P500 P500 temp guage

[DG Rider]

And for the record in my experience ECU's 99.9999% of the time they either work fine or they don't at all, not just one feature like the temp sensor input goes out. Wires or sensor...

I agree. Usually (but not always) a bad ECU does all sorts of weird things and often sets multiple codes.

The sensor is easy enough: Check the resistance. I'd suspect rodent damage, personally, but a ECT is not uncommon.

 

[Duckhunt]

I guess I'm confused about what you're saying...

You said...

I'm saying that if you unplug one on a perfectly healthy machine with no issues, it will ALWAYS start the fan and set a code.

LOL this isn't a perfectly healthy machine! So if we unplug it, it codes the fan remains on which I believe you, it'll act like a perfectly healthy machine that has the sensor unplugged! Then in this same scenario you plug the sensor back in and the temp gauge goes to high (we can just ignore the fan at this point because it seems to be a constant on either way) now we don't have a perfectly healthy machine! So it acts like a normal healthy machine should with the sensor unplugged but acts up with it plugged in. One variable there.

If it doesn't do anything with it unplugged then something else is causing it!

 

[Duckhunt]

@DG Rider I'm with you man! I just troubleshoot hydraulic and electric schematics every day all day and most people that contact me can't do an ohm test or read a schematic. So you find ways to do "unplug this and tell me what happens... then change this relay with this relay if nothing happens... then run a jumper wire from here to here and tell me what happens..." when a ohm test would solve A LOT!!!

 

[DG Rider]

LOL this isn't a perfectly healthy machine! So if we unplug it, it codes the fan remains on which I believe you, it'll act like a perfectly healthy machine that has the sensor unplugged! Then in this same scenario you plug the sensor back in and the temp gauge goes to high (we can just ignore the fan at this point because it seems to be a constant on either way) now we don't have a perfectly healthy machine! So it acts like a normal healthy machine should with the sensor unplugged but acts up with it plugged in. One variable there.

If it doesn't do anything with it unplugged then something else is causing it!

OK...one more time...

Unplugging the ECT will...
a) Cut on the cooling fan
b) Cause the temp gauge to read full bars
c) And set a f***ing code

Healthy machine. Unhealthy machine. Doesn't matter.

This machine is ALREADY DOING THIS, so you've accomplished nothing by unplugging it. Your proposing that he "test" using an action that provides the exact same symptoms he already has, which makes it pretty tough to determine anything from it.

 

[Duckhunt]

OK...one more time...

Unplugging the ECT will...
a) Cut on the cooling fan
b) Cause the temp gauge to read full bars

Healthy machine. Unhealthy machine. Doesn't matter.

This machine is ALREADY DOING THIS, so you've accomplished nothing by unplugging it. You proposing that he "test" using an action that provides the exact same symptoms he already has, which makes it pretty tough to determine anything from it.

I thought you said it would code with it unplugged. Sigh.

 

[DG Rider]

I thought you said it would code with it unplugged. Sigh.

I'll edit it...just for you...

 

[70Bones]

OK...one more time...

Unplugging the ECT will...
a) Cut on the cooling fan
b) Cause the temp gauge to read full bars
c) And set a f***ing code

Healthy machine. Unhealthy machine. Doesn't matter.

This machine is ALREADY DOING THIS, so you've accomplished nothing by unplugging it. Your proposing that he "test" using an action that provides the exact same symptoms he already has, which makes it pretty tough to determine anything from it.

DG Rider, don't take this the wrong way, I'm just wondering if you are sure about this, as the Honda ECT sensors seem to have a negative coefficient, which means when you unplug it, resistance goes to infinity, telling the computer the temperature is very low. I tried to find the curve for that particular sensor but could only find Honda sensors in general.

 

[DG Rider]

DG Rider, don't take this the wrong way, I'm just wondering if you are sure about this, as the Honda ECT sensors seem to have a negative coefficient, which means when you unplug it, resistance goes to infinity, telling the computer the temperature is very low. I tried to find the curve for that particular sensor but could only find Honda sensors in general.

100% sure.

A confession:
During this debate, i knew the fan/code thing was right, but i hadn't really paid any attention to the temp gauge behaviour (though i had an ideal), so i went out and tested on my machine. Unplugging the sensor and cutting the key on caused full gauge temp, cut the fan on after about 3 seconds, and CEL on. Could be that it compares it to IAT or oil temp (if it has one) and makes the determination from that. Or the range is just impossible.

 

[Neohio]

100% sure.

A confession:
During this debate, i knew the fan/code thing was right, but i hadn't really paid any attention to the temp gauge behaviour, so i went out and tested on my machine. Unplugging the sensor and cutting the key on caused full gauge temp, cut the fan on after about 3 seconds, and CEL on. Could be that it compares it to IAT or oil temp (if it has one) and makes the determination from that. Or the range is just impossible.

That is kind of why I thought wiring. A half chewed thru ground wire will be increased resistance, making ECM think It is super hot, but not an open circuit triggering a code on the dash.

 

[70Bones]

100% sure.

A confession:
During this debate, i knew the fan/code thing was right, but i hadn't really paid any attention to the temp gauge behaviour (though i had an ideal), so i went out and tested on my machine. Unplugging the sensor and cutting the key on caused full gauge temp, cut the fan on after about 3 seconds, and CEL on. Could be that it compares it to IAT or oil temp (if it has one) and makes the determination from that. Or the range is just impossible.

Can't argue with that! I'm just going by schematics and service manuals from my lazy boy chair, and adding my assumptions from years of troubleshooting in power.plants, which has taught me that hands on testing is definitely the best way. You rock!

 

[70Bones]

That is kind of why I though wiring. A half chewed threw ground wire will be increased resistance, making ECM think It is super hot, but not an open circuit triggering a code on the dash.

A fully chewed through wire would be the same as unplugging the sensor, putting the signal out of range, as DG Rider found out, and causing this issue. Don't want to hijack this thread, but how do we keep rodents from eating wire insulation? I'll start a new thread on this.

 

[DG Rider]

A fully chewed through wire would be the same as unplugging the sensor, putting the signal out of range, as DG Rider found out, and causing this issue. Don't want to hijack this thread, but how do we keep rodents from eating wire insulation? I'll start a new thread on this.

@lee shared a wire wrap that Honda makes to prevent it. Can't remember where it's posted, so maybe he'll chime in.

 

[lee]

Honda rodent tape, part #4019-2317
It's laced with capsaicin to deter chewing

 

[70Bones]

Honda rodent tape, part #4019-2317
It's laced with capsaicin to deter chewing

View attachment 103158

A derivative from hot chili peppers. I wonder if you can buy that in spray form?

 

[bender]

Right in front and a little higher than the spark plug. Unplug that SOB and if the fan stops and gauge goes down - or may possibly throw a code - you know it's the sensor. If it stays the same we'll look at the ECU, or PLC, or whatever Honda calls the "computer".

Thanks for your input. I will check it out this afternoon. I hope it is a bad sensor, computer sounds expensive! Thanks again Bender

 

[bender]

It jumps to max hot from cold after 5 or 10 minutes , occasionally it will take 20min.

Thanks everyone for your suggestions. I replaced the sensor and everything seems to be working fine. Y'all have been very helpful
Now i can enjoy this machine again
Bender out