Cooling fans won’t turn off/Temp gauge spikes/engine won’t fire up??? Help

[nvrgnadi]

I have a 2005 subaru legacy Limited 

Car ran fine….

Parked for a few months while I replaced and refurbished a bunch of bushings and repainted a bunch of underside parts etc…

I did minimal work under the hood so to my surprise

PROBLEM

when I tried to restart the vehicle it would turn over but not fire up.  
 

The cooling fans kick on when the key is turned to the “on” position and they both run non stop continuously until I turn the key off.  
 

The temp gauge also jumps right to “hot” as soon as the key is turned to the“on” position. 
 

There are a few codes that are showing 

Coolant temp sensor 

 

 

[silverton]

Sounds like the coolant temp sensor and/or its wiring went bad. 

[Max Capacity]

Sitting for a while, I wonder if mice eat something ? FWIW, I keep Tom Cat mouse blocks placed around and in the car.

 

https://www.google.com/search?gs_ssp=eJzj4tVP1zc0LDcxNkhJNi4wYPQSLsnPTU4sUcjNLy1OVcjOzMlJLQIAxTcLuQ&q=tomcat+mouse+killer&rlz=1C1OKWM_enUS906US906&oq=Tom+Cat+mouse&gs_lcrp=EgZjaHJvbWUqDAgCEC4YChiABBjlBDIJCAAQRRg5GIAEMgkIARAAGAoYgAQyDAgCEC4YChiABBjlBDIMCAMQLhgKGIAEGOUEMgkIBBAAGAoYgAQyCQgFEAAYChiABDIJCAYQABgKGIAEMgwIBxAuGAoYgAQY5QQyCQgIEAAYChiABDIJCAkQABgKGIAE0gEKMTEzMDZqMWoxNagCDLACAQ&sourceid=chrome&ie=UTF-8

[Max Capacity]

You did verify the green connectors are not plugged together behind the passenger carpet ? 

[nvrgnadi]

They are not connected - Can confirm

I looked into the problem and apparently there was a recall on a relay that if left unchecked could cause a power spike and fry something in the cooling fan circuit inside the ecm.... my luck it waited 20 yrs before doing so.  

 

The recall expired in 2017 (learned that was a thing).  

 

So my next move assuming that is the issue and the ecu is toasty.

I either source another ecu for the car or I repair the one I have. 

Being I have a protune on the car I think i'll opt to have the current one repaired or atlesast send it out to a repair shop that could look into it.  

I'm going to go through all the troubleshooting checks on my end again to make sure I didnt miss something but the fans not shutting off for any reason is a pretty clear indicator of the ecu being compromised.

1st question  - I have a accessport that Ive never used on this car yet.  It's brand new.  Can I save the protune thats on the vehicle now onto the accessport?  

Incase i have to swap out ECU's id prefer to not just lose my $600 pro-tune map that I've had for years.

2nd question  - Does anyone know of any Subaru ECU repair shops that they'd recommend?

I'm sure there are many out there I've just never dealt with any of them.

Thanks for all the help so far.

 

Edited November 29 by nvrgnadi

[KZJonny]

1 hour ago, nvrgnadi said:

1st question  - I have a accessport that Ive never used on this car yet.  It's brand new.  Can I save the protune thats on the vehicle now onto the accessport?  

Incase i have to swap out ECU's id prefer to not just lose my $600 pro-tune map that I've had for years.

I am pretty sure the answer is no. For the AP to 'talk' to your ECU, the first thing you do with it is to apply the COBB AP framework. So, you flash the ECU with COBB firmware. Someone else may be able to confirm or deny, but I think this will write over any map already flashed with the COBB Stg 0, essentially.

I am pretty sure you can use ROMRaider to pull a copy of your current map off the ECU however, give you a backup for if the ECU does fail and needs replacement. Fingers crossed it can be repaired.

If you start looking for an ECU and would like to avoid the hassle of reprogramming, try to find a car of the same year and transmission as yours being parted out. Get the ECU, BIU (Body Integrated Unit), lock cylinder and keys all at the same time ideally. They are coded alike and either have to move together, or you need to get the new ones reprogrammed to your car. These days, it is probably easier to just buy scrapyard stuff than pay for that service. (I am not 100% sure '05 keys had immobilizer chips in them, but maybe? I should know, I have 2 x 05s, but I've also driven the car for weeks on the valet key... which makes me think that it may be another '05 oddity that makes them different from all other years.)

[Infosecdad]

05 GTs have the immobilizer chip. 

[tysparks81]

Before you dive into this thinking it is your ECU, check your ignition fuses under the dash.  I suspect that you have a fuse blown that is keeping it from starting.    More than likely you have a short with the Fan switch/Fan relay or one of your coilpack wires like me.  Identify and fix the short first!  Then replace the IGN fuse under the drivers side kick panel.  I was having the exact same symptoms as you describe with a CEL for the SI drive(your 05 doesn't have the SI drive, but it is probably a similar problem).  Replaced the fuse and the car would want to start, but blew soon after.

[silverton]

5 hours ago, nvrgnadi said:

 the fans not shutting off for any reason is a pretty clear indicator of the ecu being compromised

 

 

Nope.

On 11/21/2024 at 1:24 AM, nvrgnadi said:

The temp gauge also jumps right to “hot” as soon as the key is turned to the“on” position. 
 

There are a few codes that are showing 

Coolant temp sensor 

 

 

This is why your fans are turning on full speed when you key on.  When there is a DTC present, or AC switch on, this happens. The failed coolant temp sensor and/or circuit is what is causing your instrument panel needle to go full hot.

I would only be concerned about TSB 09-43-06 if you clear(fix) your DTC and your fans still continue to run continuously even with the A/C switch off.

[tysparks81]

47 minutes ago, silverton said:

Nope.

This is why your fans are turning on full speed when you key on.  When there is a DTC present, or AC switch on, this happens. The failed coolant temp sensor and/or circuit is what is causing your instrument panel needle to go full hot.

I would only be concerned about TSB 09-43-06 if you clear(fix) your DTC and your fans still continue to run continuously even with the A/C switch off.

This can is true for the temperature needle and fans running, but those things wouldn't keep the car from starting.  You can test this by unplugging the fans or the coolant temp sensor and the car should still start. 

But I will wait for the OP to confirm that he has a blown IGN fuse under the dash.   As it will account for the not starting, but not the cause of what is tripping the fuse which needs to be addressed first though.  But I have been wrong before.

 

[silverton]

cold start fueling logic is based in part on temperature of coolant, if it thinks it's hotter than hades (needle pegging H) it wont have the right mix to even try to puff puff puff anywhere on earth.

[nvrgnadi]

The car will start and idle but not with out a little aggressive fueling.

All while the temp gauge is slammed to hot.

I did replace the coolant temp sensor (aftermarket) although I dont think the original was ever bad as Ive bench tested it and it seems to work fine. Since then I've put the original sensor back into the car as I saw no change with the new/aftermarket one.

So the Car will run, rough at first, but once it gets its legs underneath it it seems to idle fine.  

Keeping in mind the cooling fans are running the entire time, full speed, along with the gauge pinned at HOT!

Id imagine if the gauge is hot the computer is a assuming it's running "HOT" so it's making all sorts of adjustments or changes to the general performance in it's efforts to limit the car from self destructing or hurting itself from running "HOT" so to speak. 

This is just my assumption as I dont know for sure. 

 

I buy a new battery today as the old one was barely holding a charge long enough to test diagnose anything without the engine off.  I wonder if maybe... possibly.... it was a lack of Voltage causing these issues.  I doubt it but either way the new battery will be in soon.

One other thing Im wondering is... stay with me here:

In the early days of this issue I had to replace the factory harness side connectors on the coolant temp sensor (car side) and the vapor purge solenoid (car side) as they just happend to be right there and were beat up and broken from being 20 yrs old etc.  No big deal.

When I re assembled everything I had accidentally swapped the vapor purge solenoid connector with the coolant temp sensor plugs (wrong sensor to wrong harness plug) btw this definitly will make the car NOT run... ask me how I know),  odd that subaru put two connectors so close together that were nearly identical and would fit if swapped... just odd anyhow.   

So now, maybe im second-guessing myself, but I'm wondering if I possibly messed up the wiring on one or both of the sensors/solenoid.  

I've looked at diagram after diagram and none of the ones I've looked at correlate with the factory wiring diagrams wire colors that should be present for each of the items.  

If anyone can clearly spell out to me what they should be and where exactly on the sensor side the pin order should be id appreciate it a lot!  Cant hurt in asking. 

 

At this point i have the ecu out and am just checking the wiring again to make sure I have not overlooked something stupid like a pinched wire or a broken connector etc between the ecu and the sensor or fans.

i'll write down which colors are what for the two connectors and report back.

 

Thanks again everyone for all the help!!

 

 

 

 

 

[nvrgnadi]

Forgot to mention - I did unplug the fans and have had the coolant temp sensor unplugged at the same time and when I do this the temp gauge still pins to HOT and the car runs. 

Edited Thursday at 09:53 AM by nvrgnadi

[nvrgnadi]

Update…  installed new battery … high hopes… no difference.  
 

but when messing around today once I got the car to idle,  using a scan tool I decided to see what would happen if I cleared the code which was the only code “a high circuit value for the Cts”.  The moment I did this like to the else one the car began to purr like a kitten… then a second later when the computer realized something was likely off with the sensor or circuit or related to ,  the car ran much shittier.   But what it tells me I think is that it’s not the computer it’s the CTS circuit.

Am I in the right ballpark with this thinking?