Error code P0128 - cooling system issue

Discussion in 'Honda Hybrids' started by cylverbak, Dec 15, 2014.

  1. cylverbak

    cylverbak Member

    My 2006 Civic Hybrid (215,000 km) recently triggered an error code P0128. I took it in and after a careful inspection was told it was probably caused by the third-party instrument I had plugged in (ScanGaugeII) with the suggested course of action to remove it.

    Well, the ScanGaugeII has been there for at least 3 years with no problems, so I ignored the advice and plugged it back in. Within 80 km of highway driving my error code was back. During this time I started paying attention to the engine temperature which always settled at a steady 98° once fully warmed up.

    A couple of weeks later I took the car back in, removed the SGII (ok, maybe it really was the problem) and had Honda reset the error code - the SGII reported "no response" when I tried to reset the error that way.

    A couple of hundred kilometres later (without the SGII), the error code was back. Once more into Honda. This time they replaced both the thermostat and the sensor. The car ran for a couple of weeks with no further recurrence so I plugged the SGII back in and we've been fine ever since.

    Except now the engine temperature when fully warmed up is 89-90°. Doing some heavy browsing here seems to indicate that this new temperature is actually where it should be?

    I know that the Hybrid uses a different thermostat than the Civic so had the service manager confirm the part number that went in to the car - correct according to the paperwork. The Civic Hybrid uses 19301-RMX-306, the standard Civic 19301-RNA-306.
    Could someone tell me what the difference is and just reassure me that the engine is now running at the proper temperature.

    Thank you.
  2. S Keith

    S Keith Well-Known Member

    With the combined change of thermostat AND sensor, it's impossible to say for certain. It's possible that your old readings, which seem a little high to me, were due to a partial malfunction of both. I suspect that the code was triggered more by a malfunction of the sensor. It was likely sending erratic pulses that the ECM saw as out of range that likely don't show on the physical gauge or the Scangauge due to signal filtering.

    Many thermostats are rated for 180°F (82°C), so 89-90 is pretty typical as the coolant temp is always a little higher than the thermostat set temp.

    I don't have a scangauge, but I have a OBD-II reader and the paid Torque App. I'll check what it says tonight, but anything in the ranges we've been talking about sound fine to me.

  3. phoebeisis

    phoebeisis Well-Known Member

    100% of the time -ok maybe 99%-dealership mechanics/service writers will blame aftermarket add ons for various "engine drivetrain problems"

    They are probably 99.99% wrong when they are indicting a SG-
    Just shilling for the the manufacturer-
    the manufacturer online helpers are also quick to blame the SG or whatever
    Actual engineers-who we will never get to talk to-probably have a different take.

    Now some BS- like over oiled K&N filters-added for "better mpg and better performance" sure as heck DID cause some problems-killed the air sensors.
    And no aftermarket intake add on (modern ECM engines air and O2 sensors) has EVER improved PART THROTTLE mpg -
    They CAN'T!
    Safe bet MOST don't improve actual real world acceleration despite adding perhaps 3% peak HP
    No way some BS aftermarket intake can beat Honda OEM engineers(while remaining noise and pollution legal)

    Oh I am going sideways-pet peeve-aftermarket CAIs for "better FE and performance"-pure lying BS-
    It take LOTS of work to get better performance from current engines
    Or Nitrous oxide-best bang for buck-for $700 or so you actually get better acceleration
    Might break your engine-but it works

    Yeah I am a crank!!
  4. S Keith

    S Keith Well-Known Member

    Checked my '06 HCH2 with the OBD-II scanner and Torque Pro... Peaked at 94°C and settled on 91°C steady state.
  5. cylverbak

    cylverbak Member

    Thanks for checking. Other posts here mentioning thermostat temps seem to indicate 90° is pretty much the norm. I've never looked at the temperature until this error code came up so have no idea whether it's always ran this hot or was a recent malfunction.

    I understand that the sensor used is the same part number for both Civics and Civic Hybrids, but yes, changing over both at once does make it a bit dicey trying to interpret things.

    The Honda dealership here is a good one. I trust what they tell me and they've gone out of their way to assist or explain when I've got problems. I've been to a couple when travelling that I wouldn't trust as far as I could throw them.

    @ phoebeisis: sounds like you've been bit before. Been a long time since I've been run into problems like that. I'll just continue to keep my fingers crossed. :)
  6. S Keith

    S Keith Well-Known Member

    After further reflection, since you weren't paying attention before the issue, the 98°C steady reading may be above the threshold the ECU identifies as a thermostat/sensor failure or pending failure.

    Personally, I probably would have replaced the sensor too as you're getting into the high mileage/age range, and replacing it would be prudent.

    Last night's drive was just long enough to warm up. This morning's commute yielded the same results - 91°C.

    Happy Hybriding,

  7. cylverbak

    cylverbak Member

    My thought exactly.
  8. Dream'R

    Dream'R Well-Known Member

    The only thought I would add to the previous posts is to ask if the coolant has been flushed any time lately? The recommended intervals are very long and deterioration of the coolant can lead to clogged passages reducing the system's efficiency. I agree a temperature around 90C is typical. Replacing thermostats is almost a routine preventative measure.

    Glad to hear that you have over 200K on your hybrid.


  9. cylverbak

    cylverbak Member

    Most of the mileage (~3/4's) is highway driving. I've been following Honda's maintenance schedule so (I think) it's only been flushed once before. They flushed it when they replaced the thermostat.

    Love Honda. For the most part you put in gas and change the oil once in a while. Still purring and hope to get several more good years out of her. :)
  10. Harold

    Harold Well-Known Member

    Cylverbak are you still on the original pack.. I had a 2006 hch as well, but it ate rear tires. Honda replaced the upper control arms, but made the condition worse. The pack was starting too recalibrate often , but Honda service thought I was nuts. It would also fart often. I was getting near the end of the warranty so traded for a 14 Prius. Nobody else wanted my hch. I almost gave it away. No more Honda. Cars for me!!! H
    Last edited: Dec 21, 2014
  11. cylverbak

    cylverbak Member

    Hi Harold, I purchased new in May 2006. I've got the rear struts that were involved in the recall but didn't bother to replace them as I've never had a problem with the rear tires. My original Bridgestones were replaced after a normal lifespan of about 80,00 km I think. I ran them at 40/38 psi. I'd purchased Nokian Hakkapeliitta winters in the winter of 2006 and they are on at least 4 months of the year. I bought new summers at about 140,000 - Michelins but I'll get Nokian eTyres next time around.

    I'm still on the original battery pack and I don't think it's re-calibrating significantly more often. I didn't go with the extended warranty. This is a Honda. You don't need those things! :)

    I've been lurking these forums for years and have been following the problems some people are having. I know there are real problems out there, both mechanically and with dealers. I've been lucky on both scores. This car is treating me very well and I will get another when the time comes.

    The Prius is a nice car. My son loves his. If I had a dealer I trusted and did a lot of in-town driving I might have gone with one. I do a lot of long-distance driving and think the Civic Hybrid gives me more bang for my gas mileage buck - not nearly as nice for steady around town use though. The Prius shines there.
  12. Harold

    Harold Well-Known Member

    Hi Cylverbak . I had 11 yr. Extended warranty and was OK with the car up until the end of the warranty. I liked the car alot, but Honda service gave me no confidence.
    My gen 3 Prius gives me better fe in all conditions. Have managed 3 ltr. Per 100 kil out and back on one occasion with the Prius. I did manage 3.2 with the hch.
  13. Mendel Leisk

    Mendel Leisk 2010 Prius (CAN Touring) Staff Member

    Thermostats are a mechanical item, prone to wear-and-tear. I had one fail on an accord, it was opening too soon, making the car run too cold on highway. Maybe the opposite can happen. Sounds like you're good now. Assume those are all centigrade numbers.
    Last edited: Dec 22, 2014
  14. Harold

    Harold Well-Known Member

    I only had 7 years extended warranty not the 11 years I stated early on. H
  15. S Keith

    S Keith Well-Known Member

    I have had a number of thermostat fail across many vehicles over the years. I have had more fail "closed" than open, i.e., the cars overheat because the thermostat won't open.
  16. cylverbak

    cylverbak Member

    I've always thought that thermostats failed in a open position. Guess that's not always the case, which would explain the 98° I was getting.

    Centigrade numbers? Canada eh! :)
  17. jcp123

    jcp123 Caliente!

    Both of the failed thermostats I have had failed open, but yes, it can definitely fail and be stuck closed.
  18. EdwinTheMagnificent

    EdwinTheMagnificent Legend In His Mind

    I had one in my GLC fail , open of course. It happened during a 300 mile highway trip in December. Summertime , that sort of driving would result in 47-49 MPG , but this trip I only got 35 MPG.
    Way back in 1983 , I had a 1.2 mile commute to work. In nice weather I'd ride my bike. In rainy or snowy weather, I had a beater car (1973 AMC Hornet Sportabout). I convinced myself that the thermostat had failed , because I wasn't getting any heat. So I started to drain the radiator so I could change the thermostat. I was a bit surprised at the amount of coolant that drained ; almost nothing ! Maybe 8 0z. That's when I learned that the heater core actually needs hot coolant going thru it, not just hot air.
    I don't recall the engine ever giving any indication of overheating.
  19. RedylC94

    RedylC94 Well-Known Member

    The dealer volunteered to replace the original one in my GLC with a higher-temperature one under warranty, on the excuse that that might reduce engine "hesitation." The main effect of that change was making the radiator fan run more, since they didn't replace the fan thermostat with a correspondingly hotter one. Many years later I convinced myself the thermostat was sometimes failing to close, because the gauge sometimes didn't climb as high as normal. After I replaced the thermostat again, I realized the thermostat was still ok, and the only problem was that the gauge was erratic.

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