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Engine Code P0691 Fan 1 Control Circuit Low

8K views 10 replies 4 participants last post by  jworks 
#1 · (Edited)
Needing some help with this.

*Series of events*
-I heard a weird noise from my engine bay, I shut off my car and popped my hood. I saw my serpentine belt we becoming unbanded and ready to snap any moment. I started the car to see if I could get home, then it snapped in the Costco parking lot.
-I replaced both belts. (I was already under the car, so I did both)
problems always come in pairs...
-couple days later my car is over-heating badly coolant temp reached 250º
-did some trouble shooting and research, I ended up replacing the Fan Control Module -Link : https://www.amazon.com/Gates-Racing...t=&hvlocphy=9031008&hvtargid=pla-688878117277

Everything works great and my car is cooling it self back to 199º perfectly
-after driving on the freshly installed FCM, the engine code come up (P0691).
-I have had it erased twice by Autozone, only to return again. I've checked the 60amp fuse (slot 1). the fuse is fine, I even tried a new fuse to see if that would work.

I have run out of ideas for what could fix this. I've looked on the forum and tried squeezing my large coolant line and plugging my overflow to put a vaccuum on the line and get the air bubbles out. Nothing has worked thus far. I'm hoping someone can help me out. Any help would be greatly appreciated.

Car: 2009 Saturn Sky Redline
Miles: 79,000
Transmission: Automatic
 
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#2 ·
It is always something.. happens in a Costco parking lot. Never fails to spoil the Permagrin.

Replacing the belts is a good thing, at 79,000 miles. 250 degrees is not so good.
Replacing the fan control module sometime fixes the problem, as you said, your car is cooling itself back to 199 degrees.

The reoccurring error code... ( P0691 ) and having it erased by Autozone is the problem, fuses seem ok for now.
IS.. your car still overheating? ARE.. your temps still at 199?

IF your temps are still good at 199 while driving, no signs of high temps, no puddle of fluid under your car, no loss of fluid in
the expansion tank, it sounds like it is an electrical problem only, not mechanical, does not prevent you from safely driving the car.
Again here are the temps rising above normal range? High temps can damage motor parts.... and a trip to the dealerships.
DO you hear the fan run while sitting still? Does it run on,.. after you shut down?

Reset battery ECM/BCM, disconnect for 10 + plus minutes, then see if it resets itself, does the code return?

Old fluid... has it been replaced at this point @79k? Stuck thermostat if your still seeing high temps? If your not... seeing high temps
then our guys are going to have to determine what else might be wrong for you here? With high temps... it could be.. the WP?
Has it been changed during your ownership? Previous history of the car, was it changed out before you owned it?

One of our electrical gurus will be around shortly... to help you.

LAC
 
#3 · (Edited)
Does the fan ever come on? How did you determine that the FCM was bad?

P0691 is defined as "Low voltage" but it doesn't mean what you probably think it does. At least it is not what I initially thought it was.

The fan is supplied with battery voltage (B+) and the control is at the ground side through the FCM.
This means that there should be B+ at the FCM when the fan is not running, and that voltage will decrease as the fan speed is increased.
With the fan at its maximum speed (90-94%) the voltage at the FCM should be nearly zero.
The correct value of the voltage at the FCM is calculated for different fan speeds, and P0691 is activated if the voltage is ever lower than expected.

Because this started right after a belt casualty I would look for physical damage to a wire, connector, or to the fan itself.
 
#4 ·
LAC SKY/ JohnWR - First, thanks for the taking the time to read and respond. in order:

occasionally, it will heat to 217º-222º but then immediately the fan kicks on a shoot down to 199º. I would say 85% of the time, it's consistently 199º-201º

no puddles or fluids under the car at the moment. The expansion tank is at operating level. I do hear the fan running while I drive the car. It does run when I turn off the car and pump gas.

I have not tried resetting the battery. I can do that tonight. I have the GMPP stage 2 on my car, so I always hate disconnecting the battery then the CPU has to re-learn the tables for my stage 2. (takes about 500 miles for a full re-learn)

I am a former GM employee. I bought the car brand new. It is the original coolant fluid. My initial thought of the failure was some kind of physical damage cause by the unbanding of the belt turning and hitting a wire. But...I inspected it well down there and could not any evidence of damage.

I determined it was the FCM but deduction. I learned the FCM is a relay by reading on the forum and websites. Relays tell the fan to turn off and on. When I determined there are no Relays in the fuse box for the 2.0L, the only other RELAY option was the FCM, so I replaced it because it was plug and play.
 
#5 ·
LAC SKY/ JohnWR - First, thanks for the taking the time to read and respond. in order:

occasionally, it will heat to 217º-222º but then immediately the fan kicks on a shoot down to 199º. I would say 85% of the time, it's consistently 199º-201º

no puddles or fluids under the car at the moment. The expansion tank is at operating level. I do hear the fan running while I drive the car. It does run when I turn off the car and pump gas.
This sounds perfectly normal to me.
I have not tried resetting the battery. I can do that tonight. I have the GMPP stage 2 on my car, so I always hate disconnecting the battery then the CPU has to re-learn the tables for my stage 2. (takes about 500 miles for a full re-learn)

I am a former GM employee. I bought the car brand new. It is the original coolant fluid. My initial thought of the failure was some kind of physical damage cause by the unbanding of the belt turning and hitting a wire. But...I inspected it well down there and could not any evidence of damage.
I do not see any need to "reset" the ECM. That doesn't mean that it won't help, but this code is not learned, as far as I can tell, so resetting it as you have done is all that should be necessary.
I determined it was the FCM but deduction. I learned the FCM is a relay by reading on the forum and websites. Relays tell the fan to turn off and on. When I determined there are no Relays in the fuse box for the 2.0L, the only other RELAY option was the FCM, so I replaced it because it was plug and play.
Technically speaking the FCM is not a relay, it is a variable speed controller. Relays turn on and off, a speed controller modulates. The 2.4 has a relay module that provides high/low/off fan speeds, but the FCM gives the 2.0 infinitely variable fan speed.

This code is purely electrical, so as long as the car is operating at normal temperatures there is no reason to worry about coolant, bubbles, thermostat, water pump, etc. When you have it reset does it come back before the fan comes on, or while it is running?

Possible causes of this code are the ECM, the FCM, the fan, and the wiring or connectors. Because it happened only after the belt broke up I am still suspecting some physical damage to something. Check all of the connectors by unplugging them and plugging them back in, and look at anything that could have been hit by belt debris.
 
#6 ·
JohnWR-
Sounds like we are on the same page. I suspect physical damage as well, even though I can't for the life of me, see any shred of evidence that resembles damage. I will go under with a flashlight tonight and check all the connections. Beyond a loose connection, I am stumped. Thank you for taking the time to help me troubleshoot.
 
#7 ·
I would've expected a wiring problem first, but if you have eliminated that, then I would look at a (maybe partially) failed, or incompatible, controller module - despite it being new.

Are you sure the FCM was actually a problem? Did your fan stop running? If not, I would try swapping back. If so, maybe try a new controller.
 
#8 · (Edited)
TomatoSoup- It's funny you brought that up, I actually am questioning if the FCM I purchased could be the culprit. The website "Gates" says it is compatible, but I do know the light came on after I installed that FCM (as did my cooling fans as well- no issues on that front). Everything else works though, the fan is spinning, my car is at 199º. P0691 will not go away. Does anyone know what the original brand FCM in the vehicle is? Possibly ACdelco?

The Gates FCM:
https://www.amazon.com/Gates-Racing-...a-688878117277

Tonight I will plug in my old FCM and see if the service engine soon light goes off (even though my fans wont run). This will tell me if it's a gates issue.

The Gates website confirms the correct part number FCM106:
https://www.gates.com/us/en/ymm/sea...009&make=Saturn&model=Sky&engine=4-Cyl.+2.0+L

I'm not sure where to get an OEM FCM. there does not seem to be any indication of brand type on the existing.

Thank you for reaching out in trying to solve this matter.
 
#9 ·
I'm not sure where to get an OEM FCM. there does not seem to be any indication of brand type on the existing.
I know that others have used cheap (~$20) Ford Crown Vic controllers off ebay and haven't had an issue - except one reporting an early failure of the replacement. Not sure who the OEM maker was, though.
 
#11 ·
*UPDATE* 6.20.19

Installed the Crown Vic FCM Controller $20 on amazon prime- code turned off and fan is working. Drove it last night and today, no issues (knock on wood)

Thanks for all the help guys.

some food for thought....do not go to FORD to buy it (quoted me $193 ea) it's $19.59 on amazon .

Thank you
 
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