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Discussion Starter · #1 ·
Hello everyone, I am here as a last ditch effort to try to figure out my best course of action and need you all's help! I have a 2012 Civic LX, that I bought used and nothing for bells and whistles. Pretty standard run of the mill. I started having an overheating issue where after the engine runs for about 30 minutes (give or take a few minutes depending on outside temp) the car overheating light begins to blink and at times goes all the way to the "water temp hot" alert on the dash. My repairs at first were, changed water pump, radiator flush, changed thermostat, and changed ECT sensor on top of the engine. Still overheating
I took it to a mechanic at this point and he indicated it was probably an ECU issue that was not communicating to the engine for the fans to turn on. He did not want to do the repairs because he is a smaller shop and did not want to tie up his lift. For the ECU, he said I would have to get the part and then it would have to be programmed by a mechanic or the dealer. Obviously, lots of mechanics in our area are 2-3 weeks booked out. My dad came to visit and stepped in to help and we did some further investigation. He did confirm that the fans do not appear to be turning on when they should, intermittently they engage at a higher RPM, but not in the normal course of driving. The lower ECT sensor on the radiator was changed, the AC was appropriately pressurized, the radiator ECT sensor wire was changed, the ECU was reset, the MAP sensor was cleaned, relays and fuses tested. At the end of the day, we are still overheating in the same way as before.
I have used an engine block tester to make sure I haven't cracked a head gasket, which I have not. But at the end of the day it does seem that it may be an ECU problem as we are left with no other alternatives that we can come up with.
Where I need the community's help is this.....
#1-Is there any other cheap fix, I can try?
#2- Is there a way to avoid $800-$1000 on getting a new ECU? Where can I find one second-hand online and does it in fact need to be programmed at a mechanic or is there some online place I can send away and hotswap the ECU to save some money.
Any help is appreciated. Like I said, I am at my wits end and would rather not have to drop $1,000 to get my commuter car back on the road.
Thanks everyone!
 

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It is highly unlikely the ecu has failed.

What other troubleshooting have you done on the fans? Is a signal being sent to the fan but it is not turning on? Do the fans turn on when you turn on the AC?

Do the fans themselves work? Have you tried jumping the fan switch to see if they turn on then.

A proper diagnosis on the fan circuit needs to be completed. So far you have just changed parts not knowing the real issue. My bet is that a new ecu will not fix the problem.

Sent from my SM-G973U1 using Tapatalk
 

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Discussion Starter · #4 ·
It is highly unlikely the ecu has failed.

What other troubleshooting have you done on the fans? Is a signal being sent to the fan but it is not turning on? Do the fans turn on when you turn on the AC?

Do the fans themselves work? Have you tried jumping the fan switch to see if they turn on then.

A proper diagnosis on the fan circuit needs to be completed. So far you have just changed parts not knowing the real issue. My bet is that a new ecu will not fix the problem.

Sent from my SM-G973U1 using Tapatalk
The fans do turn on when the AC gets turned on. That seems to be a way to force the fans to turn on, but after a while it still overheats. The fans do work and we did jump the sensor at the bottom of the radiator to turn on the fan and that seemed to work. we also had an extra sensor that we plugged in and warmed up with a torch which turned on the fans, but when everything gets plugged in as it is supposed to be it still overheats.
Fan circuit diagnosis...got it. What would be the process for that?
Thanks for the help and response
 

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Here's a basic schematic of the fans on your car.
Comprehensive interactive troubleshooting can be found in Honda Service Express. (see my sig line)
You will have to pay to access this site.

Have you checked the actual coolant temperature when the "High Temperature Indicator" indicator is on?
 

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The fans do turn on when the AC gets turned on. That seems to be a way to force the fans to turn on, but after a while it still overheats. The fans do work and we did jump the sensor at the bottom of the radiator to turn on the fan and that seemed to work. we also had an extra sensor that we plugged in and warmed up with a torch which turned on the fans, but when everything gets plugged in as it is supposed to be it still overheats.
Fan circuit diagnosis...got it. What would be the process for that?
Thanks for the help and response
You have a short somewhere and the fans aren’t kicking on. However if you don’t have Honda ids, that’s where I would start. If you had Honda IDS, you would use the computer and tell the fan to kick on. If the ecu isn’t doing that, then you have another problem.


Sent from my iPhone 13 Pro while on the toilet.
 

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You have a short somewhere and the fans aren’t kicking on. However if you don’t have Honda ids, that’s where I would start. If you had Honda IDS, you would use the computer and tell the fan to kick on. If the ecu isn’t doing that, then you have another problem.


Sent from my iPhone 13 Pro while on the toilet.
HDS?

My foxwell bidirectional scanner also does this.

a HDS kit can be had from these guys for around 100 bux, will need the laptop.


They work, but much prefer the foxwell, less cludgy than a laptop and all those cables.
 

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HDS?

My foxwell bidirectional scanner also does this.

a HDS kit can be had from these guys for around 100 bux, will need the laptop.


They work, but much prefer the foxwell, less cludgy than a laptop and all those cables.
great find on the him tool
 

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great find on the him tool
you need to piss about a bit with the software and the serial to usb interface and drivers, but it does work well.

I dedicated an old laptop to these tasks, since who the hell knows whats in that tweaked software.

always good to have a bish laptop for those sketchy things.
;)
 

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you need to piss about a bit with the software and the serial to usb interface and drivers, but it does work well.

I dedicated an old laptop to these tasks, since who the hell knows whats in that tweaked software.

always good to have a bish laptop for those sketchy things.
;)
I know a guy that worked @ AHM and he said the same as you.
And, that a foxwell product would be a better choice for dyi people.
 

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Discussion Starter · #11 ·
You have a short somewhere and the fans aren’t kicking on. However if you don’t have Honda ids, that’s where I would start. If you had Honda IDS, you would use the computer and tell the fan to kick on. If the ecu isn’t doing that, then you have another problem.


Sent from my iPhone 13 Pro while on the toilet.
I am fairly certain that is what the mechanic did. He used his computer to force on the fans and that seemed to work and take away the issue. Still not sure what that means tho. I will try to get a reader.
 

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Discussion Starter · #12 ·
you need to piss about a bit with the software and the serial to usb interface and drivers, but it does work well.

I dedicated an old laptop to these tasks, since who the hell knows whats in that tweaked software.

always good to have a bish laptop for those sketchy things.
;)
Windows 7 ok or does it have to be 10 or 11?
 

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Windows 7 ok or does it have to be 10 or 11?
The Windows-10 Professional is currently the only supported software for the Honda i-HDS, but the older HDS will work with Windows-7 SP3 or Windows-8. The Windows-11 Professional version is not supported at this time.

Here's the latest version software for free-download for the Honda HDS & i-HDS diagnostic tools.

Free Download Honda HDS 3.104.042+iHDS 1.006 +J2534 Rewrite | OBDII365.com Official Blog

Honda HDS diagnostic tool.
 
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