po128 code ?
 

Hello
engine light came on
so read the code on the ob reader i have po128
read in the maual coolant thermostat ...
so checked the coolant...
it was empty..so right now added coolant and cleared the code..
started the car in the garage for a bit and engine light is off
,,my guess is to monitor the engine light to see if it comes on again
as i read it could of been thermostat or sensor...
so hopefully it just needed coolant

thoughts
thanks
2002 s40 volvo

adding
 

so im guessing as i was very low on coolant,,this would bring on the engine light? correct
even though the temperature guage was at operating level, between the low and the high

thanks

Yes, if the coolant is low enough such it isn't covering the sensor you can have false readings.

However, considering the location of the sensor on the 1.9L engine, I don't think this was it unless you are talking very low.

The coolant temp below thermostat regulating temperature is a common issue.

thanks for the response
 

you can see a little bit of coolant at the bottom of the resoviour

Then I'd say it wasn't low enough to cause an issue.

Search threads for the temp sensor replacement. It is a very easy DIY fix.

response
 

well it has been a few days now
and the engine light has not come on..so im thinking everything is back to normal after adding coolant

update
 

- well after i cleared the code and now its been just over a week,,the engine light came back,,,coolant level is the same
code P0 128 is back

would you now say to change
thermostat ans sensor
or just thermostat
thanks

update
 

well...today sunday changed the thermostat..as tech mentioned ina another thread easy job..and it was
- volvo was closed today sunday..so went to canadain tire here in canada bought the thermostat and they had 187 and 190 temperature..bought the 190,,a little more money
- unfortunately all stores i called,,did not have a coolant temperature sensor,,,when changing the thermasta i saw where that is,,easy change as well it appers...
cleared the code,,will see how the car is withe new thermostat

I'm interested to see if this works out.

I've changed the sensor twice now and both times the temp gauge looks okay, but the code indicating a low temp is thrown. It has started again, so I'm thinking of changing to the 190 thermostat to see if that gets the temp high enough.

mon feb 21
 

well ,,engine light is still off
but checkked the car and just noticed the rad fluis is once again low,,,,
just added a couple of weeks ago

does not seem anywher that there is a coolant leak
what could cause the fluid to go low in just a couple of weeks
thanks
just changed the thermostat 2 weels ago

update
 

well just checked the oil dipstick and it seemed there was too much oil...its not milky.but a bit runny .read alot of posts mentioning maybe coolant went into the engine ..
bringing the car to shop tomorrow,,im freaking out

Sorry to hear that. The coolant isn't evaporating so it is going someplace. However, I'd think that the oil would get milky almost immediately.

Since you are going to the shop, ask about a technical service bulletin (TSB) to update the ECM to fix the P0128 code. I tried "justask" (you pay to get an answer) and the answer was that there was a TSB but he didn't list the number.

Good luck; I hope that maybe it was just overserviced and you have a loose radiator hose.

response
 

took the car in
volvo called and said nothing is wrong withe car....
they pressure tested it for leaks etc....
now im stumped...just thinking i just added coolant to the resivouir,,maybe i should of added coolant to the rad as well...dont know..

volvo just saifd keep an eye on it

Could it have been air lock? I can't remember if Volvo utilizes an air bleed for cooling system.

picked up vehicle
 

what i did notice is
following the volvo with my car is that the volvo had a alot of exhaust compared to other cars on the road,,not sure if this would mean anything of why the coolant was low
thoughts

Assuming it was fully warmed up, then it would appear something is being burned off.

oil is blue -ish
coolant would be white

I went to the local dealer Southbay Volvo and they said there wasn't a service bulletin. I followed up with the expert and got Tech journal 19803 or older tech net note 25-18.

Considering the run around I had with the dealer on an airbag issue (V-bad airbag, me- did you check the connector, V-yes...replaced airbag, V- bad connector, me- great refund the airbag cost, V-the airbag tests bad, me-let me see it, V-here it is, me- it is popped; of course it will test bad after you set it off. )

Please ask your dealer about the technial journal.

Here is the tech net note on the code.

P0128 is a general code linked to Volvo ECM DTC A1. Also the tech note says that the normal operating temp should be about 90C. So, I'm thinking that if you use a 87C thermostat (normal) you are on the edge of it being too low.

Much of our driving in the morning is low speed (20 mph) and stopped (idle) so I'm thinking that this may be the issue with our V-40.

P0128 in my world
 

Hello, I have had a P0128 in my 2002 V70 for a month. Finally got around to changing my thermostat today February 27th with an OE (Wahler) from one of the site sponsors. My gauge ran low during all this period so the P0128 code was a perfect match. I'll get back to you on this board if anything changes my happy state of mind. CHEERS, Kira

Although my thermostat was less then a year old, I pulled it to check and found it broken. The local auto parts store had aftermarket items so I decided to get a 91 degree item instead of the 90.

The gauge now shows one increment higher. Since the average mph for the last two tanks was only 16 mph, it it trips again I'll take it in for the tech note ECM upgrade.