Well, this is a new one on me and to my OBD II scanner (also have a 99 VW New Beetle which has almost exhausted every code). I'm getting a an error code P0128: Coolant Temp Below Thermostat Regulating Temp.

The car seems to run just fine and no change in gas mileage or performance here. It threw this code once and upon inspection I noticed the coolant in the resevoir was below the Min line. I added coolant to bring it to just short of the Max line and reset the CEL. After driving for a couple weeks and maybe 1500 miles the light has come on again: the coolant level is just fine this time. The temerature gauge in the car is acting normally with the reading just halfway below the middle as it has for the last 75k miles.

It's my guess I could have a bad sensor somewhere. I don't know if this car has a thermostat, either, but I would think if it was acting up I would notice a longer than usual time to warm up or overheating which I don't.

Any ideas out there?

Thanks in advance!! :-)

Volvo for Life

I don't have a volvo, but I was looking for others with that same code of P0128. I took my car into the shop and they got that code. They said I need a new thermostat. Not sure if that goes across the board for all cars but figured I would share that bit of information in hopes that it will help you.

CA V40 - Did you ever find the answer to the P0128 Problem? Mine did the exact same thing. I put in a new ECT and it went off for a couple of days then came back on again.

Same code here on a 2002 S40. Anyone hear anything yet?

Thanks

2001 S40 85K-Have had all the same symptoms as everyone else except it seemed to clear itself when I was driving in TX and it was really really hot outside. I replaced the ECT sensor (~$65 from the dealer) Its the sensor right near the upper radiator hose and next to the serpentine belt guard. After replacing the sensor I cleared the code and it came back on a couple of days later. Guess next will be to change the thermostat (~$12 from the dealer). Will let the group know my results, hopefully that will take care of it. The manual says the coolant never has to be changed (find that difficult to take), but last option would be to flush the system and hope it's something to do with the coolant properties.

Hi, all, thanks for the responses!!! :)

I replaced my ECT fist which probably wasn't the problem? My temp gauge wasn't acting funny before replacement which may be a hint on a 2002 V40 the ECT is actually okay. I reset the Check Engine Light with my OBDII scanner afterwards. After about, I think, 8 cold starts the CEL came on, again.

I went to my dealer this last week and bought a new t-stat for I think about $26: genuine VOLVO part. (if someone does pay markedly less for a genuine VOVO one please let me know and I will have with the dealer!!!!)

The thermostat I installed yesteday, easy job. Th warm up seemed very normal after installation. Again, I reset the CEL with my scan tool. This morning I decided I would also as maybe a further reset disconnect and clean the battery terminal. I'm leaving the battery disconnected for about 8 hours.

I'll keep you posted on my results.

Ona related subject Prestone I happily discovered has a new antifreeze which they state will work with any color antifreeze either for a fresh fill or a top-up. Halelulah!!!!!!!! I paid $7.99 for a gallon at AutoZone in CA. It is also a pretty fluorescent green color. I'm going to stay with it because if any company knows more about antifreeze than ALL the car makers in the world it's Prestone.

Thanks, again, for your responses!!!

Well after all the time and effort it was the thermostat. I should have figured that when the check engine light went off in the extreme heat of Texas. The thermostat probably was opening up easier with the residual heat. I bought a thermostat for $6.85 at Autozone; it is the correct temp rating of 90 degrees C. I think $26 is a bit high, the dealer here in GA I swear said around $12. I only had to reuse the rubber gasket around the original thermostat which was in great condition. There was a noticeable difference in the spring rigidity between the new and old thermostat with the old one being a lot stiffer, thus probably not allowing as much coolant to flow. Final result is the check engine light has remained off and my OBD scanner registers a green and no default codes in the cars computer.

Thanks, Jester, for your reply and please let me know if your CEL stays off. On my car it took several cold starts for the CEl to light, again. It has not come back on since the t-stat was replaced. But,CA, with it's heat similar to TX, my t-stat could have been the problem.

I also now have sometimes hot or cold engine starting problems with rough running for a few seconds. Included was a cyl 1 and cyl 3 misfire from my OBD scanner a day ago. I'm not sure if this is a related problem to my error 128 or something new.

Please stay in touch. :)

Hi all,... I'm an auto technician here in NH with over 30 years exp. and am having the same problem with a customers S40.....a 2003 with a 1.9 turbo

the code p0128 keeps coming back. i've already replaced both the thermostat and the ect. this last time i noticed the fault data for the ect was at -40 deg when the code occured, which is what you'll get with an open ECT circuit .....it's been cold here but not that cold...i've checked all the connections and haven't found anything yet.

while researching the problem i found this is a common issue with this car. it's also how i found this forum.

Any ideas?

I had the same error code in my 2001 V40. The car is now fine after replacing both the thermostat and the temperature sensor.

I took mine to Volvo and they told me it was the thermostat, ECT unit, Camshaft reset valve and the CVVT unit.

So did you get all that replaced? What did that cost?

Thanks

I have been battling a check engine light issue since purchasing my used 2003 S40 from a dealership last May. They originally replaced an ignition harness because the onboard computer had registered multiple misfires and a known keyring issue was identified. The very next day the light came back on and then went out for several months.

As winter set in the light reappeared right after refueling. I suspected that the gas cap may not have been put on properly since this has happened on my Dodge. I reseated the gas cap and waited for the onboard computer to clear the code. It didn't. I decided to monitor carefully and only noticed the occasional rough start while firing and jerky shifts from 1st to 2nd. Both were in extreme cold.

I finally purchased an OBDII reader which identified four codes. The first was a P0442 (evaporative emmision system leak detected - small leak. The second was a P0128 (ECT sensor, faulty signal), the third a P0456 (evaporative emmision system leak) and finally another P0128. After reading several forums I elected to replace the gas cap and erase the codes. So far nothing has returned.

Since several people are reporting the P0128 with thermal extremes and no correlation to high or low engine temperatures (not to mention no unusual engine vibrations) I suspect that this might simply be a thermal expansion phenomenon tripping false readings on the ECT sensor. Can anyone qualify my thoughts here?

(... this is why we do "burn-in" testing in the electronic industry)

 VolvoV40Cooling_system1.9Turbo.pdf ( 361.91k ) Number of downloads: 168
I have a V40 1.9 turbo 2002 (75000 miles).

I started getting a "check engine lights" as most of us do when we get to this post :) .
I went to a discount auto parts to buy a OBDII scanner and the cheapest was at $59. Not willing to pay for reading a code , the attendant nicely went out and read the P0128 code. He got from his book the related problem something like a " temperature of coolant below normal range" .
I decided to bring it to the local mechanic which asked me for $89 to read the code not applicable to any repair !! I said have a nice day.

At that point , I read posts on this forum plus the ODBII code suggested solution for the P0128 code.

I went to the Volvo dealer and asked for a thermostat (seemed to be the first on the list !!) . I asked the attendant if she had a map of the parts and their location ( I had no clue) in the engine. She gladly printed out the "detailed map " (see attached to this post) and as I was paying the cashier one of the mechanic was asking for the same part . He indicated that if I was about to change the thermstat and its seal (23,24 ) , I should change as well the ECT (21) and he mentioned to be careful and not to loose the ring (22) as it is not included with the new ECT. He said that I would loose quite a bit of coolant during this process. So I bought a gallon of coolant.

I better keep my day job as he took me a couple of hours to remove a few screws. Well, I had a little problem with part 27 and especially that da.. screw (28). The head was damaged and I had a trip removing it. Anyway, to screw (21) on (20) that was a lot of fun too. No space to really tight good the screw!!

Anyway, I did not loose much coolant and my "check engine light" has come off after a couple day of running the car.
Total cost :
Thermostat : ~$26
Coolant: $22
ECt: 76 $
2 screws(28) : $1.5
Total around : $130 ( not counting the borrowing of tools from my neighboor) . Not only you need to have tools but you have to own the right ones that will work around your engine!!

Enjoy
Chris (Miramar,Fl)undefined

I replaced my thermostat and that did not help at all. I then purchase a replacement ECT from IPD.

http://www.ipdusa.com/Volvo-S40V40-2000-20.../p-82-428-1347/

I haven't installed it yet. I'll update after it's done.