Calling ALL 'Codebreakers' - United Bimmer Community

**Timboy** · 12-14-2005, 12:10 PM

Here in the state of Georgia we are required to have our cars tested for emissions every year. Yesterday my car failed the test.

Never had this happen before. The test detected an onboard diagnostic code of P0128..... Anyone know if this is a failure of the O2 sensor????
The car is getting it's 60,000 mile checkup on Friday anyway. I was just curious as to what that code meant.

Thanks

**komodo** · 12-14-2005, 01:21 PM

P0128 is Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)

Now I personally don't know much about the coolant system inside a car, but hopefully this will tip off someone who does. Maybe the thermostat is broken that reads the temp of the coolant? Is there any kind of heater in there that could be malfunctioning?

Unfortunately it doesn't sound as easy as an O2 sensor.

**Numark318i** · 12-14-2005, 07:17 PM

whys this in teh e46 area?

nick_318is · 12-14-2005, 07:22 PM

^2001 330ci

**c1apton** · 12-14-2005, 07:27 PM

Was the car up to normal operating temp? If they tested while cold or still "warming up" they'll get a "rich" reading. Sounds like "operator error" if the above is the case. Does your temp guage read "dead center" or near that point? If not, especially on the low side, car will run rich and not pass emissions.

**Numark318i** · 12-14-2005, 07:27 PM

oh.....for some odd reason i thought Komodo wrote that.
my bad

**Timboy** · 12-14-2005, 10:05 PM

Car had been running for about an hour, temp hand was dead center, and there has never been a heat/heater or coolant problem.....

**c1apton** · 12-15-2005, 04:07 AM

Ok, then try this before any mechanicals. Get your self a small bottle of STP gas treatment and put in tank & fill tank up. Also clean you MAF and make sure air filter is clean. Most inspection places are questionable and can easily be at fault. Other options: get a second opinion from another inspection place or at a dealer. Just trying to save you $$$ before someone(inspection place) gives you advice via their asses. They tend to see $$$ when a BMW rolls in.

**Timboy** · 12-15-2005, 04:09 PM

Thanks C1apton.............

**Antiburn** · 12-19-2005, 04:34 PM

Thermostats on BMW can throw faults. BMW's are designed in such a way that your thermostat helps regulate your emissions output. If its engines a little hotter then usual due to your thermostat not opening correctly your Nox emissions will rise which will cause your car to fail, like it did. Only way around it is to replaced your thermostat, I believe they go for 115$ or so. Its a ridicilously easy job so if you want to do it yourself you just need a few tools.