Excuse the lack of correct terminology but I am a girl with limited car knowledge who is sick of being taken for a ride by the dealer so I want to know some of your opinions. I have read so many posts on the P2181 code but no one actually says what the root of the problem is.

New to me 04 Audi A4 1.8T bought with no light on. Had for two days and while driving to work when I accelerated on the highway my check engine light popped on. Drove right to Autozone where the code was ran P2181. Checked the coolant and it was a little low so added coolant and cleared the code. The code stayed off until the next morning at the same spot on the highway it popped on. Took it back to the dealer. They replaced the etc sensor and checked for leaks which there were none. Code was cleared. It remained off for three days while driving around town. On Monday driving to work around the same spot on the highway it popped on again. Stopped by Autozone and its the same code.

This story is the same all over the forum but what no one actually says is what keeps the code off if anything. The temp gauge reads as it should and never gets above the middle. Coolant level is good and there are no leaks. I even put cardboard under the car to check.

I don't want to continue getting charged huge rates by dealers to check for things if my light is just going to come back on. They see a female and see money.

So my questions

Has anyone found a way to keep the light off? If so what was replaced?

Am I safe to drive it since my temp gauge is reading fine and coolant level is fine?

Thanks

 

P2181- Performance malfunction in the cooling system

If the dealer already replaced the engine coolant temperature sender we can rule that out as the problem. You have no discernible leaks and coolant level seems constant.

Check to see if your heat and a/c work and report back. Yeah I know it sounds silly but it can help us better diagnose.

 

The ac and heat work beautifully. I live in Florida so I'd notice if the ac didn't work In fact my ac has been on when this happens.

Starting to notice a little loss in power until I reach about 40mph.

Thanks

 

Well, unfortunately the news is not good. Without having your car to look at there is no way to be certain, and even then its iffy. I would recommend that you look for an independent shop in your area that specializes in German cars or Audis specifically. I find the yellow pages to be better than trying the intarwebs. Have them check it out. Based on your symptoms either nothing is wrong and you have an electrical gremlin or something in your coolant system isn't happy ie: thermostat/water pump. If its the latter you are looking at a significant repair bill.

Good luck, keep us updated

 

I spent some time investigating the P2128 code popups of my wife's 2003 Audi TT with 45K miles. Odd thing was the P2128 code would popup at specific street locations! Because I'm an electrical engineer, I thought of electrical interference from a nearby transmitter was affecting an Audi sensor circuitry. At one time, I'd drive over a small bridge in Montecito, CA and the P2128 code popups occurred with a very high degree of predictability.

The sensitivity problem is most likely related to the high impedance (electrical resistance) of the coolant tank fluid sensor probes with a fluid resistance measurement of well over several hundred thousand Ohms. The wiring of this circuitry could easily pickup high frequency radio signals and end up creating a detected (or rectified) bias voltage at the sensor input circuitry; causing the false trips. My fiddling around of the sensor connector stopped the P2128 popups for a few months. I probably managed to "clean" the probe connector contacts in the process of connecting and disconnecting the probe connector located on the tank. Because the circuit is high impedance and very low current, the connector contacts are less "self cleaning," and susceptible to making poor electrical connections.

Recommendations:

1. Use tap water that hopefully contains a sufficient amount of minerals to lower the sensor circuit electrical resistance. Don't use "purified" water ... only use the stuff out of the water hose.
2. Don't use more antifreeze than required. Too much antifreeze will increase the electrical resistance of the coolant solution.
3. My coolant sensor probes have always remained clean. But if your probes are not clean, then clean them.
4. The sensor wire cable should be shielded (using a grounded, braided shield) to prevent radio frequency interference problems.

 

Yes, your car is most likely safe to drive with the coolant level and temp gauge readings OK. The problem is most likely in the monitoring system itself ... a case of poor engineering.

 

Has this issue been resolved? If not, I may have another theory to add to the mystery of this evil code.

 

Repin the terminals of the coolant temp sensor, and replace the thermostat. Code will set If the voltage drops out temporarily (sensor or terminal connection problem) or if the cooling system does not reach a set temperature within a set period of time/ accumulated air flow ie: thermostat