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95 Pontiac Transport 3.1L
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rsuda
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May 27, 2006, 3:43 PM
Post #1 of 9
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95 Pontiac Transport 3.1L
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I'm having trouble with my radiator fan(only have one) kicking on.The only time it runs is when the A/C is on.I thought it might be a sensor so I changed both(temp.sensor & sending unit)with no success.Any ideas,THANKS!!!!
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DanD
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May 28, 2006, 1:39 PM
Post #2 of 9
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Re: 95 Pontiac Transport 3.1L
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I’ll have a look tomorrow at a wiring diagram and see if I can come up with any ideas.
Bump this back up to the top if I forget.
Dan.
Canadian "EH"
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DanD
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May 29, 2006, 6:02 PM
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Re: 95 Pontiac Transport 3.1L
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Are you still looking for help????
Canadian "EH"
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rsuda
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May 29, 2006, 8:06 PM
Post #4 of 9
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Re: 95 Pontiac Transport 3.1L
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Yes,Please.Anything would be helpful.THANKS!!!!!!
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DanD
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May 30, 2006, 4:38 AM
Post #5 of 9
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Re: 95 Pontiac Transport 3.1L
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With you saying that the fan will come on with the AC; we know that the fan motor, relay, fuses are ok and the ECM (computer) is capable of turning on the fan.
You’ve all ready replaced the sensor so it should be ok; all that’s left is the wiring, connections or the ECM itself not interpreting the ECT (engine coolant temperature) sensor input properly.
Is there a check engine light on; if so what is the code?
The way it is suppose to work is that when engine temp reaches 212 degree the ECT input to the ECM should trigger the ECM to apply ground to the cooling fan relay’s pull-in coil. Closing the contacts in the relay, turning on the fan. Once the temp is 198 or below the ECM removes the ground, which opens the contacts of the relay turning off the fan.
What we need to know is the signal from the ECT getting to the ECM and at the proper value.
A scan tool is the easiest way to see the ECM’s interpretation of the ECT signal but with an ohmmeter you can test whether the signal is getting to the ECM.
You’ll have to drop down the ECM to get at the connectors that’s to be able to back probe the ECT connection.
Back probing is a way of testing a circuit without unhooking the connector and at the same time not damaging the wire insulation. You can use a small diameter piece of wire like a paper clip, that you should be able to slide into the back of the wire connector alone side the electrical wire; until you feel it make connection with the terminal inside the connector.
You’ll find the ECT signal wire (Yellow) in connector position C10 you may have to disconnect the ECM to see the numbering on the side of the connector. You should also find a purple and Lt green wire on either side of the yellow.
Next look for the sensor ground (black) in position D2 there should be a tan/white on one side and an empty spot on the other.
These two wires may not be in the same connector.
Once you find these two wires, install the back probes, reconnect the ECM and then connect your ohmmeter to the probes.
The engine should be cold when you take your first reading that so you can compare the resistance value of the sensor and wiring to ambient temperature. After that start the engine, the resistance value should start to go down as the engine warms.
Here’s a chart that gives you resistance values for different temperatures they are not exact but should be close, within 30 to 40 ohms.
If the readings are incorrect and you’ve confirmed that the sensor itself is sending the proper values; start looking for a connection or corrosion problem in the harness.
If the readings look ok according to the chart you may have a bad ECM.
Dan.
Canadian "EH"
(This post was edited by DanD on May 30, 2006, 5:00 PM)
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rsuda
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May 30, 2006, 6:05 PM
Post #6 of 9
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Re: 95 Pontiac Transport 3.1L
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Dan,Thanks for the info.I'm getting a #34 trouble code(Vacuum sensor-MAP sensor)which I think is another issue.Any ideas on this one? THANKS!!!!!
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DanD
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May 31, 2006, 6:55 AM
Post #7 of 9
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Re: 95 Pontiac Transport 3.1L
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You’re probably right that the MAP code doesn’t have anything to do with the cooling fan.
Unless the ECM is causing the fan issue which in turn could also be the reason for the MAP code?
Testing a MAP circuit can be a little drawn out without having a scan tool to read sensor data. You’ll have to know what circuit is reference voltage; signal return and what pins of the ECM you need to back probe.
It’s just too difficult for me to try and remember all of the steps, in the proper sequence to tell you how to test this. I would have to quote a service manual word for word; again just to time consuming. Sorry.
Maybe it’s time to take the van in and have it diagnosed?
Tell us what they find and maybe we’ll be able to confirm this for you.
Dan.
Canadian "EH"
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rsuda
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Jun 3, 2006, 12:17 PM
Post #8 of 9
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Re: 95 Pontiac Transport 3.1L
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Hey Dan,Since the vans not acting up,no need to take it in yet,it will only be a guessing game.Getting back to my radiator fan problem.On the ECM,there's a tab called a PROM that connects to it.I was wondering how do I know if my ECM is bad or the PROM or both? THANKS!!!!!!
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DanD
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Jun 3, 2006, 9:08 PM
Post #9 of 9
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Re: 95 Pontiac Transport 3.1L
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My answer to the prom question isn’t going to sound to professional but you throw the dice and you take your chances. It kind of goes right with the question; what came first the chicken or the egg?
Maybe someone else here has a better answer but from what I’ve experienced is that when a prom goes bad the ECM will code it. The prom is what tailors the ECM to your vehicle options; ie. engine, tire size, trans ect. The only time I’ve changed proms is when the ECM has coded it as a fault or when a service bulletin has brought an up-date in its programming to my attention.
Dan.
Canadian "EH"
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