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Offline Tumaca

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ECT sensor
« on: 29 May, 2020, 12:10:45 PM »
I would to ask if someone know why an ECT sensor could be damaged.

I am asking this because of my MK2 is at the Honda delaer to change that sensor... and this is the 4th time in one year. They say the sensor is faulty because is under 2,3ohm and the guide or manual or whatever says that is an abnormal value.

All other stuff/sensors are showing nominal values, but is hard to believe that a sensor can be damaged so many times and without reason.

As consecuence of this problem, the fan does not kick in sometimes and the hot temperature led blinks.


Thank you.

Offline Art

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Re: ECT sensor
« Reply #1 on: 29 May, 2020, 03:45:00 PM »
Well all things can fail and ECT sensors are no exception but 4 times in 12 months is not acceptable, should not happen and I've never heard of anything like it. Coming from a Honda Dealership I'd expect to have parts, labour and diagnostic warranty, after all you've consulted the 'professionals'. If I was a gambling man I'd wager they've either incorrectly diagnosed the fault or supplied faulty/incorrect specification parts.

I'd insist the dealer replace the ECT sensor under warranty (parts and labour) and having completed the work insist they check the sensor resistance and that the fan and coolant temperature lamp operate as normal. Out of curiosity I'd ask what the actual resistance of the failed sensor was and at what temperature the resistance was measured. The Honda Workshop Manual gives the specification for the ECT sensor resistance as
2.1 to 2.7 kΩ at 80°C in Section 1, General Information page 13
2.3 – 2.6 kΩ at 20°C in Section 5, Fuel System (PGM-FI) page 25.

If you haven't already download the Honda SC64 (MKII) Workshop and Owners Manuals here

« Last Edit: 29 May, 2020, 03:51:00 PM by Art »

Offline Shed

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Re: ECT sensor
« Reply #2 on: 29 May, 2020, 06:29:26 PM »
4 in one year?

As Art's  :0461:

Plus:

Your Honda dealer have a bad batch of the correct ECT sensor in stock.

Your Honda dealer is fitting the wrong ECT sensor.

It is not the ECT sensor itself but the wiring block connector and/or the wiring on the loom side of the bike, and it is this faulty wiring that is causing the sensor to fail prematurely.


Offline Tumaca

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Re: ECT sensor
« Reply #3 on: 29 May, 2020, 06:45:51 PM »
First of all, thank you for your answer.

All repairs (from the second to this) are free of charge for me. The dealership was in contact with Honda Spain explaining that this sensors was changed several times in this motorbike but their (Honda Technical Department) instructions  are "replace the sensor".

The last time, the dealership showed to me the "to do list" in the computer (all the checks you have listed) and with the old sensor and a multimeter we did step by step. The result, regarding the workshop manual, is "faulty sensor". If i am not mistaken, the value was 1.8

But four months later again the same problem: no fan so temperaure light on. Go back to the dealership and hey! Faulty sensor again (the value is under 2.3) and the ECM has an error in the ECT circuit.

And here I am, asking how can be this possible. Honda (and I mean HONDA, not the dealership) say that if the value is incorrect the sensor must be replaced and so on the times that are needed.  :084:

And if that is not enought, seems that Honda is moving it stock from Belgium to Barcelona and right now there are huge delays in the orders (one week later the dealership is still waiting for the sensor)
« Last Edit: 29 May, 2020, 06:55:09 PM by Tumaca »

Offline jm2

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Re: ECT sensor
« Reply #4 on: 29 May, 2020, 11:22:45 PM »
The ECT is a 3-pin affair with the 'temp lamp' on it's own channel (separate thermistor maybe?) as a sort of last chance warning (i.e. the ECU hasn't got the temperature under control for some reason).

I'd be checking the fan and the fan control relay (in case of poor contacts or intermittent operation) next as I suspect the ECT (being the fourth one) isn't actually the problem.  Indeed, that would be my first port of call at seeing the (elusive to me) red lamp.

Starter solenoids apart, do Honda have a whole run of duff parts ??  Thinking that they'd only keep one or two in stock at best and reorder from Belgium? with new (alternate) stock. 
Only do it right - no bodging please.   Keeper of the failed stator list.   John.

Offline Tumaca

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Re: ECT sensor
« Reply #5 on: 30 May, 2020, 12:46:09 AM »
*Originally Posted by jm2 [+]
The ECT is a 3-pin affair with the 'temp lamp' on it's own channel (separate thermistor maybe?) as a sort of last chance warning (i.e. the ECU hasn't got the temperature under control for some reason).

I'd be checking the fan and the fan control relay (in case of poor contacts or intermittent operation) next as I suspect the ECT (being the fourth one) isn't actually the problem.  Indeed, that would be my first port of call at seeing the (elusive to me) red lamp.

Starter solenoids apart, do Honda have a whole run of duff parts ??  Thinking that they'd only keep one or two in stock at best and reorder from Belgium? with new (alternate) stock.

The fan relay was the first thing I changed a year ago with no result.
The fan, when the sensor is between its nominal values, kicks in/out correctly.
If I am not mistaken, the red lamp receives data directly from the thermostat. As you said, is a separate circuit.

The fact is the sensor is showing wrong values (is true if you go to the workshop manual and read the values) and Honda is not going to move to the next step until the error (red lamp) happens AND the ECT values are nominal. What they do is follow the "to do list". In that list, the ECT is one of the first so if its values are abnormal Honda replace it and that is all. Is like a loop (a crazy one).

Everytime the ECT sensor has been changed everything works great... until 2,3 or 4 months later when one day, in some traffic light, in some street the red lamp says "hello! Do you remember me? I am your nightmare" :157:

I remember that the second time this happened and after replacing the ECT the dealership checked all the wires from ECT to ECM to Fan relay to fan (and the wires under the fuel tank): all was OK. They also checked others things with the diagnosis tool and everything was in factory values.

So either my mk2 has a leprechaun or there is a bad ECT batch (and I am taking all of them.. Maybe should I buy some lottery? ) or there is a wire in some place, in some connector (could that damage a sensor?)... because I cannot understand this. My hope was that someone in this forum had heard something similar.

To be more specific: what can damage a sensor? ONLY one sensor and no others. If more sensors were affected then I could understand something is wrong (voltage, for example), but only and always the ECT?? I have never seen this before.
« Last Edit: 30 May, 2020, 01:21:51 AM by Tumaca »

Offline jm2

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Re: ECT sensor
« Reply #6 on: 30 May, 2020, 04:26:17 PM »
Or the ECT sensor is working fine and your bike really is overheating.

How are the coolant levels ?  (main cap full, expansion reservoir at the correct levels hot/cold).
Steps after that; radiator clear (internally and externally), water pump condition.
Only do it right - no bodging please.   Keeper of the failed stator list.   John.

Offline Tumaca

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Re: ECT sensor
« Reply #7 on: 01 June, 2020, 11:15:39 AM »
*Originally Posted by jm2 [+]
Or the ECT sensor is working fine and your bike really is overheating.

How are the coolant levels ?  (main cap full, expansion reservoir at the correct levels hot/cold).
Steps after that; radiator clear (internally and externally), water pump condition.

The ECT value is incorrect, so there is a problem with it (said by Honda). The question is: why so often?

All levels are at their maximum. Overheating only occurs when there is no fan, and the fan does not kick in when the ECT fails.

With the red light on, if I have some free street ahead to get up to 2nd or 3th gear at 2.500-3.000rpm the red ligh turns off in a few seconds. That means the coolant, radiator and water pump are doing their job (I think).

Resume:

ECT value is incorrect
Fan does not kick in
Red ligh on

ECT value is correct
Fan kicks in
No red light
« Last Edit: 01 June, 2020, 11:22:23 AM by Tumaca »

Offline jm2

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Re: ECT sensor
« Reply #8 on: 01 June, 2020, 11:49:42 PM »
But if *any* of the other things that cause the fan not to cool sufficiently (or even run at all) are present/faulty then the exact same scenario exists even if the ECT sensor is correct.

Fan control relay and its holder and associated wiring input and output,
Fan fuse A and its wiring - NB. This doesn't seem to feed anything else (a dicky fuse?)
Fan supply itself
The coolant and flow,
ECT feed to ECU wiring,
The ECU itself (well more likely P13 on the grey plug, P31 on the black plug or the intermediate connector 12P black).

So you'll need to know what is the state of play when you have the fault.
Is the fan relay being operated (or intended to be) when overheating (lamp on)
The water temperature - may temporarily fit one of those thermometer leads in the upper hose ?

Is the fault (now) a hard fault ?   i.e. if you used it today will it show overheat soon enough.
Only do it right - no bodging please.   Keeper of the failed stator list.   John.

Offline iNCORRIGIBLE

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Re: ECT sensor
« Reply #9 on: 02 June, 2020, 12:08:57 PM »
Good stuff Jm2.Faulting is clearing each item conclusively exactly as you are suggesting.I had a fan relay that operated correctly but output contacts were intermittent.Ed. :028: p.s. I also put a temporary indicator light across the fan to show when it was energised to check for reliable,consistent operation.Ed.
« Last Edit: 02 June, 2020, 12:54:54 PM by iNCORRIGIBLE »
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