maverickfhs

So today I was driving down the road and CEL came on my 06 Civic EX with AT, after scanning the code it's P0128.

Usually temperature gauge on the ODO shows 3-4 dots on the highway and they rise to halfway, once I am in stop and go traffic.

I was literally thinking about it, that there's possibly a problem with T-stat since it was brutally cold in last few days and car was usually showing 2-3 dots on highway, but NO CEL.

I think thermostat is stuck open and needs to be replaced, that's why a CEL. Anyone has any other ideas or advice?

Thanks very much.

ezone

Three possible and common issues come to mind right away:

1) Bad thermostat/low coolant/wrong concentration

2) the temperature sensor in the bottom of the radiator may go bad or become inaccurate, also common is loose and corroded wire terminals for that sensor causing high resistance and skewed reading by the PCM.
(Rodent damaged wiring is common in my area too.)

3) Software update for false P0128 code.


For info on #2 and 3, see the TSB in this link: http://noes.net/09-092.pdf

maverickfhs

Thanks EZ, here are my thoughts and response. What's your advice?

1-I am suspecting bad T-stat, it has Honda Type 2 50/50 in it. Coolant is good and full, check radiator and reservoir too.

2- Not sure about it?

3- Car has been maintained at the dealer until 2016, is there any latest/recent update for software and how can I make sure it's not software? BTW, my key fob randomly doesn't work which I suspect is bad battery, in one of the forum thread noticed someone saying it's due to software issue, no idea though?

maverickfhs

P.S: Don't you think that lower dots on temp gauge are also pointing to a bad T-stat?

ezone

1, 2: The code generally points to a thermostat, but that's not the only possible issue represented by the fault code.

Those other issues mentioned that result in the same code have been equally common IMO, if not more common.
That TSB I linked, did you read it?

If no obvious issues are found with the radiator temp sensor, then you might toss a Honda stat at it. (I don't like aftermarket)


Looked at the troubleshooting guide for P0128.....In my mind I'm reading and mentally calculating how much time they want to waste...when instead you could toss a stat in it in 10 minutes and see if the code stays gone LOL

3) We are not supposed to just do software updates without a reason, so unless software was updated to address some other issue in the past, there's a good chance it may not be current.

The dealer level scanner can display the current software version installed for engine and transmission, and if it matches or is newer (higher) than what's listed for your particular car in the linked bulletin, then an update won't help this issue..

PS) Not necessarily. Dots don't tell the actual temperature in degrees, and the gauge display is heavily buffered.

Most scanners and apps will show you a value for ECT1 which is the temp sensor in the engine, but few can display the temperature value for ECT2--that's the sensor in the radiator.

maverickfhs

Yes, I did read it. Thanks for sharing TSB.

For now, I am planning to put a new T-stat and see what happens. Do you think it's a sensible move(https://www.civicforums.com/forums/1...-question.html, https://www.obd-codes.com/p0128)? Since I think car still has original T-stat.

BTW, can I restart ECU by removing -ve cable and see what happens? I mean, how long it'll take for the code to come back again.

Is there anything particular I should be aware of while replacing T-stat, seems fairly straightforward.

maverickfhs

One more thing, can I test ECT1 and ECT2 sensors and corresponding temps with any OBD scanning tools? Like I can get from autozone and these places as a rental/loaner one?

And can ECU be upgraded(if it's needed) without a dealer or no(http://www.8thcivic.com/forums/mecha...28-code.html)?

Not sure, why 2 part numbers? https://www.hondapartsnow.com/oem-ho...75234&Filter=()

ezone

I just googled the bulletin, I don't ever link service info directly but I will google search and link info I find that others have posted on the net
A service bulletin never means a repair will automatically be covered by warranty.
Warranty only covered a repair if the car was "in warranty" at the time the repairs were needed.


As I already said, I'd be checking the condition of the wiring and temp sensor in the bottom of the radiator first.

But yeah, the stat is quick and easy to change. I'd use a stat from Honda myself, despite the price--I know I can depend on the quality. Battery disconnect will erase PCM fault codes....and lock up your radio if it is an anti-theft type. Make sure you have your unlock code handy.


You don't have your own code reader? I thought all code readers will also erase codes.


Factory unit is simple...Unbolt and remove.
Wrap the new gasket around the new stat the right direction,
Make sure the jiggle pin is centered in the gap,
Insert the assembled stat with gasket in the hole with the jiggle pin at the top.
Assemble, fill, burp cooling system.
Literally 10 minutes or less, not including time for warming up the engine afterwards and cleanup.
Carry on with life, knowing the factory unit is probably gonna last another 100-200k miles. If the code comes back, you can be pretty dang sure it's not a bad stat.

Installing an aftermarket? Too many possible ways to go wrong for me to guess LOL (I've seen a lot over the years)
If you install one and the code returns, you won't really be assured it's not a faulty new stat---instead of any of the other possibilities.

(I once installed a trusted well known brand aftermarket thermostat in a freshly rebuilt engine in one of my old GM cars. Stat opened about 40 degrees too early, had no heat on the first test drive--and it was winter. 2nd stat, same brand, lasted less than 3 months.)

maverickfhs

Thanks so much EZ, as usual.

Actually, I do have unlock code for the radio but I'll try to erase the code from OBD scanner.

My plan of action is to put the car on jackstands and see the bottom sensor and it's wiring, I might as well clean it and put some dielectric grease on it and top sensor too.

Definitely going OEM, at least one less thing to worry about! I am planning to pull trigger on either of these two: ( ) OR (https://www.ebay.com/itm/Genuine-OEM-Honda-Civic-Thermostat-w-Gasket-2007-15-EXC-Si-Hy-19301-RNA-315/112645816375?hash=item1a3a36c037:g:uDkAAOSwldRaD2Jm:sc:USPSFirstClass!20109!US!-1&vxp=mtr)

Actually for anyone also 'looking or searching' here's one helpful and very detailed video:
Not made by me. Lol

I'll report back in a few days, weather here is brutally cold. DANG!

maverickfhs

Thanks so much EZ, as usual.

Actually, I do have unlock code for the radio but I'll try to erase the code from OBD scanner.

My plan of action is to put the car on jackstands and see the bottom sensor and it's wiring, I might as well clean it and put some dielectric grease on it and top sensor too.

Definitely going OEM, at least one less thing to worry about! I am planning to pull trigger on either of these two: ( ) OR (https://www.ebay.com/itm/Genuine-OEM-Honda-Civic-Thermostat-w-Gasket-2007-15-EXC-Si-Hy-19301-RNA-315/112645816375?hash=item1a3a36c037:g:uDkAAOSwldRaD2Jm:sc:USPSFirstClass!20109!US!-1&vxp=mtr)

Actually for anyone also 'looking or searching' here's one helpful and very detailed video:
Not made by me. Lol

I'll report back in a few days, weather here is brutally cold. DANG!

ezone

All scanners and apps that provide a datalist should be able to display ECT1.

But from what I have seen, few scanners display data for the radiator temp sensor (ECT2).


I think you're gonna be hard pressed to find an independent shop that can do factory software updates (also called "reflash") to the PCM. An indy shop providing that level of service is likely to be a specialty shop competing directly with the dealership, and is likely to be as high or higher than the dealer.

Looks like the part number superceded. -315 looks like the newest part number, but the other number may be sold until stock is depleted.

maverickfhs

As always, makes sense and thanks so much EZ.

I'll try to analyze the data first and then see what happens, will update the thread.

Again, thanks for confirming the part number too, Honda(Or can I say CAR)GURU

maverickfhs

By any chance, does anyone know if they both are same?

https://www.ebay.com/itm/Genuine-Hon...!US!-1&vxp=mtr

https://www.ebay.com/itm/Genuine-Hon...!US!-1&vxp=mtr

Because it looks like all dimensions and everything is same, I have one laying around from an older accord.

ezone

No clue here, all I can see if different part numbers.

What's the temp rating on it?
Compare to the right one for your car

maverickfhs

Thanks EZ. I believe it's 180.

Another way I compared it, I actually went to Rock Auto website and it's listing same T-stat for my older Accord, as well as 06 Civic. Also, showing part numbers exchangeable too. Like 19301-PAA-306 and 19301-RNA-315.

But I wanted to be sure, even dimensions are same too.

But I wanted to play safe

ezone

Stat for an older car might be stamped 82*C (180f) on the bottom......

newer cars might need to be 88* or 90*C (190-195f)
Check yours?

My own car runs steady 202f on highway trips (ultragauge), I think its stat is stamped 88 (I CRS, LOL)

maverickfhs

I'll simply order a new one. Just making my life complicated and can always use that one as a backup! Lol

Thanks again for your help.

ezone

I seem to do this to everyone LOL

maverickfhs

It was me, who's making my own life complicated

maverickfhs

BTW, T-stat for older accord is 77 degree Celsius or 170 in Fahrenheit.

So no bueno and ordering an OEM for 06 Civic.

Curious minds never stop, lol

Now question, have you heard of Aisin thermostat, as well as Tama Thermostats for Honda?

http://www.rockauto.com/en/moreinfo....588308&jsn=148

https://www.ebay.com/itm/Honda-Tama-...5/251512991496

maverickfhs

Are Aisin and Tama OEM suppliers or no? It's just Nippon and Fuji? Thanks for the help

ezone

I couldn't tell you what the brands are unless the parts catalog says it.

maverickfhs

Gotcha and it never mentions anything for Aisin or Tama, so far

maverickfhs

So it looks like older Accord one is not OEM either, because OEM supposed to be having 78 degrees Celsius and 8th Gen Civic is 82 degrees Celsius, always something new to learn. Although dimensions and everything apparently is same!

maverickfhs

Honda OEM T-stat is on it's way.

Can I drive occasionally like that or would I destroy O2 or Cat or anything?

ezone

You've been driving it this way already, haven't you?

maverickfhs

Nope, car is parked since the day I found out about it. Although I drove a few miles after CEL came, since I was already out and about.

ezone

If the stat is really faulty it's probably going to run below operating temperature (if you drive long enough to reach it in the first place) or take longer to warm up than it should.

Right now it's below +3F here, I can drive all over town and never reach operating temperature. I did just that on the way home from work (+6F), a good 40 minutes of driving in town (under 35 mph) and the engine never got above 165f.
But it's because I have the heater fan on full blast, and the heater pulls heat out of the engine faster than it can burn gas to make heat. I have to hit the highway or run it at high RPM, or turn my heater off before it will reach operating temp.

maverickfhs

That's exactly the situation here too, brutally cold.

I'll keep the car parked and only drive after replacing T-stat and then see what happens and hopefully no more CEL. Otherwise, more troubleshooting.

maverickfhs

Replaced T-stat with an OEM and definitely happy!!!

No more CEL and all is well, drove nearly 15-20 miles after clearing the light and all is well.

Hopefully it'll stay like it. Thanks for all the help EZ, as usual