Just noticed this morning, after my car barely starting, that my cooling fan must have stayed running last night. What can cause this to happen.. I have a 3 relay setup and if I pull the cooling fan relay #2 it will shut off, and when I put it back in it will stay off.. But, when I start the car again and shut it off, the cooling fan will keep running. I swapped the #1 and #2 relays already and it didn't make a difference... any suggestions?

btw-- it's a 97Z

 

Got any codes? If your SES is on, your fans will be too.

 

Actually, someone scanned my car before christmas and found this code: P0420 Three Way Catalyst (TWC) System Efficiency Below Threshold (Bank 1)

They told me that it mean one of the cats was bad. But, this cooling fan thing just started a few days ago. My battery would definitely have died by now if the fans were constantly running.

So, yes or no.. the fans will ALWAYS run when the SES light is on?? always.. like ignition off, after turning car off?

That means if the average person (who sometimes may get a SES light and not respond immediately would always get a dead battery.. unless they were driving an awful lot).

-- Also, can anyone clarify exactly what that code means?

-- Also the car is a 97, bought in 97, someone told me there is a 7 or 8 year federal emmisions warranty which is stated on the owners manual.. would this qualify as a covered repair at a dealer? -- if not, what would I have to do to fix it and get the SES light off for good?

thanks.

 

UPDATE -- I just found this on the web..

A: The computer in your vehicle uses an oxygen sensor in front of and behind each converter. The converter processes and reduces exhaust emissions. The computer program knows that there will be a difference in the information being reported from the front O2 sensor and the rear O2 sensor as the converter processes the exhaust emissions. As a converter ages it becomes less efficient. This loss of efficiency is known by the computer because of the information that the O2 sensors mounted before and after the converter report. Just because you have a converter efficiency code doesn’t always mean the converter needs to be replaced. A defective O2 sensor can cause this code to be set by the computer as well. Your technician has to check the O2 sensors to be sure that they are operating correctly and that other related systems are doing their job. If all checks good then a replacement converter is needed.

---

So, how do I test the oxygen sensors before and after the cat?? Can I use a multimeter?

And if they check out good, is there a way to just leave the "bad" cat on there and get the "right reading" sent back to the computer.. like with oxygen sensor sims or something?

Any help would be greatly appreciated.

 

The fans should not run with the ignition turned off..
They do run all the time when the ignition is on when the SES light is on, under certain conditions..
My thought is that #2 relay is sticking closed...
If #2 relay sticks closed it, will cause right fan to run on high all the time...
If, when you swap it for #1 relay, both of the fans run on low, it's sticking closed..
Possibly when you swapped the relays you didn't notice that subtle difference?
If above is true, get another #2 relay..
If however both fans are running [with #2 relay in it's #2 slot] on high, then you are somehow getting a 'ground trigger' to the relay in the 473 CKT from the PCM, which would not be normal with the ignition turned off..

 

So I went out and bought a new relay and put it in the #2 cooling fan relay slot. I reset my PCM and the SES light is off. I turn the car on and then off and the fan keeps running. I assume it is cooling fan #2 since when I pull the #2 relay it shuts off.. and when I put the relay back in, it stays off.. it will only come and stay on again if I start my car then shut it back off again.

Okay, so standing in front of the car looking down at the radiator what are the fan numbers from left to right?

I will really take a look at this tonight -- I mean, I will post the results of pulling various relays and swapping them.

Anybody else every have this problem??

 

The SES goes off when you turn the key OFF (you are also shutting down the computer), so no, the fans don't keep running.
I must have read your initial problem too fast. Sorry if I confused the issue.

Car components are viewed from the driving position or from inside, facing forward. You have a LH and a RH fan. For your year car, the fan relays do not correspond to one fan or the other, since both come on at the same time (low or high speed as conditions warrant).

So your fan are staying running and the SES is now off (or was it ever on)? Have there been any fan wiring modifications?

 

Correct, my SES light is off... i can get it to stay off for a little while by pulling the PCM fuse. It comes back on again after driving for a few mins... my sensor right before the cat is bad or the cat is actually bad.. that's a whole nother problem.

So, with the SES light off, when I turn my car off the fans keep running. I know when I pull the "Cooling Fan #2" relay they turn off. Then when I put the relay back in they stay off. Until I start the car again.

So there are Cooling Fan #1, #2, and #3 sensors in a 1997 Z28, but only 2 actual cooling fans?

No, I didn't modify anything. I will take a closer look at it when I get home in about an hour or so. I will post my findings.

Thanks for your help so far.

 

1,2 and 3 are relays and not directly tied to each fan (the early 2 relay fan setup was). The three relays are used to control fan operation and speed. You could have a ground on one of the relay control wires, leading to the relays. Locate the 10 way, flat connector on the RH shock tower and disconnect it (when fans are running with the key OFF). See if that kills the fans. In that connector, you will see a green wire in cavity "J" and a blue wire in cavity "H". Those are the two relay control wires from the PCM.
If you are into schematics, the bottom of this one is how it is wired.

 

I will try disconnecting the connector at the shock tower tonight.

Another question: If I take one of the relays and put it in the FOG LAMP slot, and the fog lamps work fine... does that mean the relay is 100% A-OK? Is there a better test?

 

Okay -- I finally got around to looking at this again. Here is the deal. I shut the car off and the fans keep running.

If I pull the clip at the shock tower, they turn off and stay off when the clip is plugged back in.

Here is some more troubleshooting... I turn the car off, the fans are still running... so I

Pull cooling fan relay #2, it still keeps running... so I put it back in.
I pull cooling fan relay #3, the fan shuts off then turns right back on when #3 is reinserted.
So, finally.. with both back in, the fans still running, I pull cooling fan relay #1, the fans kick off, I put the relay back in and the fans stay off.

I bought a brand new relay and tried it in the #1, 2 and 3 position with no difference... what is my next step?

 

Get the codes pulled again, and see if there are any new ones. Autozone can pull the codes on your car.

 

Sounds like you might have a marginal ground on the dark green wire that operated relay #1, causing the relay to be held operated. Do you have a meter or test light and the knowledge to chase a grounded wire? Could be just a the wire is chafed and touching to metal on the car.

 

Yes I have a multimeter... How do I use it to find out if the dark green wire is grounded? I will have a few hours to work on this tonight so any help would be great!

 

It will help if you can read the schematic. Unplug C100 on the RH shock tower and remove relay #1. Set your meter to OHMs and connect one lead to ground. Connect the other lead to the drk green wire to see if you get a reading. That will test that secion of wire. You can also look back toward the PCM on the drk green wire to see if it is grounded that direction. It should only have a ground on it when the fans are supposed to be on. Make sure you have a high impedance meter (at least 10 megohm), so you don't damage your PCM.