecm IS bad, and
just happened to check good when he tested it. Hard to say, not being there.
He may not have went the extra mile. That test I told you of, with the probed
harness, and touching one hand to the positive terminal, checking voltage,
then the negative terminal, and checking voltage... would have checked the
ecm and O2 circuit to verify proper operation. The whole test is outlined
in a good driveability book for the car, and also in the troubleshooting
section of that scanner I told you about.
There are some good repair shops out there. Word of mouth is usually the
best way to find them. If you don't have benefit of word of mouth, sadly,
trial and error is the only way. If, instead, you're serious about learning
it yourself, then you'll likely need to invest in some proper books and
diagnostic equipment. Nothing wrong with that, it's just a bit expensive
considering how many times you're likely to use it at your home.
You'll probably never recoup your investment, unless you're lucky enough
to find a used scanner for a low price, that happens to cover your year
model already. (updates are in the $500 to $1500 range, depending on the unit
and the amount of time since the last upgrade)
Well, there's another rambling, crossposted newsgroup post. I'll shut up now.
Hope you get your problems straightened out, before they cause any new ones.
Take care, and good luck.
Steve Stanbach
Chris Watkins <umyt...@mindspring.com> wrote in message
news:380C4B31...@mindspring.com...
>
>
> You are learning part of why we get paid to work on them ;)
>
> When you get an O2 code, it could be the O2 circuit itself, gas in the
oil,
> bad air filter, bad fuel filter, bad fuel pressure regulator, vacuum leak,
> water in the connector, connector wire chaffed or burned and rubbing to
ground
> or a power wire, or even the O2 sensor itself. Could be a few more things
> that I haven't even mentioned, but aren't you tired of guessing yet ?
>
> What sort of voltage is your scanner showing for the O2 circuit ?
> Is it fixed high or low, or is it moving back and forth, but sluggishly ?
> With O2 disconnected, place a wire inside the harness connector, ecm side.
> Holding the other end of that wire in one hand, touch the other hand to
> the negative battery terminal, then the positive. Did the scanned voltage
> increase and decrease to max limits as you did that ?
> Yes ? Circuit fine.
>
> Sensor connected, induce a rich condition using your old propane
enrichment
> kit for setting carbs. Now induce a nice vaccuum leak by pulling the
> vacuum to the pcv valve. Did the sensor respond immediately ?
>
> If you don't have the scanner that lets you read live data, you'll
> either have to break down and let somebody do a diagnostics for you,
> or purchase a good scanner or a VERY good Vohm meter and learn how to use
it.
I like you computer diagnosis for the O2. Where did you get it from? I'm
asking because anytime I try something new at my school my teachers want to
know.
Chris Lawson
Necati wrote:
>
> Could someone please tell me what the second coolant temperature sensor is
> for (the one with two wires on the connector) on my 1989 Cavalier [ 2.0 OHV
> engine (TBI HO Fuel system), NO A/C, No power steering ].
>
> Does the coolant sensor wit h two leads and is located an inch above the
> another coolant sensor go to ECM? Why does it have two leads? (the first
> sensor has one lead and it connects to TEMP light on the dash board)
>
> I am asking these questions because my Electric fan seems to be never on
> (except when I am testing for engine code)
The one-wire is probably for the temp light on the dash, on or off
switch.
The other is probably for the computer which senses actually
temperature.
The computer probably controls the fan. If this sensor is bad, the fan
may not come on.
> By the way I am struggling with Check Engine light , code 13, which is O2
> sensor, but I know my O2 sensor and its connection to ECM are OK).
If the coolant sensor says the engine is warm when it isn't, that may
cause
an erroneous o2 sensor fault.
-Chris
Chris Watkins
>
> Chris Watkins <umyt...@mindspring.com> wrote in message
> news:380C4B31...@mindspring.com...
> >
> > Holding the other end of that wire in one hand, touch the other hand to
> > the negative battery terminal, then the positive. Did the scanned voltage
> > increase and decrease to max limits as you did that ?
> > Yes ? Circuit fine.
> I like you computer diagnosis for the O2. Where did you get it from? I'm
> asking because anytime I try something new at my school my teachers want to
> know.
Hmmm... I think that one is straight from a Chilton driveability manual.
You may want to peek inside a Snap On scanner, in the troubleshooting
section, though... See what the suggested O2 sensor tests are there.
I honestly can't remember. I'm just "assuming" you meant the part about using
your hand on the battery terminals to induce high or low voltage.
That's a real sweet test to make sure the ecm is working correctly
and that the entire circuit is ok, and... your body isn't going to conduct
enough current on this fragile circuit to possibly damage anything.