This is a 6 cyl SFI model. I'm trying to figure out how to do a basic
diagnostic on this car. I know with Most GM's of the early 90's, you
can short the pins A and B of the 12 pin connector under the dash. Then
turn the key on, and the engine light is supposed to blink indicating
any error codes.
I found the 12 pin connector. Problem is, only 3 pins actually have
wires running to them. There is no connection to the B pin, a nd
therefore, no way to short pins A and B
Here is a picture of what I am talking about at.
I also found a connector under the hood. This is a 10 pin connector with
9 actual connections..
You can see this one at.
Thanks for the info! I'm guessing that one of those cheap code readers
found in auto parts stores will not work with this system? or am I wrong?
Also, I am trying to verify that the ECM is actually turning on the
radiator fan when it is supposed to.. I've ran the car idle for over 20
minutes, and the fan does not come on. The fan does work, however when
connected directly to a 12v power source.
Neil Nelson wrote:
No, they won't work either (they basically are just a jumper for those two
pins, and yes, that does mean that they are, in fact, a complete ripoff)..
As far as the fan, what temperature is the gauge getting up to (if it has
one)? The fan doesn't generally come on until the temperature is getting
close to the overheating range.
Robert Hancock Saskatoon, SK, Canada
To email, remove "nospam" from firstname.lastname@example.org
news:_DMfb.19127$, that does mean that they are, in fact, a complete
I would have to agree. My 94 Grand Prix does the samething. If the fan isn't
coming on though, I would recommend looking at the relays for the fan, and
make sure they aren't bad. Normally using a known good relay is a good test.
Since the cheap code readers are nothing more than a jumper
and a blinking light, you are correct.
If one knows how the cooling fan is controlled, it is easy
enough to simulate the conditions under whiich the fan
should come on.
If the cooling fan relay is controlled by the ECM according
to the coolant sensor voltage, disconnecting the coolant
sensor and jumpering the pins will simulate a hot sensor
reading and should turn the fan on.
(note, this -will- set a coolant sensor trouble code, but
will not harm anything)
If the cooling fan relay is controlled via a separate
temperature switch/relay not connected to the ECM, grounding
the lead to that switch will simulate a hot sender reading
and should turn the cooling fan on.
GM cooling fan come on at around 230*F, so idling for 20
minutes is not always sufficient to generate enough engine
heat to verify proper operation.
The temp gauge on the dash has not worked for a long time in this car.
(This isn't my car. )
I'm not able to find the Coolant Temp Sensor..
However, if this is not functioning correctly, I should get a "check
engine" light on the dash, correct? And if it is working correctly, and
I am overheating, I would get a "Temp" light on the dash, right? So if
I don't get any lights, it means it should all be functioning correctly.
I did notice one thing.. If i'm using an almost dead battery in this
car, the fan comes on as soon as I turn the ignition switch. Is this
some sort of fail safe mechanism in case the coolant temp sensor isn't
getting enough voltage?
Neil Nelson wrote:
Is water supposed to boil into the secondary tank before the fan stars?
Water was bubbling into there like 2 or 3 minutes before the fan
actually turned on. I opened the secondary tank, and the steam almost
burned my thumb...
Are you using straight water in the cooling system?
Not a good idea...
Anyway, after 23 years of dealing with GM frontwheel drive
applications, most if not all of which had at least a 50/50
mixture of antifreeze and water, I'd have to say no, there
should be no boiling or bubbling of coolant into the
overflow tank prior to the cooling fan turning on.
You could merely have a radiator cap that isn't holding
pressure as it should (easily tested), a blown head gasket,
a thermostat that isn't opening at the proper temperature, a
faulty coolant temperature sender that isn't signaling the
fan to come on at the correct temperature.
You should have the problem checked out by a professional to
avoid serious mechanical problems and to avoid further
chances of personal injury.
I'm using a 50/50 antifreeze/water mix.
I think I might wire the fan so it turn on when the ignition is on
temporarily (preferrably using the fan relay) until it can be taken to
professional. I am going to look for the fan relay tomorrow when it is
daylight, but just in case I can't find it, where should it be located?
There is a line of 3 relays that look the same on the passenger side
near the radiator. Also where is the coolant sensor supposed to be
located? I dont mean to be asking too many questions, but that's one
of the ways I learn. Also, I don't have a book for this car.
Neil Nelson wrote:
Okay. Your original question about "water boiling" into the
recovery tank was a bit misleading...
It is one of the three that you see on the PS of the
radiator support. To tell which of the three it is, look at
the wiring color and compare it to the wiring that goes to
the cooling fan. You're looking for fairly fat wire that
matches what feeds the fan motor.
Under the throttle body, near the thermostat housing, it's a
two wire connector one wire being yellow, the other black.
There's nothing you can do to the coolant sensor circuit to
make the fan run constant without creating other havoc with
the EFI system.
You should get a book. preferrably the factory manual if
you're going to attempt repairs or modifications.
I replaced the coolant temp sensor. Everything fan related seems to be
working fine now.. Now I need to fix the temperature gauge, which
doesn't move at all.
Again, this is a '94 cutlass ciera V6 VIN M.
I found a few wiring diagrams on the Internet, but none of them had
anything to do with the temp gauge.
Cheap place to start is the coolant temp SENDER. Gauge and computer
have different parts for sensing coolant temp, you took care of the
computer with the sensor, now it's time to take care of the gauge with
Approximately 10/8/03 17:05, sempe uttered for posterity:
230 F is only slightly higher than the normal boiling point
at sea level. You could reach that temperature without boiling
by simply digging a deep enough hole in Death Valley, or just
use any available hot rock style geyser--which is how they
work in the first place.
It can also be reached by your grandma's pressure cooker.
Or that old steam engine.
Sorry it seems so high, but any physics websearch could
give you a pressure/boiling point curve. Boiling occurs
when the vapor pressure of the water is the same as the
external pressure on the water. With a roughly 30 lb
pressure cap, you get a boiling point of about 270 F if
I did the math right in my head.
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