Honda Civic 2011 (5D)
Hello,
I would appreciate help in locating a fault.
Yesterday while driving, my high temperature light came on. (Of course I pulled over and didn't continue driving)
Today I tried to understand what the problem was in depth and discovered a few things...
1. The A/C CONDENSER FAN doesn't work at all (I'm ordering a new one tomorrow)
2. The RADIATOR FAN is working but doesn't turn on by itself when the engine warms up.
The RADIATOR FAN only turns on if I turn on the A/C, it doesn't turn on by itself. (Even when the engine is at 100 degrees Celsius)
https://www.youtube.com/shorts/Rsc7z7BBdls
I also tried disconnecting the ECT next to the thermostat (ECT1 according to the schematic)
The engine made more noise like in the video but the RADIATOR FAN did not start working
I haven't checked fuses or relays yet.
I'm a bit lost with this...
There's also a reference table but I'm not sure what's in the table applies to my case
I would be happy if anyone could help or give direction.
fuses and relays should be step 1
cooling system troubleshooting procedures:
@imperator thank you for the response!
Besides Radiator fan relay and Fan control relay Are there other things that can be checked? I haven't seen precise instructions for such tests, I would be happy if you could guide me
check the link
@imperator Yes I saw it, thanks. I just can't decide which of the cases to start testing with
"Radiator and A/C Condenser Fan Low Speed Circuit Troubleshooting (With A/C)"
@imperator Today I replaced the AC fan (both work when I turn on the AC)
But they don't turn on when the engine reaches 100 degrees.
I want to check "Check for an open in the wire between under-hood fuse/relay box connector No. 3 terminal No. 4 and ECM connector terminal A5." But I'm not sure what the connector looks like and according to the drawings it's not really clear how to disassemble the fuse box.
I tried to take out the fuse box today, but it didn't go so well... The cables underneath didn't let me lift the box enough to see what was going on there.
which document are you looking at? Did you find the wiring diagram for the cooling system? I think the under hood fuse box connectors are named A to F
@imperator I'm using a local book that I have on my computer because I couldn't find the connectors on the website, but if you can check continuity on the relay's legs, then it's no longer relevant.
I want to check "Check for an open in the wire between under-hood fuse/relay box connector No. 3 terminal No. 4 and ECM connector terminal A5."
According to the diagram
( https://charm.li/Honda/2011/Civic%20L4-1.8L/Repair%20and%20Diagnosis/Engine%2C%20Cooling%20and%20Exhaust/Cooling%20System/Diagrams/Electrical%20Diagrams/ )
ECM A5 connects to F14 on the underhood fusebox.
F14 is connected to condenser relay pin 3 and fan control relay pin 3. So rather than disassembling the whole fusebox I would just probe using one those sockets.
@imperator Wow, thank you so much, you saved me! The link doesn't work... I opened the diagram and you are indeed right. The RADIATOR FAN RELAY and A/C CONDENSER FAN RELAY are internal relays (inside the fuse box itself so I don't have access to them) Can I check pin A4 on the electrical harness with pin 5 of FAN CONTROL RELAY and A5 with pin 3?
oops, the parentheses were getting jumbled into the URL. fixed now.
I couldn't find the connectors on the website
the charm manual for your car is shockingly good. I've never seen such a detailed and organised manual. It even has hundreds of photographs of component, connector, terminal and ground locations. All cross-referenced with each other and electrical schematics. Honda really went all out.
Anyway, connector views with wire colors are here:
https://charm.li/Honda/2011/Civic%20L4-1.8L/Repair%20and%20Diagnosis/#Diagrams/Connector%20Views/
@imperator I checked your link and Honda did go all out.. there's a remarkable amount of "views" supplied.
I have news and it's good! The problem was indeed with the thermostat
that's great to hear. And because you pinpointed the problem, you didn't have to replace any unnecessary parts. Thanks for reporting back.
FANL = low speed fans
@imperator Thanks for the guidance and for helping me focus! I know FAML is low fan ctrl... it's just always on but I think it's just an OBD error... Something else I noticed is my AC pressure... I couldn't find on the website what it should be... In my car it's between 100-120 psi with the AC off and 190-240 with it on... That sounds high
It's really strange to me that they work when I turn on the ac... but not when the engine is hot...
I'm afraid there is a problem with the ECM.🥲
@davi_d don't be afraid. use your multimeter to test if the ECM is sending the right signals. the procedure will be somewhere in the manual.
It's really strange to me that they work when I turn on the ac... but not when the engine is hot...
Why is that strange? That's exactly what a malfunctioning temperature sensor, or its wiring, would cause.
@chucktobias If I disconnect ECT1 like in the video... The engine noise changes but the fan doesn't start working... (So there is any reaction...even with obd I see the lowest value I have is -40)
https://youtube.com/shorts/Rsc7z7BBdls?si=CqhfwL6rhVfTSLSh
are internal relays (inside the fuse box itself so I don't have access to them ... and A5 with pin 3?
so if you keep following that circuit in the diagram, those pins I mentioned eventually come to fuse #15
Can I check pin A4 on the electrical harness with pin 5 of FAN CONTROL RELAY
so A4 on the ECM (Fan low control)?
according to the diagram it comes from F7 on the underhood fusebox. Inside, that's connected to Radiator fan relay pin 4 and 3 and fan control relay pins 3 and 5. continuing along, it leads to fuse 36 and also the previously mentioned A5 circuit (high fan control)
Got it, thanks! Can I just check these points (according to colors) or is it better to check all the options?
I don't understand your color system, but ...the diagram shows you what you are checking.
.
if you get continuity on pin5 then you know everything is ok up until that pin ( includes: the blue/purple wire in the harness, the radiator fan relay coil, and some internal connections.
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if you get continuity on pin 3/circuit A, then you know everything is OK up until pin 5, PLUS the fan control relay coil, etc.
.
The whole system is fairly simple. Finding the problem should be pretty straightforward.
@imperator This video helped me reduce testing... I can turn on the fans using OBD 2 sensors ECT1 and ECT2 are working. But fan low ctrl is always on https://imgur.com/a/CfpsUrr https://youtu.be/Uw4lLvyFOns?si=k3tYMmYH5xfBcu2B
Edit:
The sensor temp doesn't seem to be changing Either it's faulty or the thermostat is stuck closed
@imperator
Yes, it's the thermostat... One pipe is boiling and the other can be held without a problem This also explains why the fans don't turn on when they need to (because they don't know because ECT2 reads a value that doesn't require fans) But it still doesn't answer why fan low ctrl is always on and the fans aren't running...
So what was the result of following the troubleshooting steps for the fans?
Yes, it's the thermostat...
so test it
One pipe is boiling and the other can be held without a problem
the radiator hoses should be different temperatures. But if the difference is too great, then the radiator may be plugged, or the pump failed etc...
You drew your arrows the wrong way
@imperator thank you ❤️ If I take apart the thermostat I want to have the new one on hand because if it's bad I can replace it right away and if I'm already messing with it, shouldn't I replace it and be done with it?
What do you think about the fan ctrl low being on all the time(but fans not spinning)? Isn't that a bit strange?
you don't need to take the thermostat apart to test it. you can replace it if you want if you're confident the new one is of same or better quality. They're pretty reliable though and I've never needed to replace one in my life. And at least if you test it, you'll know for sure if it was causing a problem or it's a waste of time. If you keep guessing and throwing parts at an issue you don't learn as much.
I would have to look at the circuit again, but even if the ECM signal is enable, the fan won't spin unless the relays and switches are on as well. I think ... no?
@imperator Well maybe you're right... If the thermostat works I won't replace it... Regarding the fans, isn't the ECM what activates the relays and switches?
so if fan low signal is on, maybe the ECM is getting bad information. Did you check the sensors?
@imperator Which sensor? What I see in OBD is not what the ECM provides?
the sensors that are on the electrical schematic I posted above. I don't know what you see. Again, there are troubleshooting steps in the manual for testing EVERYTHING related to your cooling system. Follow them, to the end, and let us know what you found.
@imperator I have news and it's good! The problem was indeed with the thermostat. I took it out and checked it and it didn't move at all in hot water it was stuck closed... After I replaced it the fans turn on (apparently in FANL (because when I turn on the ac it shows FANH in the obd and they are also noisier)) They turn on when ECT2 reaches 94 degrees or when it reaches 0.55V And they turn off when it drops to 87 degrees Why does the obd keep calling FANL? I don't know
@imperator
The website https://charm.li/ stopped working suddenly. Do you happen to know if there is any problem?
I can’t access it either
According to the diagram
1. If the key is in position ll there is voltage to RADIATOR FAN RELAY on pin 3 and FAN CONTROL RELAY on pin 5.
2. If FAN LOW CTRL is on, there is ground at point A4 and it closes series circuit that starts at point A and ends at B where both fans should work at low speed.
I don't see a way in which anything here could be faulty if the 2 fans work in FAN HIGH CTRL when it is on and are off when it is off What do you think?
I hope my diagram is understandable
@davi_d notice that with FANL the fans run in series with each other. Each only sees 6V. In FANH they are isolated on their own circuits and see the full 12V. You need to test each component. If the ECM signal was on all the time it could have burned something out. That's what the troubleshooting steps in the manual are for. They were designed for technicians to pinpoint the problem as efficiently as possible. Let us know when you have completed all of them. By then you should have a solution.
You're right... Wouldn't it be a better idea to first understand why FAN LOW CTRL is on to prevent the fans from spinning all the time when I find the problem?
And what would you recommend starting the diagnosis with? With that?