Fans always running

My radiator fans are always running and the engine temp. gauge never moves up... After turning the engine off the fans continue running for a couple of minutes and then shut off... I'm thinking the coolant temp. sensor has gone bad??

I got a P0128 code from my code reader...

with the P0128 code some people are claiming that replacing the thermostat has fixed the issue. I have not had any personal experience with this code though. Fans should run anytime the AC is on.

And now the car won't start... An old problem... It fires, starts, stumbles and dies... This morning it ran perfect...

I replaced the ECT and thermostat... Car started and ran... But the fans start running right away and stay running after turning the car off... The temp gauge still never gets off the bottom... And I still read a P0128 code from my code reader... I buzzed the short length of harness from the ECT to the connector on top of the LIM.. It buzzed good... What now??

Have you tried resetting the computer since changing the thermostat? My wifes car had the same symptoms last winter as you described. I would disconnect the battery overnight, although an hour is probably long enough, then everything would be fine for a couple of weeks before it would act up again. Eventually, the weather got warmer and the problem went away. I replaced the thermostat and flushed the cooling system over the summer. This winter, I have not seen the problem reoccur at all. In my case, the thermostat seemed to be the long term fix. Good luck!!

Have you tried resetting the computer since changing the thermostat? My wifes car had the same symptoms last winter as you described. I would disconnect the battery overnight, although an hour is probably long enough, then everything would be fine for a couple of weeks before it would act up again. Eventually, the weather got warmer and the problem went away. I replaced the thermostat and flushed the cooling system over the summer. This winter, I have not seen the problem reoccur at all. In my case, the thermostat seemed to be the long term fix. Good luck!!

No, I have not tried resetting the computer... I will try that tomorrow morning... Thanks...

Any other thoughts or ideas from anyone are appreciated...

OK, problem seems to be fixed... I first tried to clear the DTC by disconnecting the battery for about 90 minutes... That did not clear the code... So I used my Actron DTC scanner to clear the code... Once I did that everything is working properly now... I just don't know why disconnecting the battery for 90 minutes did not clear the code but the erase function on the scan tool did...

Ahhh...the old Temp Gauge issue. Well, we have a 2001 Impala V6 with the 3.4 - 3400 engine. At 50k miles we got the low coolant warning light. Yet the system was full. I looked at the radiator cap to find the sludge of dex cool death. So I read the blogs and it leads to getting a new cap - Stant model. This works for a while. Then the fans stay on after the car shuts off and the temp gauge doesn't budge causing check engine light to come on. After scanning with OBDII, I get the ol 0128 code - Temp not up to spec. No crap...I could tell that with the gauge not coming up at all. This happend last December (2005). So....take it to a dealer and they scan (for $65) and it says its a coolant sensor. When changing the sensor, they claim to see a coolant leak in the upper intake. Any of this sound familiar? I had to laugh when I found this site. So dealer wants $700 to $800 to replace this (hell, to put in the $25 sensor it was $125). I get the gasket fixed (not at the dealer - but would love to know if GM still covers this after 36000 and 3 years, as I saw someone said they would for a one time fix). So after the coolant sensor, gasket, radiator cap...all was fine. That is...until it cold again this year. Same thing happened this winter. Fans staying on, gauge not budging, this time...at least no leak in the gasket. Go back to the dealer, of course its past their 12kmile 12 month warranty and simply ask for the sensor. Its now $29, but the doofus I talk to now says, change the thermostat, not the sensor. So I buy the thermostat and sensor.

So far so good. After changing the thermostat and since I was in there, changed the sensor as well, and the gauge actually got above 160 degrees and is in the middle of the gauge now.

Forgot to mention that its a cold weather issue. Gauge would come up fine when ambient temp was greater than 30 or 40, but when it got lower, temp gauge stopped working, fans came on, even after car engine was shut off...which all leads to thermostat. Here's why - if the thermostat is faulty, it won't allow circulation past the coolant/temp sensor an inch away. The temp sensor can burn out if fluid is not going past it. This sensor, when it gets hot, tells the computer its too hot - so kick the fans on. Even though engines not overheating or even hot, the sensor doesn't know this since its flow is restricted. So...this should answer why the fans come on... as well as the check engine light - P0128 should be the code.

Adios!

Disconnecting the battery doesn't always clear the codes on OBD-II cars. Normally, they will require the use of a scan tool to do so. The PCM will not recogize the new parts until the codes are cleared, so that is why the car continued to act up.

OK, here it goes again.. After 1 day of the temp gauge working correctly and the fans turning on when only they should it's messed up again today... The fans again are constantly running and the temp gauge is stuck on the bottom... And the P0128 code has come back... This is after installing a new ECT sensor and a new 180 degree t'stat a few months ago...I erased the code and the fans are off again for now... What the heck is going on???

you may have a grounded/shorted wire harness between the ECT and the PCM.

you may have a grounded/shorted wire harness between the ECT and the PCM.

Thanks, I'll check for a short... I'm also going to put in a new t'stat on the off-chance that the one currently installed is defective and stuck open, or partially open...

Gems - I've been through this too, and for my 01 Impala LS, the fix was putting in the best quality 195 thermo I could get (I believe it was a Gates), and also replacing the temp sensor (I'm not sure what an ECT is - is that the temp sensor?) Previously, I had this problem and only had been replacing the sensor, but the fan running and temp gage dropping to 0 would come back. Pulled the PCM fuse to reset, and the problem has been gone since it was done in Nov 2006.

Gems - I've been through this too, and for my 01 Impala LS, the fix was putting in the best quality 195 thermo I could get (I believe it was a Gates), and also replacing the temp sensor (I'm not sure what an ECT is - is that the temp sensor?) Previously, I had this problem and only had been replacing the sensor, but the fan running and temp gage dropping to 0 would come back. Pulled the PCM fuse to reset, and the problem has been gone since it was done in Nov 2006.

Yup... I kind of have 2 threads going here on the same topic... Read my "Stuck Open Thermostat" thread here... I think I have the problem resolved, just like you have described... (2001 LS here also)

Hello, new to the forum here. Glad to see my Impala is not the only one doing this. It has been a cold weather issue for me. It has done this for about 2 years, but in the summer it goes away.
Now here is my question. My passanger side cooling fan motor seems to going bad (ratteling and making a horrible squealing sound). What I found interesting is I unplugged this one fan tonight, suddenly the fan on the other side stopped running after the car was shut off.
I know this is a temp fix, but is a good enough temp fix? Must you have both fans running?
Thanks

The two fans are probably needed for summer driving when it starts to get hot. Not only do they keep the engine operating temp in range at low speeds or idle, but they also cool the A/C condensor for better A/C performance. To do a permanent fix, would suggest replacing the temp sensor and the thermostat with a high quality Gates 195 degree (assuming your cooling system is in good shape, otherwise go for the 180). Also pull the PCM fuse to reset the system, and the excessive fan running issue should be gone. Also suggest replacing the fan or fans based on how bad they are. Search elsewhere in this forum - someone posted that they found a source for replacement fans at a reasonable price.

The car ran fine today, so until I can get it in the shop, it will do. It is just interesting the one fan is running, but does shut off with the car now, and the temp gauge is still not working.
Thanks for your help. I am having a lot of the issues that are talked about on this forum, with the Impala and it is just nice to have some feed back on them.

If you read my other posting here on a related topic (Stuck open thermostat) my problem seems to be solved after replacement of both the ECT sensor and thermostat... I was advised to get a good quality thermostat like AC Delco OEM... As a backup I have a GATES 180 degree t'stat on order...

weak alternator.

go to auto zone and get your alternator checked while still on the vehicle.

it will show how many amps the alternator is pushing out.

mine is only pushing out 32 amps. it should be pushing out 105 amps.

replace the alternator and the problems with the gauge and the a/c cooling should go away.

weak alternator.

go to auto zone and get your alternator checked while still on the vehicle.

it will show how many amps the alternator is pushing out.

mine is only pushing out 32 amps. it should be pushing out 105 amps.

replace the alternator and the problems with the gauge and the a/c cooling should go away.

Huh????? My original post on this problem was over 1 year ago... Problem fixed at that time by replacing a stuck open thermostat and a bad ECT sensor... Cleared the codes and everything has worked perfect for over 1 year now... Clearly not an alternator problem...

weak alternator.

go to auto zone and get your alternator checked while still on the vehicle.

it will show how many amps the alternator is pushing out.

mine is only pushing out 32 amps. it should be pushing out 105 amps.

replace the alternator and the problems with the gauge and the a/c cooling should go away.


I find your comments very wrong....all wrong....and this posting is too old and should be locked......alternator output is dependent on load not rating.......so vehicle type and operation of devices/battery condition will determine alternator output..... but a 105amp alternator will not put out 105amps, but a lower value....if you had a dead good battery the most would be 90amps.......out of alt. to charge it with all power equiptment on..

My radiator fans are always running and the engine temp. gauge never moves up... After turning the engine off the fans continue running for a couple of minutes and then shut off... I'm thinking the coolant temp. sensor has gone bad??



I just fixed this problem in my impala try disconnecting the negative terminal for a couple hours to reset the computer. Then reconnect it after that it should be all good

I guess people don't look at the date of the original posting... I had this problem over 1 year ago and I resolved the problem over 1 year ago... Please read thru all the replies in this thread...

This thread should be locked....