Ok to start here is what im working with
2000 Z Auto tuned with HP tuners to have the Fan kick on after car is turned off to help cool, dont know if this is relevant but i thiought i would share.
Noticed the other day while puttering around in some heavy traffic my engine was extremely hot the temp gauge was past 3/4 almost to full hot
When i got home i noticed my cooling fan wasnt coming on, so i swapped out relays and also the fuse to see if that fixed it, nothing
Also we jumped the relay but im not sure we jumped the proper posts on that so some insight on that would help
Swapped in a brand new fan motor even though the other one still worked but was making a small squeal indicating it wasnt long before dead
We started my car and turned on the AC which should engage the Cooling fan and nothing, did the same thing on my buddies car and the fan kicked on right away
We traced the ground G112 and found those were good, also we used a test light at the ground for the plug at the Fan motor plug and found that the ground is fine
So we traced it to be a power problem and thinking that the PCM isnt telling the Fan to switch on ( How can i test this? )
or
The wiring supplying power to the Fan motor isnt working ( How can i fix this? )
Could it be the ECT not communicating with the PCM? ( Testable? )
Any and all help is greatly greatly appreciated as im stuck and very frustrated. Also i have the GM shop manuals but its not helping that much at the moment
Thanks very much
Edited 1 time(s). Last edited Friday, June 15, 2007 11:40 PM
Would anyone have any info at all?
Im really stuck
I know nothing of the HP Tuners modification---so the following may be no help at all---but this is how I see it for the OEM installation.
Here is a link to the 12volt.com's good article on automotive relays.
http://www.the12volt.com/relays/relays.asp
Power is usually fed to pin 30
When the relay is energised this is fed out of the relay on pin 87
Pins 85 and 86 are connected to each end of the operating coil,and, in a basic layout it would not matter which way they were connected. In some installations a diode(One way valve) is wired across pins 85 and 86 and then the operating coil must be connected observing polarity.
Using Kardain's Cooling Fan diagram from:-
http://www.projectwyldfyre.com/
This shows a 30 amp fuse (Hot at all times) supplying +12 volts to Pins 30 and 85 of the relay base
30 will be fed to 87 when the relay is energised, on to the cooling fan and grounded at Ground point G112
If you removed the relay from the base(connector) and jumpered pins 30 and 87 the fan should run. The correct way to do this would be to have a 30 amp fuse in the jumper wire.
If this works Ok the energising circuit is suspect, check for +12 volts at pin 85---if OK ground pin 86(This is what the PCM does to bring on the fan) and the Fan should run.If the Fan then operates the problem is down to the PCM NOT providing the Ground when it should.
[Could it be the ECT not communicating with the PCM? ( Testable? )]--- Yes,but see how you go with the above, first.
Good Luck
Alont
Thank you very much i will test this today
alont wrote:I know nothing of the HP Tuners modification---so the following may be no help at all---but this is how I see it for the OEM installation.
Here is a link to the 12volt.com's good article on automotive relays.
http://www.the12volt.com/relays/relays.asp
Power is usually fed to pin 30
When the relay is energised this is fed out of the relay on pin 87
Pins 85 and 86 are connected to each end of the operating coil,and, in a basic layout it would not matter which way they were connected. In some installations a diode(One way valve) is wired across pins 85 and 86 and then the operating coil must be connected observing polarity.
Using Kardain's Cooling Fan diagram from:-
http://www.projectwyldfyre.com/
This shows a 30 amp fuse (Hot at all times) supplying +12 volts to Pins 30 and 85 of the relay base
30 will be fed to 87 when the relay is energised, on to the cooling fan and grounded at Ground point G112
If you removed the relay from the base(connector) and jumpered pins 30 and 87 the fan should run. The correct way to do this would be to have a 30 amp fuse in the jumper wire.
If this works Ok the energising circuit is suspect, check for +12 volts at pin 85---if OK ground pin 86(This is what the PCM does to bring on the fan) and the Fan should run.If the Fan then operates the problem is down to the PCM NOT providing the Ground when it should.
[Could it be the ECT not communicating with the PCM? ( Testable? )]--- Yes,but see how you go with the above, first.
Good Luck
Alont
Alont,
I've tested the relay like you said, and everything worked as you mentioned. What is the PCM and How do I fix it or is it something that can be replaced. What is the ECT? Thanks alot. ALso for now would it hurt anything if I left 86 grounded so that it made the fan always run, until I get a fix for the problem!
The PCM is the Powertrain Control Module, really just the latest name for the computer, it can nowcontrol transmision shift points etc.
The ECT is the Engine Coolant Temperature Sensor, it monitors the temperature of the coolant and, by sending this info to the PCM, grounds 86 to bring on the fan when required.
It will be OK to leave 86 grounded as you have,until you get it fixed---you are only doing what the PCM would--except all the time!
If the ECT is defective this would be the cheapest thing to replace--the PCM would be more expensive and may/will need posibly a dealer programming. Perhaps someone on the forum will advise
Alont
Ok , I tried my Theory in how to test the ECT. I jumped the plug that connects into the ECT. This didnt turn on my fan like i wanted it too. So I went too find some schematics. In the picture below it looks as though the ECT acts as a POT, controlling how voltage is being sent to the PCM. Well that would mean that a jumper wire would put the least resistance on it, causing it to send max voltage to the PCM right? Nothing seemed to happen. Does anyone have any idea of how to test the ECT? I just bought a brand new one that didnt do change my out come. what would Be Next to check?
Has anyone even thought about trying to replace the relay, and see if that does the trick
. Relays, do go out ya know.
OK I'm stupid never mind, you already did that. My brain must have skipped over that part when I read it. Maybee there's a problem with the wiring somewhere or something.
That is what I'm thinking also. I'm going to uncover the location of where the PCM is and see if there is anything out of the ordinary. I did notice that there is this sensor or looks like a sensor in the passenger fenderwhell, where the PCM is located. It is attached almost right behind the right head light on the inside of the fender. Really close to where the right side turn signal is located on a 98 Pontiac Sunfire. I see a plug that looks like it is missing some wires... I'll try an post some pics of it later today. Does anyone know what it is?
In my '93 3.1 info +5 volts is applied to the YELLOW ECT Sensor input(through a resistor) and the BROWN wire is grounded, within the ECM (PCM in yours)
The ECT is actually a THERMISTOR, this resistance drops as the temperature INCREASES (i.e. it is the REVERSE of a normal resistor)
My tables show 241 ohms at 90 deg C and 9,240 ohms at ZERO deg C, at normal engine temperature the PCM?ECM will see 1.5 to 2.0 volts
[Well that would mean that a jumper wire would put the least resistance on it, causing it to send max voltage to the PCM right?]
--Correct, minimum resistance in the ECT--it's now a dead short---maximum current through the PCM resistor---maximum voltage developed across the PCM internal resistor---Just check your PCM DOES have an internal resistor and still works this way!
Please be wary of shorting anything to do with the PCM, in case you damage it!!
-------------------------------------------
Disconnect the wiring connector at the Coolant temperature sensor--now measure the voltage across the YELLOW and BROWN pins in the disconnected wiring---if it works as mine it should be between 0 and 5 volts----what is it?
Can you note the air temperature and then check the resistance reading of the sensor?
At normal engine temperature the PCM/ECM will "see" 1.5 to 2.0 volts
-----------------------------------------------
You will have tables of resistance, related to temperature, in your shop manual, also there will be a chart or procedure to follow to check the Coolant Temperature Sensor itself. See if you can find that info in the manual.
I only have info for a 1993 model, any other info I get from the forums or web.
Alont
I've got a 2.4 sunfire so mine is a little different, but that looks alot like one of the plugs going to the A/C compressure to me. (pic is hard to tell exactly where it is). I thought our ECU's (PCM) where located behind the glove box?
