Hi,
Here is an update on what I've done so far, but it hasn't been fixed yet.

Being the Engineer I am, I decided to trouble shoot this issue. From reading here in the web, I learned that this is supposed to be a 2-speed fan (Hi and Lo). Also, I looked at the relay box and learned that 2 relays are for the 'Hi' and one of these was the one the burnt. Also, none of the cables/wires are burned. Any ways, I have installed 2 good relays here and the fan still on. These relays are 'normally open' until 12v are applied. So when I check the car, as soon as I turn the key to the 'accessories' ON, I measure 12 volts at the inputs of the relays and so the fan is suppossed to be on because it closes/completes the circuit. This isn't normal as the car is cool because it was parked all night.

So, this tells that something is sending the signal to always turn the fan on. So, the first thing I supected and changed was the 'water temperature sensor'. This did not fix it. I went ahead and replaced the entire radiator fan assembly. This did not fix the problem. I spent about $300 for this so fa.

Now, I talked to my mechanic and we learned that the ECM is what controls the radiator fan, among other things like the AC and engine speed; on this 2000 Nissan Quest. So now he recommends replacing the ECM on this car and says that the part will be very expensive - about $700 bucks. He suggested I find a used one somewhere and he will replace it for me.

So here I go. I will hunt one of these down and see what happens...
Will update later.

Hi,
So, I finally had my 2000 Nissan Quest scanned by the Nissan Dealer in my area. They charge $135.00 just for scanning the computer (ECM) and reflashing it if it needs it. I told them about the issue I am having with my car and about the parts tha I have already replaced.

They didn't find anything with the scan and told me that the computer was not sending any codes. So, they looked at all the wiring that leads to the ECM and said that there was a 'short' somewhere. When they verified that all the wires were OK, they went ahead and removed the ECM. They opened the ECM and found two burn wires/contacts. They then told me that for sure the ECM needs to be replaced. They gave me a quote fro $1,500.77 just for the new ECM. I was very shocked.

So I told them 'No thanks' and asked them to put my car back together. The car is now back with me and it still has the radiator fan issue.

So, I did a search on the web and fournd a 'used parts' site where you can request any auto parts and they send your request all over to see if anyone is selling it. I got back 10 emails from several places that say they have my ECM. The cheapest is $150.00 to the most expensive of $499.00.

I opted to buy it from a place in Sacramento California for about $175.00 with a 6-month warranty. It is called sunrisenissan.net and they specialize in selling used nissan (and Kia) parts. Well, let's see how this turns out. I will post once I get the part replaced/installed.

Hi,
Just came back to inform everyone that my "Radiator Fan Issue" has been fixed.

From my previous post, I/we narrowed it down to the ECM. I received the part about 10 days ago and I finally had a chance to change it this weekend. The one thing that the 'salvage' place told me was that it might need to be reprogrammed. But that's fine. I was more worried about getting the correct part. This is why: The dealer will give you a part number which really is not the same part number on the ECM it self. Most places that sell these 'used' ECMs want the part number that's on the ECM to match it 100%. I didn't know what this number was except that it starts with: MECM-XXX-XXX. So that's why I felt I took a chance ordering the used ECM without knowing the part number.

Any ways, because I didn't know where exactly the ECM in the car was, I asked my mechanic about it. He told me it was under the dashboard, almost to the left of the front-passanger airbag. I told him I wanted to see the Original ECM in my car so that I can compare the part number with the used one.

When I got home, I took the glove box and some other 'pannels' off to see if I could see or access the ECM. I was able to see it, but could NOT see the numbers. So, I decided to remove it my self. Note, you must remove a metal bar that sits infront of it. It's not hard. Once you do that, there are only 2 screws holding the ECM to the car. Once you unscrew these 2 screws, you have to unscrew the one screw that holds the connector (and wires) to the ECM. Once the connector is out of the way, you have to 'wiggle' the ECM and pull it out at an angle (with its rear lifted up and its front pulled down).

Since I got it out, I compared the part numbers and most numbers matched. Only 4 numbers, which were at the end of the sequence, did not match. (I don't have those numbers with me but I have them in my car. I will post them when I get them). So I decided to try/install this used ECM to see, not only if it fixed my problem, but if my car would start. Once I screwed the connector on, I tried it by turning the 'accessories' ON. It worked. The Fan would not come on at all. I then turned the ignition/car ON and it did start fine. The engine ran good. So, I decided to leave the used ECM in and put everything else back together. I drove my car for a few miles and it ran fine. The radiator FAN problem was definitely fixed.

I then took a 150 mile trip and the car ran great. It is still running great. The radiator fan is working the way it should. It turns ON only when the water temperature rises.

I will comeback to let you know what the exact part number is for the ECM.

thanks,

BL

Hi,
Here is my final post for this issue. I am posting the part number for the ECM on a 2000 Nissan Quest GXE.

Original P/N:(Went bad -wires Radiator Fan 'ON' burnt inside ECM):

_______PPZ_________
_______YFCD________
MECM-C716 A1 9Z09

Used P/N(bought from Salvage place - now installed and works good):

______PPZ_________
______YFCD________
MECM-C716 A1 0609

Notice that the last 4 characters are different (9Z09 vs 0609). In my case, this didn't matter as my problem was fixed and my car is running good.

As far as PPZ and YFCD, I don't know what those mean/are, but they matched.

Good luck to all of you who have this problem. Let me know if I can be of any assistance here. I will post this on another website incase some other people have run into this issue.